GAS LIQUID CHROMATOGRAPHY

Fatty acid composition of human milk (HM) is known to change considerably during lactation. However, we were unable to find data on changes of fatty acid composition of HM during the very early phase of lactation, i.e. in the first week of life. HM samples were obtained from 18 healthy lactating women every day during the first week and thereafter on the 14th and 28th days of lactation. Fatty acid composition of colostrum and mature HM samples was determined by high-resolution capillary gas-liquid chromatography. Values of the n-6 essential fatty acid, linoleic acid, in HM did not change significantly during the first month of lactation, whereas values of the n-3 essential fatty acid, alpha-linolenic acid, showed significant increases during the first 2 weeks of lactation (1st day: 0.49 [0.12], % weight/weight, median [ranges from the 1st to the 3rd quartile], 14th day: 0.69 [0.31], p < 0.05). In contrast, values of the n-6 long-chain metabolites, eicosadienoic-, dihomo-gamma-linolenic- and arachidonic acid, as well as the values of the n-3 long-chain metabolites, eicosatrienoic-, and eicosapentaenoic acid exhibited significant decreases during the entire period investigated. The principal n-3 long-chain metabolite, docosahexaenoic acid, showed a significant increase between the 3rd and 14th days, but a significant decrease between the 14th and 28th days (3rd day: 0.15 [0.13], 14th day: 0.28 [0.11], p < 0.05, 28th day: 0.19 [0.12], p < 0.01). There were statistically significant positive correlations between arachidonic and docosahexaenoic acid values on the 1st (r = 0.67, p < 0.01), 5th (r = 0.56, p < 0.05) and the 6th (r = 0.53, p < 0.05) days of lactation. Fatty acid composition of HM changes significantly even during the first week of lactation. The lack of positive correlation between essential fatty acids and their long-chain metabolites suggests that it is not only the availability of essential fatty acids that influences the fatty acid composition of human colostrum.

Densities, viscosities and refractive indices have been determined for mixtures of acetophenone with N,N-dimethylethanolamine or with N,N-diethylethanolamine over the entire composition range at temperatures of (303.15, 313.15 and 323.15) K. The viscosity values were fitted to the Krishnan-Laddha and McAllister models. The thermophysical properties under study were also fitted to the Jouyban-Acree model. The excess values were correlated using the Redlich-Kister polynomial equation. It was found that, in all cases, the obtained data were correlated very well by the corresponding models. The molecular interactions existing between the components are also discussed.

Biodiesel, as an alternative fuel, is gradually receiving more popularity for use in internal combustion engines. However questions continue to arise with regard to its compatibility with elastomeric materials. The present work aims to investigate the comparative degradation of physical properties for different elastomers [e.g. ethylene propylene diene monomer (EPDM), silicone rubber (SR), polychloroprene (CR), polytetrafluroethylene (PTFE) and nitrile rubber (NBR)] upon exposure to diesel and palm biodiesel. Static immersion tests in B0(diesel), B10 (10% biodiesel in diesel), B20, B50 and B100(biodiesel) were carried out at room temperature (25 °C) for 1000 h. Different physical properties like, changes in weight and volume, hardness and tensile strength were measured at every 250 h of immersion time. Compositional changes in biodiesel due to exposure of different elastomers were investigated by Gas chromatography mass spectroscopy (GCMS). The overall sequence of compatible elastomers in palm biodiesel is found to be PTFE > SR > NBR > EPDM > CR.

http://www.sciencedirect.com/science/article/pii/S0360544210007139

Our objective is to demonstrate the analytical capabilities of Advanced Surface Logging or Advanced Mud Logging (AML), the results borne from an extensive use of wellsite techniques and their use in time-critical situations. The work revolves around ascertaining and characterizing from the surface the nature of fluids found downhole using a number of integrated analytical techniques on oil samples and rock cuttings. We aim to evaluate the reservoir fluid properties flowing from the fractures and fluids which are suspected to be present within the pores of the reservoir matrix via cross-referencing multiple sample mediums.
The work studies data collected from a well in the Middle East; “Well-A”, which was drilled as a producer from the Upper-Middle Jurassic (UMJ) Formations and an appraisal from the porous interval of the Lower Jurassic formation (LJ). The primary target of the operating company was to determine the in-situ fluid characteristics of the UMJ Formations. The communication between these two intervals as well as the contact depth is unknown and crucial at the current stage of the field development.
Reservoir and hydrocarbon fluid characterization was investigated using cuttings samples taken from Well-A. All samples were analyzed in-lab, post-drilling using Advanced Mudlogging (AML) techniques such as Thermal Extraction Gas Chromatography (TEGC), Chemical Elemental Analysis and Mineralogical analysis (the latter two performed using X-Ray based techniques). Additional Mudlogging datasets gathered in real-time during drilling were integrated within the interpretation including Advanced Mud Gas (Methane to Toluene), together with the Computer Processed Image Logs and PVT test data provided by the operator. Finally, three dead oil samples from the tested intervals were analyzed in-lab with TEGC.
The chromatographic analysis of the commercially produced oil from the UJ showed a bimodal distribution which was interpreted as a mix of two different maturity fluids. We were able to trace the individual levels from which these two fluids were most probable to originate, by comparing the chromatographic characteristics of these oils across the TEGC results from the cuttings analysis. Furthermore, the in-lab geochemical analysis supported the understanding of the fluid mechanism within this reservoir interval. This interpretation resulted in potentially identifying a sub interval which could yield a higher gravity oil than initially tested and potentially transform this, now unproductive interval, into a prospect.
The innovative workflow, integrating all formation evaluation data collected from rock cuttings and mud gas data was applied for the first time at this level of complexity. Although prior studies investigated thepotential of integrating multiple datasets to determine reservoir fluid characteristics, never before, was such an integrated approach utilized based specifically on surface logging solutions. The case study demonstrated the value of supporting interpreters to bolster their interpretations thanks to data coming from separate independent sources.

"La chromatographie en phase gazeuse (CPG) est toujours un outil très utilisé dans le domaine de la chimie analytique et du contrôle, en particulier en chimie environnementale où les besoins deviennent de plus en plus nombreux et variés. Sa popularité s’étend même au grand public par l’intermédiaire des médias, où il n’est pas exceptionnel de voir des appareils de chromatographie en phase gazeuse dans des reportages télévisés sur des thèmes les plus divers (cosmétologie, dopage, archéologie, pétrochimie…).
Cet article fait suite à celui paru en 1998 (1) et il nous a paru intéressant de réactualiser les caractéristiques des appareils de CPG commercialisés en ce début de siècle et de millénaire. Si aucune grande nouveauté technologique n’est apparue dans ce domaine, la grande évolution sur les appareils disponibles se situe surtout au niveau du choix des injecteurs-vaporisateurs proposés par les fabricants. Dans le précédent article, nous avions décrit en détail le fonctionnement des différents détecteurs ; c’est pourquoi, nous allons décrire ici, celui des injecteurs-vaporisateurs classiques. Puis, des tableaux synoptiques des principaux appareils rencontrés sur le marché français seront donnés, en nous basant sur les informations fournies par les constructeurs.
Mots clés : chromatographie en phase gazeuse, appareillage, aspects techniques, injecteur."

A  simple,  robust,  precise  HPLC  method  was  developed  and  the
method  has  been  validated  for  the  estimation  of  valsartan  and
nebivolol  simultaneously  in  its  combined  dosage  forms  as  well  as
individual formulations. Both the compounds are well resolved in a
isocratic  method  by  using  the  mobile  phase  composition  of
acetonitrile: methanol: pH4.0 0.02M Potassium hydrogen phosphate
buffer in the ratio of 50:20:30 v/v at a flow rate of 1.0mL/min using a
C-18 column. The detection was carried out at 210nm.. The retention
time  of  Nebivolol  and  Valsartan  were  2.5  min  and  4.3  min
respectively.  The  developed  method  was  validated  for  specificity,
linearity,  precision,  accuracy,  limit  of  detection  (LOD),  limit  of
quantification (LOQ) and robustness as per ICH guidelines. Linearity
for Nebivolol and Valsartan were found in the range of 48-112 µg/ml
and  3.0-7.0  µg/ml,  respectively.  The  percentage  recoveries  for
Nebivolol  and  Valsartan  ranged  from  98.9-100.8  %  and  98.9-101.1
%,  respectively.  The  proposed  method  could  be  used  for  routine
analysis of Nebivolol and Valsartan in their combined dosage forms

A new rapid, precise and sensitive reverse phase high performance
liquid chromatographic (RP-HPLC) method has been developed and
validated  for  the  estimation  of  Perindopril  and  Amlodipine
simultaneously  in  combined  dosage  form.  The  two  components
Perindopril  and  Amlodipine  were  well  resolved  on  an  isocratic
method,  C18  column,  utilizing  a  mobile  phase  composition  of
acetonitrile:  methanol:  a  mixed  buffer  of  0.02M  Potassium
dihydrogen  phosphate  buffer  and  0.02M  Sodium  dihydrogen
Phosphate buffer with 1mL Tri ethyl amine (40:20:40), v/v, pH 5.0)
at  a  flow  rate  of  1.0  mL/min  with  UV  detection  at  226  nm.  The
retention time of Perindopril and Amlodipine were 2.9 min and 4.9
min  respectively.  The  developed  method  was  validated  for
specificity,  linearity,  precision,  accuracy,  limit  of  detection  (LOD),
limit of quantification (LOQ) and robustness as per ICH guidelines.
Linearity for Perindopril and Amlodipine were found in the range of
48-112 µg/ml and 60.0-140.0 µg/ml, respectively. The percentage
recoveries for Perindopril and Amlodipine ranged from 98.9-100.4 %
and 98.9-100.7 %, respectively. The proposed method could be used
for routine analysis of Perindopril and Amlodipine in their combined
dosage forms.

Metabolite profiling has been used to assess the potential for unintended composition changes in potato (Solanum tuberosum L. cv. Desirée) tubers, which have been genetically modified (GM) to reduce glycoalkaloid content, via the independent down-regulation of three genes SGT1, SGT2 and SGT3 known to be involved in glycoalkaloid biosynthesis. Differences between the three groups of antisense lines and control lines were assessed using liquid chromatography-mass spectrometry (LC-MS) and gas chromatography (GC)-MS, and data analysed using principal component analysis and analysis of variance. Compared with the wild-type (WT) control, LC-MS revealed not only the expected changes in specific glycoalkaloid levels in the GM lines, but also significant changes in several other metabolites, some of which were explicable in terms of known pathways. Analysis of polar and non-polar metabolites by GC-MS revealed other significant (unintended) differences between SGT lines and the WT, but also between the WT control and other control lines used.

Detection of foreign fat in milk fat can be performed by analyzing triacylglycerols (TAGs) by gas-liquid chromatography (GLC) using the standardized methodology. The standard methodology recommends the use of a packed column, which allows the separation of milk TAGs according to their chain length (total carbon number). This procedure is not widely applied because these columns are not commercially available. This study describes a fast methodology by using a short apolar open-tubular capillary column. The developed experimental conditions can be used to obtain the chromatographic resolution required in the standardized procedure, and the separation of milk fat TAGs (C24 to C54) is achieved in less than 4 min. As indicated by the standardized method, the quantification was performed by calibration using the certified reference material CRM-519 butterfat as standard substance. The methodology was fully validated and relative repeatability values were compared with the values provided...

Residues of ethion were estimated in cucumber by gas liquid chromatography following three applications of the insecticide at 375 and 750 g a.i ha−1. The average initial deposits of ethion on cucumber fruits were found to be 2.40 and 4.97 mg kg−1 at single and double dosages, respectively. Residues of ethion dissipated below the maximum residue limit (MRL) of 0.5 mg kg−1 in 7 days. Half-life (T1/2) for degradation of ethion on cucumber was observed to be 2.92 days at recommended dosage. A waiting period of 7 days is suggested for safe consumption of cucumber.

In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO2/Al2O3 membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70°C employing 157.04g catalyst per unit volume of the reactor and 0.21cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor. © 2010 Elsevier Ltd.

http://ac.els-cdn.com/S0960852410014574/1-s2.0-S0960852410014574-main.pdf?_tid=74bcbdf2-025e-11e4-8ea3-00000aab0f27&acdnat=1404356723_f959262287254ffe4bce3abeee7084d9 
http://www.sciencedirect.com/science/article/pii/S0960852410014574