Solid-phase extraction in the determination of gold, palladium, and platinum

1249 J. Sep. Sci. 2012, 35, 1249–1265 Elisaveta Mladenova Irina Karadjova Dimiter L. Tsalev Faculty of Chemistry, University of Sofia “St. Kliment Ohridski” , Sofia, Bulgaria Received October 21, 2011 Revised January 13, 2012 Accepted January 23, 2012 Review Article Solid-phase extraction in the determination of gold, palladium, and platinum A simple classification of various sorbents and solid-phase extraction procedures used for preconcentration of trace levels of Au, Pd, and Pt from different sample types is proposed in this review article. The large variety of available sorbents/procedures has been organized according to expected mechanisms of sorption process (complex formation; ion exchange; adsorption; ion-imprinted or molecularly imprinted polymers); according to the kind of monomeric units of the polymer matrix as well as on the basis of the kind of functional group responsible for main performance characteristics (selectivity, capacity) of the sorbent. Advantages of chemically modified sorbents, sulfur-containing sorbent extractants, and ion-imprinted polymers, together with rational pretreatment by means of microwave treatments, scaling down of enrichment, and quantification by means of flow and flow injection approaches are given. Preferred instrumental techniques for quantification of ppb levels of Au, Pd, and Pt in prepared concentrates/column eluates are multielement instrumental techniques: inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICPMS). Excellent limits of detection at picogram levels of these analytes are provided by electrothermal atomic absorption spectrometry (ETAAS), generally in single-element mode and the neutron activation analysis (NAA), while X-ray fluorescence spectrometry and flame AAS are rarely applied because of lack of sensitivity at sub-ppm levels of Au, Pd, and Pt. Some problems of atomic spectrometric quantification techniques and their representative limits of detection are given. Recent applications to geological, industrial, pharmaceutical, biological, and other materials are tabulated. References have been selected mostly from the period 1995 to 2010. Keywords: Noble metals / Preconcentration / Solid-phase extraction / Sorbents / Trace analysis DOI 10.1002/jssc.201100885 1 Introduction Correspondence: Ms Elisaveta Mladenova, Faculty of Chemistry, University of Sofia “St. Kliment Ohridski”, 1 James Bourchier Blvd., Sofia 1164, Bulgaria E-mail: elimladenova@chem.uni-sofia.bg Fax: +359 2 9625438 Abbreviations: AAS, atomic absorption spectrometry; AC, activated carbon; APDC, ammonium pyrrolidinedithiocarbamate; CMDTC, bis(carboxymethyl)dithiocarbamate; D2EHPA, di-2-ethylhexylphosphoric acid; DMG, dimithylglyoxime; ETAAS, electrothermal atomic absorption spectrometry; FA, fire assay; FAAS, flame AAS; GFAAS, graphite furnace atomic absorption spectrometry; ICPMS, inductively coupled plasma mass spectrometry; ICP-OES, inductively coupled plasma optical emission spectrometry; ID, isotope dilution; IDMS, isotope dilution mass spectrometry; IEX, ion exchange; IIP, ion imprinted polymer; ILOD, instrumental limit of detection; KR, knotted reactor; LLE, liquid–liquid extraction; MIP, molecularly imprinted polymer; NAA, neutron activation analysis; PCDT, pyrrolidine carbodithioate; PGE, platinum group element; PGM, platinum group metal; PTFE, poly(tetrafluoroethylene); PU, polyurethane; PUF, polyurethane foam; PVC, polyvinylchloride; XRF, X-ray fluorescence spectrometry  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Nanotrace (10−9 g) and picotrace (10−12 g) levels of Au, Pd, Pt play an important role in various processes because of their catalytic and biological effects, high prices, gradual accumulation as emerging pollutants, (nano)technological pollution, needs for better utilization of raw materials, and industrial waste, etc. The determination of noble metals at these concentration levels is still a serious analytical challenge because of very unfavorable matrix-to-analyte ratios and interference effects. Typical analytical procedures commonly include a step of sample pretreatment (such as alkaline fusion, dry ashing, wet digestion, microwave-assisted decomposition), followed by efficient enrichment and separation from complex matrices and interferents and instrumental measurement of target analytes. Various preconcentration approaches have been documented in previous books and reviews: semiquantitative fire assay (FA), liquid–liquid extraction (LLE), solid-phase extraction (SPE), precipitation and coprecipitation, etc. [1–3]. Quantitative sorption using various intact or modified sorbents with suitable functional groups has proved very efficient owing to its high enrichment factors, low/no solvent consumption, clean extracts, and easy automation. The www.jss-journal.com 1250 E. Mladenova et al. relevant functional groups are (mostly) covalent bound to the insoluble polymer matrix, hence the sorbent is not lost in the aqueous phase. In favorite cases, sorbents can be regenerated and multiply used, although there are problems caused by aggressive acidic solutions, slow reaction kinetics of sorption/elution, memory, and carryover effects. Enrichment efficiency and selectivity could be improved by increasing porosity and/or dispersity of sorbents, better cross linkage, use of efficient, complex-forming eluents, application of microwave or ultrasound, and other modern approaches. Careful optimization of several chemical and instrumental parameters is essential: concentration of acid(s), temperature, contact time, flow rates for sorption, and elution. Among the most reliable and sensitive analytical techniques for quantification of noble metals after enrichment are multielement instrumental techniques inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). Excellent limits of detection (LODs) are provided by electrothermal atomic spectrometry (ETAAS), also known as graphite furnace AAS (GFAAS), generally in single-element mode and the neutron activation analysis (NAA). The X-ray fluorescence spectrometry (XRF) and flame AAS (FAAS) are rarely applied because of lack of sensitivity at sub-ppm levels of Au, Pd, and Pt. The aim of this review is to present a simple and practical classification of sorbents used for Au, Pd, and Pt enrichment from various sample types. J. Sep. Sci. 2012, 35, 1249–1265 performance characteristics of the sorbent (selectivity, capacity): N-containing; S-containing; O-containing; P-containing; carbon-based (activated carbon (AC), fullerenes); TiO2 ; Al2 O3 ; miscellaneous The sorbents with immobilized functional groups could be synthesized either by direct polycondensation/polymerization from monomers containing a target functional group or by appropriate chemical modification of existing polymers. Linear polymer sorbents are unstable in acidic and alkaline media as well as in the presence of organic solvents. Sorbents with three-dimensional structure are more stabile in aggressive reaction media (typical for sample preparation procedures) and could be regenerated more easily. The cross-linked polymer sorbents with hydrophobic matrix are often preferred owing to their better chemical stability and mechanical strength. Sorbents with macroporous structure exhibit higher sorption capacity and better kinetic properties. Fiber-shaped sorbents could be advantageous versus granular resins owing to their larger surface area, possibility for using higher flow rates, and better kinetic characteristics. Sorbents on inorganic support exhibit high mechanical strength as well as thermal and chemical stability; on the other hand, their capabilities for functionalization and their sorption capacity are more limited versus polymer/copolymer supports. Silica gelbased sorbents are also chemically and mechanically stable to organic solvents and mineral acid solutions [4]. The main performance characteristics of resins will be reviewed following the above classification. 2 Sorbents Classification of sorbents for SPE of Au, Pd, and Pt cannot be complete and straightforward, since mechanisms of sorption are not always well established and verified. The matrix of sorbent can be homopolymer or copolymer, various crosslinking agents could be utilized with same monomers, or otherwise the same polymers could be functionalized with different derivatives of the same class of chemical reagents. A simple, generalized classification of sorbents for SPE preconcentration of Au, Pd, and Pt is presented below: (i) According to mechanism of sorption process: complex formation; ion exchange (IEX); adsorption; ion-imprinted or molecularly imprinted polymers (IIP/MIP). (ii) According to the kind of monomeric units of the polymer matrix: silica gel; cellulose; acrylonitrile or its ester; vinylbenzylchloride; styrene (pure, aminopolystyrene, or chloromethylated); divinylbenzene (pure or chloromethylated); polyamine–polyurea; vinylpyridine (pure or substituted); dehydrodithizone; polyurethane (PU); vinyl alcohol; phenolformaldehyde; substituted piperazines; diethylenetriamine (pure or substituted); phenylene; sulfonic acid; phosphoric acid; aminocarboxylic acids; chitosan; fullerene С60 . (iii) The most adequate and reliable classification would rely on the kind of functional group responsible for main  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 2.1 N-containing sorbents for preconcentration of Au, Pd, and Pt The N-type of sorbents represent a widely used group of materials for SPE not only for noble metals but also for many other analytes. They could act by both mechanisms of complex formation and ion exchange. Usually the N-containing centre is additionally linked to a polymer matrix. For example, the matrix could be cellulose, functionalized with 1-(2′ hydroxyphenylazo)-2-naphthol (Hyphan) [4]. Cellulose could be functionalized with quaternary alkyl substituted amino groups (Cellex-T) participating in IEX [5,6]. The cellulose matrix is a common material in comparative studies of various SPE sorbents. Cellex-T exhibits lower capacity than some styrene– divinylbenzene sorbents but allows higher enrichment factors [7, 8]. Cellex-T could be functionalized with green algae Chlorella vulgaris for selective enrichment of Pd and Pt from acidic media [9], thus forming a kind of biosorbent. Comparative evaluation of sorbents on cellulose base, functionalized with various complexing agents such as oxime, sulphoxine, and 2,2′ -dimethylaminodimethylamine has been performed [10]. These sorbents call for prereduction of platinum ions to Pt(II) by means of iodide or sulfite ions. www.jss-journal.com J. Sep. Sci. 2012, 35, 1249–1265 Basargin et al. have synthesized complex-forming sorbents based on aminopolystyrene azo components and various para-substituted anilines [11]. Metalfix Сhelamin is a tetraethylenepentamine complexforming resin [12−15]. The noble metal ions (Au, Pd, and Pt) are strongly complexed and could hardly be eluted, even from resin with larger particle size [14]. Therefore, procedures rely of digestion of sorbents followed by instrumental measurement. Metalfix Сhelamin has been applied in determinations of Au, Pd, and Pt in various samples with complex matrices like rocks, silicates, iron ores, etc. [12−15]. Dimithylglyoxime (DMG) and its derivatives have also been applied as reagents for functionalizing complex-forming N-type resins. Various supports such as polyacryl ester (Amberlite XAD-7) [16, 17] or silica gel [18] have been used. Silica gel has often been used as a support for chelating resins for Au, Pd, and Pt enrichment. Selectivity of sorbent could be provided by appropriate functionalization. Separon SGX C18 is a porous spherical C18 silica gel. This sorbent is working in the presence of surfactants such as dimethyllaurylbenzylammonium bromide [19] or [1-(ethoxycarbonyl)pentadecyl]trimethylammonium bromide and benzyl(dodecyl)dimethylammonium bromide [20]. The complexing agent, e.g. tetrabutylammonium [21], is usually added before passing solutions through the SPE column hence “softer” conditions are used versus traditional LLE. Epoxy-imidazole resin [22], epoxy-polyamide resin [23], polyacrylaminoimidazole fibers [24], poly(acryldinitro phenylamidrazone-dinitroacrylphenylhydrazine) chelating fibre [25], 1,5-diphenylcarbazone-naphthalene [26], cyclam (1,4,8,11-tetraazacyclotetradecane) on a vinylnenzyl chloride– divinylbenzene copolymer [27], as well as polyvinyl chloride functionalized with cyanoethylamine and ethylenediamine [28] have all been applied for enrichment of Au, Pd, and Pt. However, some of these sorbents are relatively short lived, e.g. less than 10 working cycles [24]. A large group of sorbents for preconcentration of gold and platinum group elements are the so-called POLYORGS. They have been synthesized, characterized, and successfully applied by scientists from the Russian Academy of Sciences [29]. These sorbents contain a chemically bound active ligand on a polymer matrix. POLYORGS are chemically stable within a broad pH interval as well as in boiling solutions. Their main characteristics are compiled in Table 1, while useful details are given in original publications [29–39]. The complex-forming mechanisms appear to prevail, although the POLYORGS XVI could also act by anion exchange mechanism [38]. Molybdenum(VI) and Rh(III) are also sorbed on POLYORGS XI but do not interfere with the subsequent XRF quantification [35]. The brand Purolite resins have also been applied for SPE of noble metals from solutions. Purolite S920 and Purolite S924 are polystyrene-based resins modified with thiourea and thiol, respectively. Purolite S984 is a polyacrylic resin functionalized with polyethylenepolyamine [40]. In most cases, careful optimization of chemical conditions for SPE has allowed selective enrichment in the presence of concomitant  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Sample Preparation 1251 ions such as Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. All above-mentioned sorbents are selective for Au(III), Pd(II), and Pt(IV), except for epoxypolyamide resin [23] being selective for Pd(IV) only. The complex-forming mechanism is typical for all above-mentioned N-type sorbents. Some N-type resins for Au, Pd, and Pt are working on anion exchange mechanism. Several brands of sorbents (Duolite, Amberlite, Dowex, etc.) with primary, secondary, tertiary, and quaternary amine functional groups are available. They could be distinguished as weakly, intermediate, and strongly basic anion exchangers. Several essential characteristics of these sorbents are given in Table 2. Generally, the matrix is phenolformaldehyde resin or styrene polymer. Resins with primary, secondary, and tertiary amino groups are behaving as weakly basic (weak anion exchangers). Sorbents with quaternary ammonium groups exhibit intermediate basic properties, while sorbents with nitrogen heterocycle functional groups are strongly basic anion exchangers. The capacity of weakly, intermediate, and strongly basic anion exchange resins is decreased at increased HCl concentration in sample solution. Complete equilibration between the aqueous phase and the resin is attained after as long as 7200 s, although reaction times between 60 and 1000 s contribute most significantly to sorption yields. Palladium(II) is sorbed as negatively charged, hydrated chloride complexes [PdCln (H2 O)4–n ]2–n [41]. For HNO3 solutions and intermediate basic resins, however, the effect of acid concentration is reversed [41]. Observations on the effect of HCl concentration for weakly basic anion exchangers have been confirmed by another group of scientists and have been explained by concurrent sorption of Cl− and HCl2 − instead of the targeted [PdCl4 ]2− complex [47]. Moreover, shorter equilibration times (1800 s) were used, yet with selectivity impairment [41]. Amberlite IRA 35 sorbent has proved efficient and selective for enrichment of Au(III), Pd(II), and Pt(IV) from complex solutions containing other metal ions and salts [43]. The Dowex brand sorbents have been applied for preconcentration of Au and platinum group metals (PGMs). Dowex 1-X10 and Dowex 1-X8 resins contain quaternary ammonium ions as functional groups that results in higher capacity versus sorbents with nonionic functional groups, e.g. versus Amberlite IRN 78 [48]. Palladium and Pt have been extracted from road dust by Dowex 1-X10 resin that contains methylammonium functional groups. The LODs have been improved by applying multiple elutions with hot eluent agent [49]. The Dowex 1-X8 resin has been utilized for enrichment of noble metals from geological samples [50, 51], for Pd from copper ores and concentrates [52], and for Pd and Pt from environmental samples [53–55]. Kolarik and Renard have found that Pd(II) in 6 mol/L HNO3 exhibits strong affinity to bounding with 4-(N,Ndimethylbenzimidazol)phenyl but cannot provide IEX even after 20 h contact at 60⬚C. The sorption of Pd(II) from 6 mol/L HNO3 from similar tertiary and quaternary anion exchangers is less efficient but the IEX equilibrium could be obtained faster − for 1 h at 60⬚C or even shorter times with www.jss-journal.com 1252 J. Sep. Sci. 2012, 35, 1249–1265 E. Mladenova et al. Table 1. Characteristics of POLYORGS sorbents Sorbent Polymeric matrix Sorbent physical form Analyte and capacity mg mL−1 References POLYORGS IV Copolymer styrene–divinylbenzene (10%) Granules Au, Pd, Pt [30–32] POLYORGS V Polystyrene Powder Au 340, Pd 18.4, Pt [33] POLYORGS VI Polyvinylalcohol Fibres Pt, Pd [34] POLYORGS XI Copolymer N-vinylbenzimidazole–divinylbenzene (8%) Granules Au 990, Pd 299, Pt 296 [35] POLYORGS XI-N Copolymer N-vinylbenzimidazole–divinylbenzene (8%) Fibrous “filled” material Au 500a) , Pd 150a) , Pt 145a) [36, 37] POLYORGS XV Copolymer glycidylmetacrylate– ethylenedimethacrylate (40%) Granules Au, Pd, Pt [29] POLYORGS XVI Copolymer glycidylmetacrylate– ethylenedimethacrylate (40%) Granules Au [38] POLYORGS XVII Copolymer styrene– divinylbenzene (10%) Granules Au, Pt, Pd [39] POLYORGS XXI Formaldehyde condensate Powder Au, Pt, Pd [29] Copolymer glycidylmethacrylate– ethylenedimethacrylate (40%) Granules Au [29] POLYORGS XXII Complexing group -NH-NH2 a) Sorbent capacity data from [36].  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com Sample Preparation J. Sep. Sci. 2012, 35, 1249–1265 1253 Table 2. Characteristics of some N-containing anion exchange sorbents for Au, Pd, and Pt Brand Functional group Matrix Basic character Sorbent structure Capacity meq mL−1 Duolite A6 Duolite A7 Tertiary amino groups Primary, secondary, and tertiary amino groups Secondary and tertiary amino groups Tertiary amino groups Phenol– formaldehyde Phenol– formaldehyde Weak Macroporous Weak Macroporous Phenol– formaldehyde Weak Macroporous Tertiary amino groups Tertiary amino groups Aminodiacetate groups Polyamine groups Acrylic gel Duolite S 37 Amberlite IRА 35 Amberlite IRА 67 Amberlite IRА 93 Amberlite IRC 718 Diaion CR 20 Duolite ES 346 Duolite A 30 В Duolite C 467 Lewatit MP 500 A Varion AP Aminophosphonium groups Tertiary amine and quaternary ammonium groups Amidoxime groups Quaternary ammonium groups Pyridine groups Working pH Upper temperature limit [K] Sorbed analyte ion References 2.4 333 Pd(II) [41] 2.5 313 Pd(II) [41] Pt(IV) [42] [43, 44] 363 Au(III), Pd(II), Pt(IV) Pt(IV) 363 Pd, Pt, Pt(IV) Pd(II) [47] Pt(IV) [45] 313 Pd(II) [47] 353 Pd(II) [41] 363 Pd(II) [47] 343 Pd(II) [41] 338 Pd(II) [41] Weak Weak 1.6 0–7 Weak Polystyrene Weak Macroporous Polystyrene Weak Polystyrene Intermediate Macroporous 1.11 Epoxypolyamine Intermediate Macroporous 2.6 Polystyrene Intermediate Macroporous 1.0 Styrene– Intermediate divinylbenzene Styrene– Strong divinylbenzene Macroporous 1.1 Macroporous 1.3 some sorbents such as Dowex 1 × 8 and Amberlite IRN 78 [56]. The resins Amberlite XAD-2 and Amberlite XAD-8 are based on hyper cross-linked styrene–divinylbenzene polymers. The schemes of sorption of Pd(II) and Pt(II) on Amberlite XAD-2 and Amberlite XAD-8 are shown below [57]. For monoamines [57]: PdCl4 2− (aq) + 2 RNH3 + (aq) → (PdCl4 2− )(RNH3 + )2(aq) → (PdCl4 2− )(RNH3 + )2(sorb) RNH3 + (aq) + Cl− (aq) → (RNH3 + )(Cl− )(sorb) (1) (2) 2 (RNH3 + )(Cl− )(sorb) + PdCl4 2− (aq) → (PdCl4 2− )(RNH3 + )2(sorb) + 2Cl− (aq) (3) For triamines [57]: PdCl4 2− (aq) + RNH+ (CH2 CH2 NH3 + )2(aq) + Cl− (aq) → → (RNH+ (CH2 CH2 NH3 + )2 )(PdCl4 2− )(Cl− )(sorb)  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim (4) 1.0 1.5–14 0–13 0–14 1–7 [45] [45, 46] Aliphatic protonated mono- and triamines are added to the analytical solutions in order to bind the negatively charged chloride complexes of Pd and Pt from HCl solutions. The formed ion association amine complexes are then sorbed on the resin. Analyte recovery depends on both hydrophobic properties of the amine and the sorbent and on the sorption behavior of the amine by itself. The ions of these noble metals are sorbed in a similar way on Cellex P after pretreatment of analyzed solutions with ethylenediamine [58] or diaminopropane [59]. Comparative evaluation of the efficiency of IEX resins and amphoteric exchangers [60] has shown that the former type of sorbents exhibit better IEX capacity as well as faster IEX versus the amphoteric type. The physical form of the amphoteric exchanger also plays an important role – granules with smaller diameter perform better. The application of IEX resins for sorption of noble metals is widely used in hydrometallurgy (for recovery of precious metals from refinery plant effluents, from automobile catalytic converters, from liquid radioactive waste, etc.) [61,62]. Macroreticular polystyrene-type strong base anion exchange resin (with a quaternary ammonium group) has been www.jss-journal.com 1254 E. Mladenova et al. successfully applied for adsorption of noble metals from industrial multicomponent solutions [63]. The introduction of IEX resins to the gold mining industry has been supported by several fundamental studies in the field: investigations on adsorption characteristics of various resins [64, 65]; modeling of resins adsorption characteristics [66]; studies on the effect of saline solutions on the adsorption; and elution of ion species from various resins [67]. A new type of IEX resins (Macronet Hypersol MN100 and MN300) incorporating mixtures of tertiary and quaternary groups, linked onto a styrene–divinylbenzene macroporous hyperreticulated network or consisting of piperazine groups linked to a macroporous poly(styrene-co-divinyl-benzene) network have been synthesized and evaluated for Au(CN)2 − recovery from alkaline cyanide solutions. Preferable sorption of Au and Ag in comparison to base metals has been achieved [68, 69]. The influence of different parameters on the sorption profiles of trace and ultratraces of Au(I) species from the aqueous cyanide media onto the solid sorbents IEX polyurethane foams (PUFs) and commercial unloaded PUFsbased polyether type has been investigated. The synthesized IEX PUFs have been applied satisfactorily for complete retention and recovery of total inorganic gold(I) and/or gold(III) species spiked to tap and industrial wastewater samples. Chromatographic separation of Au(I) from Ag(I) and base metal ions (Fe, Ni, Cu, and Zn) using proposed sorbentpacked columns has been achieved [70]. Another group of N-containing anion exchange sorbents for Au, Pd, and Pt is represented by silica gel modified with ␥aminopropyltriethoxysilane [71] and rhodanine-bonded silica gel [72]. С18-silica gel modified with thioridazine hydrochloride [73] or pure С18-silica gel [74, 75] have also been evaluated. In these cases, analytical solutions have been treated with N-(1-carbaethoxypentadecyl)-trimethyl ammonium bromide in order to form ion association chloride complexes of Au, Pd, and Pt. Silica-based (Poly)Amine anion exchanges (containing monoamine, ethylenediamine, and diethylenetriamine functionalities) have shown high selectivity toward Pd and Pt and successfully applied for their recovery from precious metals refinery effluents [76]. A common matrix for SPE sorbents for Au, Pd, and Pt is represented by styrene polymers, e.g. containing diethylenetriamine functional groups [77] or ␣-pyridyl amine oligomer [78]. By optimizing the length of oligomers, the sorbent becomes more selective to Au(III) ions independently of the presence of other PGM ions in solution. Aminopolystyrene functionalized with azorhodanine, nitroxaminazo groups, or azoimidazole groups has also been applied [79]. The copolymer of styrene (in some cases chloromethylated [79]) with divinylbenzene is the most popular support for preparation of sorbents for Au, Pd, and Pt. It is functionalized with various reagents: (i) (ii) (iii) (iv) 1,3,4-Thiadiazole-2-amino-5-thiol [80] Dipicolinic acid [81] Polyhydroxamic acid [79, 82] 8-hydroxyquinoline [79, 83]  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim J. Sep. Sci. 2012, 35, 1249–1265 (v) Guanidine derivatives [79, 84] (vi) N,N′ -bis(2-hydroxybenzyl)-ethylenediamine [79, 85] (vii) Miscellaneous [79, 86]. A group of new functional sorbents on poly(vinylbenzyl chloride–acrylonitrile–divinylbenzene) matrix functionalized with aliphatic mono-, di-, and polyamines have been synthesized [87]. Recoveries over 95% were achieved for noble metals (Au(III), Pt(IV), Pd(II)) from multicomponent solutions. Sorbents on poly(vinylbenzyl chloride) support with immobilized aliphatic diamines and guanidine ligands have been proposed [88]. Vinyl alcohol could be part of the matrix of some Ncontaining anion exchangers, e.g. a copolymer of vinyl alcohol and acrylonitryl [89]. Sorbents have been synthesized by a single-step reaction between diethylenetriaminepentaacetic acid bisanhydride and polyvinyl alcohols with various molecular mass [90]. The polyacrylonitryl matrix could be functionalized with L-cysteine [91]. A sorbent containing amidoxime functional group is interesting for gold(III) enrichment, owing to its high capacity, fast sorption, and selectivity to Au(III). During the sorption process, the amidoxime groups are transformed to carboxylic, while Au(III) is reduced to Au(0); on subsequent sorbent ashing, spongy metallic gold is produced [92]. Gold(III) is known for being readily enriched from HCl solutions as [AuCl4 ]− by means of LLE in the presence of methyltrioctylammonium chloride (Aliquat 336). Sorbent based on naphthalene with linked Aliquat 336 has been proposed by Behpour et al. [93]. The sorption mechanism of Au(III) on methyltrioctylammonium chloride–naphthalene is given below: AuCl4− + R1 (R2 )3 N+ → [AuCl4− ][R1 (R2 )3 N+ ] (5) Aliquat 336 could be linked to poly(vinyl chloride), thus yielding membranes for enrichment of Au [94, 95] or Pd [96] as chloride complexes from HCl solutions. The extraction of these ions is fast and efficient, e.g. from industrial effluents or hydrometallurgical solutions. New publications on Au and PGM ions are regularly appearing [82, 89, 97–102]. Noble metals are most often sorbed as their chloride complexes and (rarer) as bromide complexes [97]. Most sorbents are selective to Au(III), Pd(II), and Pt(IV). In some cases, they cannot distinguish between oxidation states of platinum, Pt(II) and Pt(IV), when both are present in solution. Selective sorption of only Pt(II) has been reported [79, 89, 91, 101], hence under suitable conditions, the ions of Pt(II) and Pt(IV) [81] or Pt and Pd [84] could be selectively separated and enriched. 2.2 S-containing sorbents for preconcentration of Au, Pd, and Pt The ions of noble metals, including Au, Pd, Pt, are known for their stable complexes with reagents-containing sulfur www.jss-journal.com J. Sep. Sci. 2012, 35, 1249–1265 Sample Preparation 1255 Figure 1. Calix[4]pyrrole[2]thiophene immobilized on vinylbenzyl chloride/divinylbenzene copolymer [106]. donor atoms. This group of S-containing reagents is among the most successful sorbents for preconcentration of Au, Pd, and Pt from various complex matrices. Polyacryl supports and their derivatives are mostly employed for Au, Pd, and Pt. They are functionalized with various reagents and groups [4, 103] and the polymers by themselves could be modified for improving efficiency of sorption [104]. Efficient S-complexing resins are those containing macrocycles as functional groups, e.g. with linked thiamacrocycles T2 19C6 (1,4-dithia-19-crown-6) and T4 18C6 (1,4,7,10tetrathia-18-crown-6) [105]. Calix[4]pyrrole[2]thiophene immobilized on a cross-linked vinylbenzyl chloride/ divinylbenzene copolymer plays a role of a complex-forming ligand for the ions of Au, Pd, and Pt. The easily polarizable “soft” S atom in the molecule is selective toward the “soft” metal cations with suitable size (Fig. 1) [106]: С-18 silica gel could also be modified with pyrrolidine– carbodithioate reagent (PCDT) [107], mercaptopropyl groups [108], isodiphenylthiourea [109], and thiourea [110, 111]. The Amberlite sorbent brand is also represented in this class of S-containing complex-forming sorbents for Au, Pd, and Pt, viz. Amberlite XAD-4. The matrix of this resin is styrene–divinylbenzene copolymer [112]. It could be modified with bis(carboxymethyl)dithiocarbamate (CMDTC) [113]. The Duolite GT-73 resin with thiol functional groups is also based on styrene–divinylbenzene [114]. Part of the matrix could be chloromethylated polystyrene and the copolymer could be functionalized with S-bound dehydrodithizone [115]. S-containing sorbents working on anion exchange mechanism exhibit exceptionally broad diversity as matrices and functional groups. Sorbents based on modified silica gel are perhaps the best represented group. They are derivatized with thiourea [4] or thionalide [116]. Thionalide has been applied as functional group in the macroporous resin Bio-Beads SM-7 (acrylic ester polymer) [117]. The C-18 silica gel could also be impregnated with S-containing ligands [118]. In some cases, the sorbent is pure С-18 silica gel on which are retained the preformed Au(III) complexes [119]. In this procedure, ana C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim lytical solution is mixed with 1% aqueous ammonium salt of О,О-dithiophosphoric acid. The formed Au(III) complexes are then retained on the weakly polar sorbent and finally eluted with methanol. As a matrix in this kind of sorbents also could serve polymers based on divinylbenzene, vinylpyridine [120], chloromethylated styrene with immobilized dehydrodithizone [121], thioether [4], vinylthiopropionamide, as well as Dowex 128–200 [122]. The sorbent containing thiosemicarbazide on cross-linked polystyrene–divinylbenzene matrix is interesting in view of its stability in both acidic and alkaline media [123]. Sorbents on a polymetacrylic ester (Diaion) modified with dithizone have been reported [124], wherein the modifier is supposed to be linked to the matrix simultaneously by covalent bonds and adsorption forces. PUF enriched by thiocyanate has been applied for on-line sorption of platinum ions prior to ICP-OES determination with ultrasonic nebulization [125]. Linear aminopolystyrene matrix functionalized with azo-8-mercaptoquinoline has been applied for preconcentration of Au, Pd, and Pt [79]. A sulfur-containing chelating resin based on poly[4vinylbenzyl (2-hydroxyethyl) sulfide] has been proposed for Au(III) enrichment [126]. During sorption, the sulfide bond in the matrix is oxidized to sulfoxide and sulfone, while gold (III) is reduced to Au(0). Pyrrolydine dithiocarbamate has been applied for complexation and sorption of Pt(II) and Pt(IV) complexes on inner walls of a polytetrafluoroethylene knotted reactor (KR) in a flow injection ETAAS system [127]. A group of sorbents for Au, Pd, and Pt contains both N and S donor atoms in their functional centre. They show broad diversity of matrices and functional groups and the mechanisms of action have not been definitely established. A copolymer of vinyl alcohol and acrylonitryle with attached thioamide groups could enrich Pd(II) and Pt(II) from high-salt solutions [79]. A large group of S-containing sorbents is based on С18modified silica gel. The ligands N-alkyl- and N,N-dialkylN′ -acyl(aroyl)thioureas have been studied [128–132]. Good www.jss-journal.com 1256 E. Mladenova et al. selectivity for Pd(II) in the presence of concomitant ions of alkaline, alkaline earth, and other noble metals as well as Cu(II), Co(II), Fe(III), and Ni(II) has been obtained [129]. С16-silica gel can adsorb preformed dialkyldithiophosphate complexes of Pd(II) under softer conditions versus corresponding LLE [21]. Silica gel could also be functionalized with other reagents: amidinthiourea [133], 1,5bis(di-2-pyridyl)methylene thiocarbohydrazide [134], and 2mercaptobenzothiazole [135]. There are some other N- and S-containing sorbents for enrichment of Au, Pd, and Pt: (i) Copolymer of cellulose with acrylonitryle [79] (ii) Polyacrylonitryl fibers with incorporated aminothiourea [136], 2-mercaptobenzothiazole (POLYORGS XII) [29] (iii) Poly(dithiocarbamate) resin [137] (iv) Dithizone-functionalized chloromethylated poly (vinylpyridine) [138] (v) Cross-linked polystyrene support with bound N-methyl2-thioimidazol [139] or 2,5-dimercapto-1,3,4-thiodiazole [140] (vi) Polyacrylonitryle-2-amino-2-thiazoline resin [141] (vii) Polyacrylonitryle–thiosemicarbazide resin [142] J. Sep. Sci. 2012, 35, 1249–1265 Figure 2. Polystyrene-supported quaternary phosphonium chloride [146]. PVC matrix has been treated with di-2-ethylhexylphosphoric acid (D2EHPA). 2.5 Activated Carbon-based sorbents for preconcentration of Au, Pd, and Pt 2.4 P-containing sorbents for preconcentration of Au, Pd, and Pt AC are highly porous carbonaceous materials with unique properties as sorbents: well-developed microporous structure, large internal surface area, high degree of surface reactivity, and adsorption capacity. Applications of AC [56, 148–151] and single-walled carbon nanotubes [152] to preconcentration of trace Au, Pd, and Pt have been documented in the last decade. The kinetics of sorption of Au, Pd, and Pt on AC from UV-illuminated chloride solutions has been positively improved while the thermodynamic parameters (sorbent capacity, adsorption isotherm) have not been affected by UV irradiation [153]. Sorption on AC could follow three mechanisms: complex formation in the presence of complexing agent, reducing the oxidation state of the sorbate ion, and IEX on sorbent surface. Some authors suggest a combination of decreasing the oxidation state and surface sorption of the reduced products [154]. An addition O,O-diethyl ester of dithiophosphoric acid could serve as an example of precomplexation of analyte ions followed by sorption enrichment [155]. An interesting diversification of ACbased sorbents has been described [156], using chemically modified plant fibers (flax shive) by hot H2 SO4 . The ions of Au(III), Pd(II), and Pt(II) are retained on the surface, whereon they are reduced to metallic state, while the sorbent is oxidized thus creating new functional centers able to retain more ions. P-containing sorbents for SPE of Au, Pd, and Pt are still attracting research interest [145–147]. Example of a sorbent based on chloromethylated polystyrene with tris(2,6-dimethoxyphenyl)phosphine for selective enrichment of Au(III) and Pt(IV) as their chlorocomplexes is shown on Fig. 2. A sorbent based on polyvinylbenzyl chloride modified with diisobutyl phosphine sulfide for SPE of Au(III) and Pd(II) from solutions containing 10-fold excess of Cu(II), Ni(II), and Pb(II) ions has been proposed (Fig. 3). A similar sorbent in membrane forms for separation of Pd(II) from Cu(II) has been developed by Baba et al. [147]. The Figure 3. Polystyrene-supported diisobutylphosphine sulfide [145]. 2.3 O-containing sorbents for preconcentration of Au, Pd, and Pt There is a (limited) current interest in evaluating other SPE sorbents with donor atoms other than N and S. Sorbents with oxygen donor atoms provide such diversity. A sorbent based on morin-functionalized aminopropyl silica gel has been proposed [143]. Its positive assets are excellent stability in organic solvents, high enrichment factors, and low LODs for Au(III), Pd(II), and Pt(II). A group of sorbents with triisobutyl phosphine sulfide functional groups has been synthesized. They contain only О and/or О and S donor atoms [144] and exhibit either complex-forming or anion exchange mechanisms of action depending on the kind of their functional centre.  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com J. Sep. Sci. 2012, 35, 1249–1265 AC has been the preferred adsorbent for many years in the industrial precious metals recovery processes due to its high adsorption capacity, high adsorption rate, and good resistance to abrasion. Sorbents properties are governed by both the nature of the raw materials and the processes used to obtain the AC. That is way by which various types of source materials as well as different activation procedures including chemical modifications have been developed aiming to increase sorption capacity and selectivity [157]. Recently, it has been shown that in hydrochloric solutions, AC prepared by rice husk is highly selective for Au(III), and barley straw carbon is highly selective for Au(III) and other precious metals over various base metals [158]. ACs with different origins are the most widely used sorbents for Au recovery after cyanidation for sorption as Au (CN)2 − complex [159−162]. Sulfurimpregnated active carbon [163] or AC fibers [164] have also been used. Fundamental study performed for the adsorption of potassium gold cyanide from water onto industrial AC has shown that for very low equilibrium concentrations, gold is adsorbed as Au(CN)2 − anions and the adsorption has been found to be fully irreversible. For relatively concentrated solutions above a given surface coverage ratio, the adsorption of gold complexes becomes partly reversible, which indicates that, in this second stage, gold complexes are physically adsorbed [165]. The effect of the physical properties of an AC such as pore size distribution, specific surface, pore average diameter, on the gold adsorption from cyanide solution (Au (CN)2 − form), has been studied and it has been shown that the rate adsorption and the amount of adsorbed gold increased with the increase in macropores and with the increasing pore average diameter [166]. Criteria for choice of a brand of AC for hydrometallurgical recovery of gold from ore pulps in carbon-in-leaching and carbon-in-pulp processes have been elucidated [167]. ETAAS procedure for off-line preconcentration of Pd(II) on fullerene C60 with immobilized ammonium pyrrolidinedithiocarbamate (APDC) from environmental samples has been proposed [168]. The adsorbed complex is then quantitatively eluted but excessive amounts of Fe, Cu, Ni, and Pb are interfering. More selective ligands for modifying fullerene are called for. 2.6 Modified chitosan as a sorbent for preconcentration of Au, Pd, and Pt Chitosan, poly(␤-1,4-D-glucosamine), has become lately a popular matrix for preparation of sorbents for preconcentration of gold, palladium, and platinum ions. Owing to the presence of large number of nitrogen atoms in chitosan, various options for metal ion sorption by different mechanisms are provided (ion exchange, complex formation), depending on the kind of metal ion, pH, and other factors. Glutaraldehyde is most often applied as a cross-linking agent for chitosan-based sorbents, owing to the formation of imino bonds between amino groups of chitosan and aldehyde groups of glutaraldehyde. Palladium(II) from HCl media has been sorbed on glu C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Sample Preparation 1257 Figure 4. Structure of formed palladium complex with N-(2pyridylmethyl)chitosan [180]. taraldehyde cross-linked chitosan [169, 170]. Improved selectivity toward Pd(II) ions as well as better capacity of sorbents has been obtained by modification of glutaraldehyde crosslinked chitosan with S-containing reagents such as thiourea or dithiooxamide (rubeanic acid) [170–173]. Sorbent renders selective since both Pd and Pt ions are sorbed at the beginning of the enrichment process, while later on Pt(IV) ions are displaced in solution by Pd(II). The sorption capacity could be further improved by modifying of the cross-linked chitosan with polyethyleneamine [172]; sorption kinetics could be improved by the preparation of chitosan gel beads [174, 175] Ethylene glycol diglycidyl ether [176] as well as an agent containing quaternary N-atom [177] are also applied as cross-linking agents for chitosan. Suitable modifiers are glycine [178], L-lysine [179], 2-piridylmethanal [180], 2-thienylmethanal [180], and 3-(methylthio)propanal [180]. The structure of the formed palladium complex with N-(2pyridylmethyl)chitosan is given on Fig. 4. 2.7 Miscellaneous sorbents for enrichment of Au, Pd, and Pt Numerous sorbents with supports or functional groups not explicitely indicated are also widely employed [181–186]. For example, the polystyrene-based resin Amberlite XAD-16 extracts Pd(II) from alloys [183] and Pd and Au from Renay nickel and nickel oxide [184] by preconcentration as their iodide complexes. Chloride complexes of Au(III) have been extracted from geological materials and anode slime [182]. The Superlig 202 sorbent based on modified silica gel with molecular recognition ligand has been applied for performing the extraction of palladium, platinum, and rhodium in geochemical exploration techniques using electrothermal atomic absorption spectrometry [187]. The type of sorbent matrix has not always been reported [181, 185]. Less popular sorbents such as zeolites [1] (alumosilicates); biosorbents like bread yeast and green algae immobilized www.jss-journal.com 1258 E. Mladenova et al. J. Sep. Sci. 2012, 35, 1249–1265 Daniel et al. [207] have pioneered IIP applications to Pd in 2003. Most known IIP applications are based on 2hydroxyethyl methacrylate as a functional monomer, ethylene glycol dimethacrylate as a cross-linking agent, methanol, 2-methoxyethanol, or dimethyl sulfoxide as pore-forming agents, and 2,2’ -azobisisobutironitryle as initiator. Palladium(II) could be incorporated in the polymer in different manners: on silica gel [188]; sulfate-reducing bacteria [189]; desert willow Chilopsis linearis, being able to reduce Au(III) and accumulate Au(0) nanoparticles in plant [190]; dimethylaminemodified waste paper gel [191] have been reported. Although biosorption has been a proven technique for recovery of precious metals, its performance in real industrial effluents is still of concern [192] Nanoparticles of TiO2 have also been applied as sorbent for Au and Pd [193]. SPE on activated Al2 O3 has been applied for enrichment of Pd from urban wastewater [194] and Pt from water [8, 195, 196]. Cation exchange resins have been applied for platinum group metals in strongly acidic media. Resins based on sulfonic acid, phosphoric acid, aminocarboxylic acids, amidoxime, CuS, silica gel impregnated with Cu2 [Fe(CN)6 ] or Ni2 [Fe(CN)6 ] [56], cellulose phosphate (Cellex-P) containing –О-PO(OH)2 functional groups [197] have been reported. The strong acidic cation exchange resin Type 732 has been applied to sorb common concomitant ions of Na+ , K+ , Ca2+ , Mg2+ , Fe3+ , and Al3+ from HCl medium, while the chloride complexes of target ions of Au, Pd, and Pt pass through the column in a clever flow injection on-line clean-up ETAAS procedure [198]. Total recovery of Au(III) from industrial solutions (hydrochloric medium) has been achieved by using selective sorption on cross-linked lignophenol [199]. By immobilization of amines onto cross-linked lignophenol, selective adsorption of all Au(III), Pd(II), and Pt(IV) from industrial solutions could be ensured [200–204]. (i) Ternary ion associate complex between Pd2+ , I− , or SCN− , and N-acetyl-4-vinylpyridine [206] – in this case, the formed complex, [PdI4 ]2− or [Pd(SCN)4 ]2− , is extracted; (ii) ternary complex of Pd2+ , 8-aminoquinoline, and 4vinylpyridine [208]; (iii) ternary complex of Pd2+ , dimethylglyoxime (DMG), and 4-vinylpyridine [207]; (iv) ternary complex of Pd2+ , 8-aminoquinoline, 8hydroxyquinoline, or 8-mercaptoquinoline as a first ligand and 4-vinylpyridine as a second ligand [209]. 2.8 Ion-imprinted polymers as sorbents for Pd preconcentration 3 Analytical conditions for preconcentration of Au, Pd, and Pt Palladium(II) enrichment by means of IIPs is mostly addressed as compared with other noble metals, owing to good complex-forming properties of this analyte and its importance as emerging toxic micropollutant. IIPs are highly selective and intensively studied as SPE sorbents as seen in recent review [205]. In brief, IIPs is synthesized in the presence of the Pd2+ ion and then the ion is washed from the sorbent by means of a suitable reagent (often HCl), leaving an imprint of the ion – a cavity with a suitable size and orientation – which is able to accommodate a Pd2+ ion in a following enrichment step. The target ion could be bound to the sorbent chain by means of noncovalent interactions (hydrogen bonds, ion bonds, hydrophobic interactions, Van der Waals interactions) or by covalent bonding. Four different approaches for synthesis of IIPs for metal ions could be distinguished [206]: (i) Cross-linking of linear polymers containing metal groups in their structures with bifunctional reagents in the presence of metal ions; (ii) synthesis and isolation of binary complexes of metal ions and ligands containing vinyl groups with subsequent polymerization with matrix-forming monomers; (iii) surface imprinting on the aqueous–organic interface; (iv) binary/ternary mixed ligand complexes of metal ions with nonvinyl chelate and vinyl ligand.  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A simplified example of Pd(II) ion imprinting is presented on Fig. 5. Some authors have employed amine-functionalized silica gel as a matrix for Pd(II) imprinting [210]. GodlewskaŻyłkiewicz et al. have synthesized new IIP materials using Pd(II) chelate complexes with APDC, N,N’-diethylthiourea, and DMG [211]. Noble metals have been determined in a broad variety of sample matrices (geological, industrial, environmental, biological, etc.) Useful examples from recent literature for Au, Pd, and Pt determination after separation and preconcentration by SPE are given in Table 3. Direct analysis of solid samples could hardly yield reliable results at sub-ppm concentrations because of lack of sensitivity and matrix effects. Solid samples are brought in solution by wet decomposition and much rarer by dry ashing of biological/organic materials or high temperature fusion, depending of kind of matrix, analyte concentration, and subsequent treatment. Alkaline fusion provides high-salt melts for most geological materials [12,110]. Dry ashing with dissolution of ashes in acid(s) has been applied to biological, botanical, clinical, and pharmaceutical samples [104], as well as to some environmental materials [104, 124, 148]. Most common and well established are wet digestion procedures either in open vessels or closed pressurized systems under microwave heating [5, 30, 97, 124, 168, 212]. Microwave-assisted decompositions proved fast and efficient for matrices with high organic content such as biological, pharmaceutical, and other materials [13, 53, 54, 77, 119, 134]. Chlorination by means of boiling aqua regia, often under reflux conditions, has been widely applied for bringing noble metals in soluble chloride complexes [2, 154, 181, 187]. www.jss-journal.com J. Sep. Sci. 2012, 35, 1249–1265 Sample Preparation 1259 Figure 5. Scheme for the synthesis of Pd(II) IIP [206]. Composite eluents containing complex-forming additives such as thiourea by itself or in dilute HCl, HNO3 , or HClO4 , and organic solvents CH3 OH or C2 H5 OH have also been employed for better efficiency or kinetics of elution. Miscellaneous other additives are known as well: aqueous ammonia, KI solution in methanol [182], N,N-dimethylformamide [93], etc. In rare cases, sorbent may need decomposition by wet digestion [154] or microwave-assisted decomposition [13] with dissolution in appropriate reagent for instrumental quantification. The complex-forming agent may be completely or partly eluted by eluents as methanol [127] or ethanol [5]. Important considerations in these procedures are the choice of SPE sorbent and the mode of sorption (static or dynamic), depending on sample matrix and sample mass, the volume of eluate, total dissolved solid content, and other considerations: selectivity, availability and price of sorbent, sensitivity of instrumental method, possibility for direct analysis of efluate without further treatments. Scaling down analytical procedures in flow and flow injection mode and possibility for automation and increasing sample throughput rates are additional technical considerations. Careful optimization of several chemical and instrumental parameters is essential: concentration of acid(s), temperature, contact time, flow rates for sorption and elution. 3.1 Instrumental techniques for quantification of Au, Pd, and Pt AAS with flame and electrothermal atomization (FAAS, ETAAS, or GFAAS) are widely used routine techniques [212, 213]. ETAAS is preferred for better sensitivity by 2−3 orders of magnitude [9, 11, 56]. The LODs and economic characteristics of ETAAS are competitive to those of ICP-MS. The single-element mode and limited linear range are distinct disadvantages of ETAAS. Occasional cross C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim contamination and memory effects could be expected because of the widespread use of noble metals as chemical modifiers in ETAAS. Background correction, acid/solventmatched calibration matrix, and careful optimization of temperature program are essentials. Structured background from 500-fold excess of Fe could be expected at Au 242.8nm line. Large excess of HCl, HNO3 , and H2 SO4 (>1– 2 mol L−1 ) could be depressive and corrosive to graphite surfaces. Excessive background from KSCN-containing eluents has been documented, while glycine and thiourea are tolerated [9]. The multielement ICP-OES technique provides instrumental LODs down to a few ␮g L−1 for Au and Pd and between 10 and 50 ␮g L−1 for Pt. Advantages of ICP-OES are multielement capabilities, good precision, established methodology, and well-documented spectral interferences [214−216]. ICP-OES procedures with preconcentration of Au, Pd, and Pt have been applied down noble metal concentrations of 10−4 –10−6 %. Sub-␮g L−1 instrumental LODs for Au, Pd, and Pt are achieved by ICP-MS [217]. Potential spectral interferences due to direct spectral overlaps and molecular ions with close m/z ratios for 102 Pd+ , 104 Pd+ , 105 Pd+ , 106 Pd+ , 108 Pd+ , and 110 Pd+ and 190 Pt+ , 192 Pt+ , 194 Pt+ , 195 Pt+ , 196 Pt+ , 196 + Pt , and 198 Pt+ isotopes have been thoroughly reviewed by Bencs et al. [218]. Some examples of m/z overlaps are 106 Pd by 40 Ar65 Cu1 H+ , 87 Rb18 O1 H+ [218], 106 Cd+ , 40 Ar66 Zn+ , 90 Zr16 O+ . The alternative isotope 105 Pd with similar abundance has been utilized in analyses of street dust because of negligible degree of interferences from Ar and oxides of Zn, Zr, and Mo, although yttrium as 89 Y16 O+ affects 105 Pd signal. Somewhat higher power settings (1350 W) could have been applied to reduce the effect by YO+ , ArCu+ , and ArGa+ on 105 Pd quantification. The effect of organic solvents could be reduced by flowinjection mode of elution and sampling of small amount of methanol extract, e.g. only 140 ␮L CH3 OH [119]. www.jss-journal.com 1260 J. Sep. Sci. 2012, 35, 1249–1265 E. Mladenova et al. Table 3. Instrumental techniques for the determination of Au, Pd, and Pt in real samples Sample Analyte Eluent composition Technique References Environmental samples Pd Au Pt Au Au, Pd, Pt Pt Pd, Pt Pt(IV) Pd Pd, Pt Pd, Pt Pd Pd Pt(IV) Pd, Pt Pd Pd, Pt Pt Pd, Pt Pt Pd Au, Pd, Pt Au, Pd, Pt Au, Pd Au Au, Pd, Pt Pd, Pt Au, Pd, Pt Pt Pd Pt Au Au, Pd, Pt Pd, Pt Pd, Pt Pd, Pt 4 mol L−1 HNO3 N,N-dimethylformamide 10% HNO3 0.5% KCN CHCl3 2 mol L−1 HNO3 2 mol L−1 (NH2 )2 CS 2 mol L−1 NH4 OH KCN 0.3 mol L−1 (NH2 )2 CS in 1 mol L−1 HCl 0.1 mol L−1 (NH2 )2 CS in 1 mol L−1 HCl 1 mol L−1 M (NH2 )2 CS in CH3 COOCH3 C2 H5 OH 2 mol L−1 NH4 OH 4 mol L−1 HNO3 C2 H5 OH (NH2 )2 CS in HNO3 2 mol L−1 HNO3 0.3 mol L−1 (NH2 )2 CS in 1 mol L−1 HCl 2 mol L−1 HNO3 4 mol L−1 HNO3 (NH2 )2 CS 1 mol L−1 HCl Conc. HNO3 + conc. HClO4 0.3 mol L−1 KI in CH3 OH Conc. HCl + conc. HNO3 + H2 O2 2 mol L−1 (NH2 )2 CS (NH2 )2 CS 2% (NH2 )2 CS 1 mol L−1 (NH2 )2 CS in CH3 COCH3 2% (NH2 )2 CS 0.3 mol L−1 KI in CH3 OH Conc. HCl + conc. HNO3 + H2 O2 1 mol L−1 HCl in C2 H5 OH 1 mol L−1 HCl in C2 H5 OH 5 mol L−1 NH4 OH + 1.2% CMDTC 0.5 mol L−1 NH4 OH + 1.2% CMDTC CH3 OH C2 H5 OH CH3 OH IDMS FAAS ICP-OES FAAS NAA ETAAS ETAAS ICPMS ICPMS ETAAS ICPMS FAAS, ETAAS ETAAS ICPMS ICPMS ETAAS ETAAS ETAAS ETAAS ETAAS IDMS FAAS NAA, ICPMS FAAS FAAS ICPMS ETAAS FAAS FAAS FAAS, ETAAS FAAS FAAS ICPMS FAAS FAAS ETAAS ICP-AES ETAAS HPLC ICPMS [53] [93] [125] [82] [107] [134] [187] [195] [194] [9] [5] [18] [168] [195] [54] [212] [125] [134] [9] [134] [53] [109] [181] [154] [182] [13] [187] [109] [110] [18] [110] [182] [13] [57] [57] [113] [113] [127] [129] [119] Nature waters Urban waters Urban dust Urban air Soil Grass Geological samples Silicates Sediments Metallurgical samples Anode slime Ores Alloys Biological samples Blood Urine Pt(II), Pd(IV) Pd Au Isotope dilution (ID) has been applied for better precision in ICPMS procedures [51, 55]. For platinum, the interference on 195 Pt by 179 Hf16 O+ , due to small m/z difference (0.021944 Da) has been successfully resolved at 8885 m/⌬m [218] and medium input power (1350 W). Representative instrumental limits of detection (ILODs) for Au, Pd, and Pt in final solutions of concentrates or column eluates by relevant analytical techniques are as follows: 10−50 ␮g L−1 Au and Pd, 50−100 ␮g L−1 Pt by FAAS; 10 pg Au, 5−25 pg Pd, 50−200 pg Pt by ETAAS; 1−10 ␮g L−1 Au and Pd, 10−50 ␮g L−1 Pt by ICP-OES; <1 ng L−1 Au, Pd and Pt by ICPMS; 1−10 pg Au, 0.1−1 ng Pd, 1−10 ng Pt by NAA.  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 4 Concluding remarks Efficient preconcentration of nanotrace and picotrace amounts of Au, Pd, and Pt from complex matrices is essential for obtaining accurate and precise analytical results. Enrichment by sorption plays an important role in analytical practice. Large variety of SPE sorbents is available for Au(III), Pd(II), Pt(II), and Pt(IV) ions. The synthesized resins are based on different matrices and ligands, with complex formation or ion exchange, with covalent or electrostatically bound functional groups, in various physical forms as granules, fibres, powders, cellulose filters, etc. Commercially available SPE sorbents (Amberlite, Duolite, Purolit, Dowex, POLYORGS) are used directly or after further treatments. Dynamic www.jss-journal.com J. Sep. Sci. 2012, 35, 1249–1265 sorption is the preferred mode. Recent applications to geological, industrial, pharmaceutical, biological, and other materials are tabulated and extensively referenced. The authors have declared no conflict of interest. 5 References [1] Myasoedova, G. V., Mokhodoeva, O. B., Kubrakova, I. V., Anal. Sci. 2007, 23, 1031–1039. Sample Preparation 1261 [25] Chang, X., Su, Q., Liang, D., Wei, X., Wang, B., Talanta 2002, 57, 253–261. [26] Gholivand, M. B., Garrosi, E., Khorsandipoor, S., Anal. Lett. 2000, 33, 1645–1654. [27] Jermakowicz-Bartkowiak, D., React. Funct. Polym. 2007, 67, 1505–1514. [28] Su, Z-X., Pu, Q.-S., Luo, X.-Y., Chang, X.-J., Zhan, G.-Y., Ren, F.-Z., Talanta 1995, 42, 1127–1133. [29] Myasoedova, G. V., Fresenius J. Anal. Chem. 1991, 341, 586–591. [2] Barefoot, R. R., Van Loon, J. C., Talanta 1999, 49, 1–14. [30] Kubrakova, I., Spectrochim. Acta, Part B 1997, 52, 1469– 1481. [3] Godlewska-Żyłkiewicz, B., Microchim. Acta 2004, 147, 189–210. [31] Myasoedova, G. V., Antokol′ skaya, I. I., Savvin, S. B., Talanta 1985, 32, 1105–1112. [4] Bilba, D., Bejan, D., Tofan, L., Croat. Chem. Acta 1998, 71, 155–178. [32] Antokol′ skaya, I. I., Myasoedova, G. V., Bol′ shakova, L. I., Ezernitskaya, M. G., Volynets, M. P., Karyakin, A. V., Savvin, S. B., Zh. Anal. Khim. 1976, 31, 742–745. [5] Leśniewska, B. A., Godlewska-Żyłkiewicz, B., Ruszczyńska, A., Bulska, E., Hulanicki, A., Anal. Chim. Acta 2006, 564, 236–242. [6] Godlewska-Żyłkiewicz, B., Leśniewska, B., Gasiewska, ˛ U., Hulanicki, A., Anal. Lett. 2000, 33, 2805–2820. [7] Brajter, K., Słonawska, K., Microchim. Acta 1989, 97, 137–143. [8] Godlewska-Żyłkiewicz, B., Leśniewska, B., Michałowski, J., Hulanicki, A., Int. J. Environ. Anal. Chem. 1999, 75, 71–81. [9] Dziwulska, U., Bajguz, A., Godlewska-Żyłkiewicz, B., Anal. Lett. 2004, 37, 2189–2203. [10] Lásztity, A., Kelkó-Lévai, Á., Zih-Perényi, K., Varga, I., Talanta 2003, 59, 393–398. [11] Basargin, N. N., Zueva, M. V., Rozovskii, Yu. G., Pashchenko, K. P., J. Anal. Chem. 2005, 60, 234–239. [12] Muzikar, M., Fontàs, C., Hidalgo, M., Havel, J., Salvadó, V., Talanta 2006, 70, 1081–1086. [13] Coedo, A. G., Dorado, M. T., Padilla, I., Alguacil, F., Anal. Chim. Acta 1997, 340, 31–40. [33] Myasoedova, G. V., Antokol′ skaya, I. I., Bol′ shakova, L. I., Danilova, F. I., Fedotova, I. A., Varshal, E. B., Rakovskii, E. E., Savvin, S. B., Zh. Anal. Khim. 1982, 37, 1837–1840. [34] Myasoedova, G. V., Antokol′ skaya, I. I., Danilova, F. I., Fedotova, I. A., Grin′ kov, V. P., Ustinova, N. V., Naumenko, E. A., Danilova, E. Y., Savvin, S. B., Zh. Anal. Khim. 1982, 37, 1578–1583. [35] Myasoedova, G. V., Antokol′ skaya, I. I., Dmitrieva, G. A., Kubarev, S. V., Moiseeva, G. A., Danilova, F. I., Grishina, O. N., Zhukova, N. S., Savvin, S. B., Zh. Anal. Khim. 1988, 43, 673–676. [36] Myasoedova, G. V., Antokol′ skaya, I. I., Kubrakova, I. V., Belova, E. V., Mezhirov, M. S., Varshal, E. B., Grishina, O. N., Zhukova, N. G., Danilova, F. I., Savvin, S. B., Zh. Anal. Khim. 1986, 41, 1816–1820. [37] Shvoeva, O. P., Kuchava, G. P., Myasoedova, G. V., Savvin, S. B., Bannykh, L. N., Zhukova, N. G., Grishina, O. N., Mezhirov, M. S., Zh. Anal. Khim. 1985, 40, 1606– 1610. [14] Pohl, P., Prusisz, B., Zyrnicki, W., Talanta 2005, 67, 155– 161. [38] Shcherbinina, N. I., Ishmiyarova, G. R., Kahoves, J., Švec, F., Bol′ shakova, L. I., Myasoedova, G. V., Savvin, S. B., Zh. Anal. Khim. 1989, 44, 615–619. [15] Iglesias, M., Anticó, E., Salvadó, V., Talanta 2003, 59, 651–657. [39] Myasoedova, G. V., Zh. Anal. Khim. 1990, 45, 1878– 1887. [16] Hoshi, S., Higashihara, K., Suzuki, M., Sakurada, Y., Sugawara, K., Uto, M., Akatsuka, K., Talanta 1997, 44, 571–576. [40] Blokhin, A. A., Abovskii, N. D., Murashkin, Y. V., Russ. J. Appl. Chem. 2007, 80, 1058–1062. [17] Elci, L., Anal. Lett. 1993, 26, 1025–1036. [41] Hubicki, Z., Leszczyńska, M., Desalination 2005, 175, 227–236. [18] Tokalıoğlu, Ş., Oymak, T., Kartal, Ş., Anal. Chim. Acta 2004, 511, 255–260. [42] Hubicki, Z., Wójcik, G., J. Hazard. Mater. 2006, 136, 770– 775. [19] Otruba, V., Strnadová, M., Skalnı́ková, B., Talanta 1993, 40, 221–224. [43] Matsubara, I., Takeda, Y., Ishida, K., Anal. Sci. 2003, 19, 1427–1429. [20] Komendova-Vlasenkova, R., Sommer, L., Coll. Czech. Chem. Commun. 2002, 67, 454–470. [44] Matsubara, I., Takeda, Y., Ishida, K., Fresenius J. Anal. Chem. 2000, 366, 213–217. [21] Spivakov, B. Y., Malofeeva, G. I., Petrukhin, O. M., Anal. Sci. 2006, 22, 503–519. [45] Hubicki, Z., Wójcik, G., Adsorpt. Sci. Technol. 2004, 22, 627–637. [22] Chang, X., Su, Z., Yang, D., Gong, B., Pu, Q., Li, S.-K., Anal. Chim. Acta 1997, 354, 143–149. [23] Yang, D., Chang, X. J., Liu, Y. W., Wang, S., Microchim. Acta 2004, 147, 219–223. [24] Gong, B., Talanta 2002, 57, 89–95.  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [46] Gaita, R., Al-Bazi, S. J., Talanta 1995, 42, 249–255. [47] Hubicki, Z., Leszczyńska, M., Łodyga, B., Łodyga, A., Miner. Eng. 2006, 19, 1341–1347. [48] Lee, S. H., Chung, H., Sep. Sci.Technol. 2003, 38, 3459– 3472. www.jss-journal.com 1262 E. Mladenova et al. J. Sep. Sci. 2012, 35, 1249–1265 [49] Kovacheva, P., Djingova, R., Anal. Chim. Acta 2002, 464, 7–13. I. A., Tsysin, G. I., Zolotov, Y. A., Anal. Chim. Acta 1996, 334, 167–175. [50] Jarvis, I., Totland, M. M., Jarvis, K. E., Analyst 1997, 122, 19–26. [78] Kagaya, S., Kodajima, D., Takahashi, Y., Kanbara, T., Hasegawa, K., J. Mater. Chem. 2000, 10, 2442–2444. [51] Pearson, D. G., Woodland, S. J., Chem. Geol. 2000, 165, 87–107. [79] Myasoedova, G. V., Savvin, S. B., Crit. Rev. Anal. Chem. 1986, 17, 1–63. [52] Brzezicka, M., Baranowska, I., Spectrochim. Acta, Part B 2001, 56, 2513–2520. [80] Leung, B. K.-O., Hudson, M. J., Solvent Extr. Ion Exch. 1992, 10, 173–190. [53] Hann, S., Koellensperger, G., Kanitsar, K., Stingeder, G., J. Anal. At. Spectrom. 2001, 16, 1057–1063. [81] Chessa, G., Marangoni, G., Pitteri, B., Stevanato, N., Vavasori, A., React. Polym. 1991, 14, 143–150. [54] Kanitsar, K., Koellensperger, G., Hann, S., Limbeck, A., Puxbaum, H., Stingeder, G., J. Anal. At. Spectrom. 2003, 18, 239–246. [82] Vernon, F., Zin, W. Md., Anal. Chim. Acta 1981, 123, 309–313. [55] Müller, M., Heumann, K. G., Fresenius J. Anal. Chem. 2000, 368, 109–115. [56] Kolarik, Z., Renard, E. V., Platinum Met. Rev. 2003, 47, 74–87. [57] Kovalev, I. A., Bogacheva, L. V., Tsysin, G. I., Formanovsky, A. A., Zolotov, Y. A., Talanta 2000, 52, 39–50. [58] Brajter, K., Slonawska, K., Fresenius J. Anal. Chem. 1986, 323, 145–147. [83] Myasoedova, G. V., Antokol’skaya, I. I., Savvin, S. B., Talanta 1985, 32, 1105–1112. [84] Gulko, A., Feigenbaum, H., Schmuckler, G., Anal. Chim. Acta 1972, 59, 397–402. [85] Djamali, M. G., Lieser, K. H., Angew. Makromol. Chem. 1983, 113, 129–140. [86] Nadkarni, R. A., Morrison, G. H., Anal. Chem. 1974, 46, 232–236. [59] Brajter, K., Slonawska, K., Anal. Lett. 1988, 21, 311–318. [87] Jermakowicz-Bartkowiak, D., Kolarz, B. N., Serwin, A., React. Funct. Polym. 2005, 65, 135–142. [60] Kononova, O. N., Kholmogorov, A. G., Mikhlina, E. V., Hydrometallurgy 1998, 48, 65–72. [88] Jermakowicz-Bartkowiak, D., React. Funct. Polym. 2005, 62, 115–128. [61] Gaita, R., Al-Bazi, S. J., Talanta 1995, 42, 249–255. [89] Beauvaris, R. A., Alexandratos, S. D., React. Funct. Polym. 1998, 36, 113–123. [62] Cortina, J., Menhardt, E., Roijals, O., Marti, V., React. Funct. Polym. 1998, 36, 149–165. [63] Els, E., Lorenzen, L., Aldrich, C., Miner. Eng. 2000, 13, 401–414. [64] Leao, V. A., Lukey, G. C., Van Deventer, J. S. J., Ciminelli, V. S. T., Solvent Extr. Ion Exch. 2001, 19, 507–530. [65] Cortina, J. L., Meinhardt, E., Roijals, O., Martı́, V., React. Funct. Polym. 1998, 36, 149–165. [66] Lukey, G. C., Van Deventer, J. S. J., Shallcross, D. C., Miner. Eng. 2000, 13, 1243–1261. [90] Montembault, V., Soutif, J.-C., Brosse, J.-C., Grote, M., React. Funct. Polym. 1999, 39, 253–261. [91] Liu, C.-Y., Sun, P.-Y., Anal. Chim. Acta 1981, 132, 187– 193. [92] Weiping, L., Ruowen, F., Yun, L., Hanmin, Z., React. Polym. 1994, 22, 1–8. [93] Behpour, M., Attaran, A. M., Ghoreishi, S. M., Soltani, N., Anal. Bioanal. Chem. 2005, 382, 444–447. [67] Lukey, G. C., Van Deventer, J. S. J., Shallcross, D. C., Hydrometallurgy 2000, 56, 217–236. [94] Argiropoulos, G., Cattrall, R. W., Hamilton, I. C., Kolev, S. D., Paimin, R., J. Membr. Sci. 1998, 138, 279– 285. [68] Cortina, J. L., Kautzmann, R. M., Gliese, R., Sampaio, C. H., React. Funct. Polym. 2004, 60, 97–107. [95] Kolev, S. D., Argiropoulos, G., Cattrall, R. W., Hamilton, I. C., Paimin, R., J. Membr. Sci. 1997, 137, 261–269. [69] Warshawsky, A., Kahana, N., Kampel, V., Rogachev, I., Kautzmann, R. M., Cortina, J. L., Sampaio, C. H., Macromol. Mater. Eng. 2001, 286, 285–295. [96] Kolev, S. D., Sakai, Y., Cattrall, R. W., Paimin, R., Potter, I. D., Anal. Chim. Acta 2000, 413, 241–246. [70] Faraga, A. B., Solimana, M. H., Abdel-Rasoula, O. S., El-Shahawi, M. S., Anal. Chim. Acta 2007, 601, 218– 229. [97] Makishima, A., Nakanishi, M., Nakamura, E., Anal. Chem. 2001, 73, 5240–5246. [98] Hidalgo, M., Uheida, A., Salvadó, V., Fontàs, C., Solvent Extr. Ion Exch. 2006, 24, 931–942. [71] Tong, A., Akama, Y., Tanaka, S., Anal. Chim. Acta 1990, 230, 179–181. [99] Lee, J. S., Tavlarides, L. L., Solvent Extr. Ion Exch. 2002, 20, 407–427. [72] Liu, P., Pu, Q.-S., Sun, Q.-Y., Su, Z.-X., Fresenius J. Anal. Chem. 2000, 366, 816–820. [100] Chen, Y.-Y., Yuan, X.-Z., React. Polym. 1994, 23, 165– 172. [73] Farhadi, K., Teimouri, G., Talanta 2005, 65, 925–929. [101] Talanova, G. G., Zhong, L., Kravchenko, O. V., Yatsimirskii, K. B., Bartsch, R. A., J. Appl. Polym. Sci. 2001, 80, 207–213. [74] Vlašánkova, R., Otruba, V., Bendl, J., Fišera, M., Kanický, V., Talanta 1999, 48, 839–846. [75] Kanický, V., Otruba, V., Mermet, J.-M., Talanta 1999, 48, 859–866. [76] Kramer, J., Driessen, J., Koch, K., Reedijk, J., Sep. Sci. Technol. 2004, 39, 63–75. [77] Kubrakova, I. V., Kudinova, T. F., Kuźmin, N. M., Kovalev,  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [102] Di, P., Davey, D. E., Talanta 1995, 42, 685–692. [103] Chang, X., Su, Z., Zhan, G., Luo, X., Gao, W., Analyst 1994, 119, 1445–1449. [104] Medved, J., Bujdoš, M., Matúš, P., Kubová, J., Anal. Bioanal. Chem. 2004, 379, 60–65. www.jss-journal.com J. Sep. Sci. 2012, 35, 1249–1265 [105] Bruening, R. L., Tarbet, B. J., Krakowiak, K. E., Bruening, M. L., Izatt, R. M., Bradshaw, J. S., Anal. Chem. 1991, 63, 1014–1017. [106] Kałedkowski, A., Trochimczuk, A. W., React. Funct. ˛ Polym. 2006, 66, 957–966. [107] Shah, N. K., Wai, C. M., J. Radioanal. Nucl. Chem. 1989, 130, 451–459. Sample Preparation 1263 [134] Ojeda, C. B., Rojas, F. S., Pavón, J. M. C., Garcı́a de Torres, A., Anal. Chim. Acta 2003, 494, 97–103. [135] Pu, G., Su, Z., Hu, Z., Chang, X., Yang, M., J. Anal. At. Spectrom. 1998, 13, 249–253. [136] Gong, B., Wang, Y., Anal. Bioanal. Chem. 2002, 372, 597–600. [137] Chung, Y. S., Barnes, R. M., J. Anal. At. Spectrom. 1988, 3, 1079–1082. [108] Losev, V. N., Kudrina, Y. V., Maznyak, N. V., Trofimchuk, A. K., J. Anal. Chem. 2003, 58, 124–128. [138] Shah, R., Devi, S., Anal. Chim. Acta 1997, 341, 217–224. [109] Liu, P., Su, Z., Wu, X., Pu, Q., J. Anal. At. Spectrom. 2002, 17, 125–130. [139] Chen, Y.-Y., Cai, G.-P., Wang, N.-D., J. Macromol. Sci. Part A Pure Appl. Chem. 1990, 27, 1321–1333. [110] Liu, P., Pu, Q., Hu, Z., Su, Z., Analyst 2000, 125, 1205– 1209. [140] Qu, R., Sun, C., Ji, C., Wang, C., Xu, Q., Lu, S., Li, C., Xu, G., Cheng, G., J. Appl. Polym. Sci. 2006, 101, 631–637. [111] Liu, P., Pu, Q., Su, Z., Analyst 2000, 125, 147–150. [141] Chen, Y., Zhao, Y., React. Funct. Polym. 2003, 55, 89–98. [112] Parent, M., Vanhoe, H., Moens, L., Dams, R., Fresenius J. Anal. Chem. 1996, 354, 664–667. [142] Chen, Y.-Y., Liang, C., Chao, Y., React. Funct. Polym. 1998, 36, 51–58. [113] Lee, M. L., Tölg, G., Beinrohr, E., Tschöpel, P., Anal. Chim. Acta 1993, 272, 193–203. [143] Hassanien, M. M., Abou-El-Sherbini, K. S., Talanta 2006, 68, 1550–1559. [114] Pohl, P., Prusisz, B., Microchim. Acta 2005, 150, 159–165. [144] Sánchez, J. M., Hidalgo, M., Salvadó, V., Solvent Extr. Ion Exch. 2004, 22, 285–303. [115] Grote, M., Sandrock, M., Kettrup, A., React. Polym. 1990, 13, 267–290. [116] Terada, K., Matsumoto, K., Taniguchi, Y., Anal. Chim. Acta 1983, 147, 411–415. [145] Congost, M. A., Salvatierra, D., Marquès, G., Bourdelande, J. L., Font, J., Valiente, M., React. Funct. Polym. 1996, 28, 191–200. [117] Chwastowska, J., Żmijewska, W., Sterlı́nska, E., Anal. Chim. Acta 1993, 276, 265–270. [146] Fujiwara, M., Matsushita, T., Kobayashi, T., Yamashoji, Y., Tanaka, M., Anal. Chim. Acta 1993, 274, 293–297. [118] Praveen, R. S., Daniel, S., Rao, T. P., Anal. Lett. 2006, 39, 1187–1199. [147] Baba, Y., Hoaki, K., Perera, J. M., Stevens, G. W., Cardwell, T. J., Cattrall, R. W., Kolev, S. D., Compt. Rend. Acad. Bulg. Sci. 2001, 54, 69–72. [119] Dressler, V. L., Pozebon, D., Curtius, A. J., Anal. Chim. Acta 2001, 438, 235–244. [120] Antopov, N. I., Dragavtseva, N. A., Skobeleva, V. I., Matveeva, N. I., Tsvetnye Metally 1975, 9, 80–82. [121] Grote, M., Kettrup, A., Anal. Chim. Acta 1985, 172, 223– 239. [148] Jankowski, K., Jackowska, A., Łukasiak, P., Anal. Chim. Acta 2005, 540, 197–205. [149] Tarkovskaya, I. A., Kulik, N. V., Rosokha, S. V., Tikhonova, L. P., Svarkovskaya, I. P., Ukr. Khim. Zh. 2002, 68, 79–83. [150] Lin, S., Zheng, C., Yun, G., Talanta 1995, 42, 921–926. [122] Garcı́a, M. M. G., Rojas, F. S., Ojeda, C. B., Garcı́a de Torres, A., Pavón, J. M. C., Anal. Bioanal. Chem. 2003, 375, 1229–1233. [151] Gentscheva, G., Vassileva, P., Tzvetkova, P., Lakov, L., Peshev, O., Ivanova, E., J. Porous Mater. 2008, 15, 331– 334. [123] Siddhanta, S., Das, H. R., Talanta 1985, 32, 457–460. [152] Cheng, X., Chen, S., Wang, X., Liu, C., At. Spectrosc. 2010, 31, 75–80. [124] Chwastowska, J., Skwara, W., Sterlińska, E., Pszonicki, L., Talanta 2004, 64, 224–229. [125] Cerutti, S., Salonia, J. A., Ferreira, S. L. C., Olsina, R. A., Martinez, L. D., Talanta 2004, 63, 1077–1082. [153] Ageeva, L. D., Kolpakova, N. A., Kovyrkina, T. V., Potsyapun, N. P., Buinovskii, A. S., J. Anal. Chem. 2001, 56, 137–139. [126] Qu, R., Sun, C., Ji, C., Xu, Q., Wang, C., Cheng, G., Eur. Polym. J. 2006, 42, 254–258. [154] Chakrapani, G., Mahanta, P. L., Murty, D. S. R., Gomathy, B., Talanta 2001, 53, 1139–1147. [127] Ivanova, E., Adams, F., Fresenius J. Anal. Chem. 1998, 361, 445–450. [155] Soylak, M., Elci, L., Dogan, M., Anal. Lett. 2000, 33, 513– 525. [128] Limbeck, A., Rendl, J., Puxbaum, H., J. Anal. At. Spectrom. 2003, 18, 161–165. [156] Cox, M., Pichugin, A. A., El-Shafey, E. I., Appleton, Q., Hydrometallurgy 2005, 78, 137–144. [129] Philippeit, G., Angerer, J., J. Chromatogr. B 2001, 760, 237–345. [157] Gadkaree, K. P., in: Marsh, H. (Ed.), Activated Carbon Compendium, Elsevier Science Ltd., Oxford, UK 2001. [130] Koch, K. R., Coord. Chem. Rev. 2001, 216–217, 473–488. [131] Schuster, M., Schwarzer, M., Anal. Chim. Acta 1996, 328, 1–11. [132] Boch, K., Schuster, M., Risse, G., Schwarzer, M., Anal. Chim. Acta 2002, 459, 257–265. [133] Zhang, S., Pu, Q., Liu, P., Sun, Q., Su, Z., Anal. Chim. Acta 2002, 452, 223–230.  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [158] Chand, R., Watari, T., Inoue, K., Kawakita, H., Nath Luitel, H., Parajuli, D., Torikai, T., Yada, M., Miner. Eng. 2009, 22, 1277–1282. [159] Arriagada, R., Garc, R., Hydrometallurgy 1997, 46, 171– 180. [160] Syna, N., Valix, M., Miner. Eng. 2003, 16, 421–427. www.jss-journal.com 1264 E. Mladenova et al. [161] Kwak, I. S., Bae, M. A., Won, S. W., Mao, J., Sneha, K., Park, J., Sathishkumar, M., Yun, Y., Chem. Eng. J. 2010, 165, 440–446. [162] Poinern, G., Senanayake, G., Shah, N., Thi-Le, X. N., Parkinson, G. M., Fawcett, D., Miner. Eng. 2011, 24, 1694–1702. [163] Ramirez-Muniz, K., Song, S., Berber-Mendoza, S., Tong, S., J. Colloid Interface Sci. 2010, 349, 602–606. [164] Ibragimova, R. I., Vorob’ev-Desyatovskii, N. V., Tikhomolova, K. P., Ermilova, O. A., Russ. J. Appl. Chem. 2002, 75, 720–723 [165] Lagerge, S., Zajac, J., Partyka, S., Groszek, A. J., Chesneau, M., Langmuir 1997, 13, 4683–4692. J. Sep. Sci. 2012, 35, 1249–1265 [187] Bergeron, M., Beaumier, M., Hébert, A., Analyst 1991, 116, 1019–1024. [188] Godlewska-Żyłkiewicz, B., Spectrochim. Acta, Part B 2003, 58, 1531–1540. [189] De Vargas, I., Macaskie, L. E., Guibal, E., J. Chem. Technol. Biotechnol. 2004, 79, 49–56. [190] Gardea-Torresdey, J. L., Rodriquez, E., Parsons, J. G., Peralta-Videa, J. R., Meitzner, G., Cruz-Jimenez, G., Anal. Bioanal. Chem. 2005, 382, 347–352. [191] Adhikari, C. R., Parajuli, D., Kawakita, H., Inoue, K., Ohto, K., Harada, H., Environ. Sci. Technol. 2008, 42, 5486–5491. [192] Das N., Hydrometallurgy 2010, 103, 180–189. [166] Navarro, P., Vargas, C., Revista Metalurgia 2010, 46, 227–239. [193] Qing, Y., Hang, Y., Wanjaul, R., Jiang, Z., Hu, B., Anal. Sci. 2003, 19, 1417–1420. [167] Ibragimova, R. I., Mil’chenko, A. I., Vorob’evDesyatovskii, N.V., Russ. J. Appl. Chem. 2007, 80, 891– 903. [194] Moldovan, M., Gómez, M. M., Palacios, M. A., Anal. Chim. Acta 2003, 478, 209–217. [168] Leśniewska, B. A., Godlewska, I., GodlewskaŻyłkiewicz, B., Spectrochim. Acta, Part B 2005, 60, 377– 384. [169] Ruiz, M., Sastre, A. M., Guibal, E., React. Funct. Polym. 2000, 45, 155–173. [170] Chassary, P., Vincent, T., Guibal, E. React. Funct. Polym. 2004, 60, 137–149. [171] Guibal, E., Von Offenberg Sweeney, N., Vincent, T., Tobin, J. M., React. Funct. Polym. 2002, 50, 149–163. [172] Chassary, P., Vincent, T., Marcano, J. S., Macaskie, L. E., Guibal, E., Hydrometallurgy 2005, 76, 131–147. [173] Guibal, E., Ruiz, M., Vincent, T., Sastre, A., NavarroMendoza, R., Sep. Sci. Technol. 2001, 36, 1017–1040. [174] Ruiz, M., Sastre, A., Guibal, E., Sep. Sci. Technol. 2002, 37, 2143–2166. [175] Ruiz, M., Sastre, A., Guibal, E., Sep. Sci. Technol. 2002, 37, 2385–2403. [176] Oshita, K., Oshima, M., Gao, Y., Lee, K.-H., Motomizu, S., Anal. Sci. 2002, 18, 1121–1126. [177] Gao, Y., Lee, K.-H., Oshima, M., Motomizu, S., Anal. Sci. 2000, 16, 1303–1308. [178] Ramesh, A., Hasegawa, H., Sugimoto, W., Maki, T., Ueda, K., Bioresour. Technol. 2008, 99, 3801– 3809. [179] Fujiwara, K., Ramesh, A., Maki, T., Hasegawa, H., Ueda, K., J. Hazard. Mater. 2007, 146, 39–50. [180] Baba, Y., Kawano, Y., Hirakawa, H., Bull. Chem. Soc. Jpn. 1996, 69, 1255–1260. [181] Dai, X., Koeberl, C., Fröschl, H., Anal. Chim. Acta 2001, 436, 79–85. [182] Tunçeli, A., Türker, A. R., Analyst 1997, 122, 239– 242. [195] Hidalgo, M. M., Gómez, M. M., Palacios, M. A., Fresenius J. Anal. Chem. 1996, 354, 420–423. [196] Cantarero, A., Gómez, M. M., Cámara, C., Palacios, M. A., Anal. Chim. Acta 1994, 296, 205–211. [197] Brajter, K., Slonawska, K., Anal. Lett. 1988, 21, 311– 318. [198] Su, X., Wang, M., Zhang, Y., Zhang, J., Zhang, H., Jin, Q., J. Anal. At. Spectrom. 2001, 16, 1341–1343. [199] Parajuli, D., Adhikari, C. R., Kuriyama, M., Kawakita, H., Ohto, K., Inoue, K., Funaoka, M., Ind. Eng. Chem. Res. 2006, 45, 8—14. [200] Khunathai, K., Matsueda, M., Biswas, B. K., Kawakita, H., Ohto, K., Harada, H., Inoue, K., Funaoka, M., Alam, S., J. Chem. Eng. Jpn. 2011, 44, 781–787. [201] Khunathai, K., Parajuli, D., Ohto, K., Kawakita, H., Harada, H., Inoue, K., Hirota, K., Funaoka, M., Solvent Extr. Ion Exch. 2010, 28, 403–414. [202] Parajuli, D., Hirota, K., Inoue, K., Ind. Eng. Chem. Res. 2009, 48, 10163–10168. [203] Parajuli, D., Khunathai, K., Adhikari, C. R., Inoue, K., Ohto, K., Kawakita, H., Funaoka, M., Hirota, K., Miner. Eng. 2009, 22, 1173–1178. [204] Parajuli, D., Inoue, K., Kawakita, H., Ohto, K., Harada, H., Funaoka, M., Miner. Eng. 2008, 21, 61–64. [205] Rao, T. P., Kala, R., Daniel, S., Anal. Chim. Acta 2006, 578, 105–116. [206] Daniel, S., Praveen, R. S., Rao, T. P. Anal. Chim. Acta 2006, 570, 79–87. [207] Daniel, S., Gladis, J. M., Rao, T. P., Anal. Chim. Acta 2003, 488, 173–182. [208] Daniel, S., Rao, P. P., Rao, T. P., Anal. Chim. Acta 2005, 536, 197–206. [183] Tunceli, A., Turker, A. R., Anal. Sci. 2000, 16, 81–86. [209] Daniel, S., Babu, P. E. J., Rao, T. P., Talanta 2005, 65, 441–452. [184] Elçi, L., Soylak, M., Uzun, A., Büyükpatır, E., Doğan, M., Fresenius J. Anal. Chem. 2000, 368, 358–361. [210] Zheng, H., Zhang, D., Wang, W. Y., Fan, Y. Q., Li, J., Han, H. P., Microchim. Acta 2007, 157, 7–11. [185] Li, C., Chai, C., Yang, X., Hou, X., Mao, X., Talanta 1997, 44, 1313–1317. [211] Godlewska-Żyłkiewicz, B., Leśniewska, B., Wawreniuk, I., Talanta 2010, 83, 596–604. [186] Jermakowicz-Bartkowiak, D., Kolarz, B. N., Macromol. Symp. 2004, 210, 141–146. [212] Tsalev, D. L., Atomic Absorption Spectrometry in Occupational and Environmental Health Practice, Vol. II:  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com J. Sep. Sci. 2012, 35, 1249–1265 Sample Preparation 1265 Determination of Individual Elements, CRC Press, Boca Raton, Florida 1984. Emission Spectroscopy, Part II, Wiley, New York 1987. [213] Tsalev, D. L., Atomic Absorption Spectrometry in Occupational and Environmental Health Practice, Vol. III: Progress in Analytical Methodology, CRC Press, Boca Raton, Florida 1995. [216] Broekaert, J. A. C., Analytical Atomic Spectrometry with Flames and Plasmas, Wiley-VCH, Weinheim 2006. [214] Boumans, P. W. J. M., Inductively Coupled Plasma Emission Spectroscopy, Part I, Wiley, New York 1984. [215] Boumans, P. W. J. M., Inductively Coupled Plasma  C 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [217] Montaser, A., Inductively Coupled Plasma Mass Spectrometry, Wiley-VCH, New York 1998. [218] Bencs, L., Ravindra, K., Van Grieken, R., Spectrochim. Acta, Part B 2003, 58, 1723–1755. www.jss-journal.com