No.

SSI-GCMS-1402

Gas Chromatograph Mass Spectrometer

Analysis of Pesticides in Baby Foods Using

No. GCMS-1402 a GCMS-TQ8030 GC/MS/MS, Part II

■ Introduction
Contamination of food products with pesticides is a Triple quadrupole GC/MS/MS has emerged as an
growing concern because of recognized adverse health important technique for analysis of trace-level
effects, increasing world-wide usage of pesticides, and contaminants in complex matrices. Operation of the
increasing imports of raw foodstuffs from foreign triple quadrupole GC/MS/MS in the Multiple Reaction
sources. The concern is particularly acute for baby Monitoring (MRM) mode provides unmatched
foods because of the high vulnerability of babies to sensitivity and selectivity for detection and quantitation
health effects from synthetic chemicals such as of target pesticides at low concentrations in the
pesticides. presence of background interferences. Most
co-extracted matrix interferences are minimized or
Gas chromatography mass spectrometry (GCMS) has completely eliminated using the MRM mode.
been used extensively to identify and quantify
trace-level pesticides in food matrices; the most This application note presents instrument
significant challenges have been matrix interference configuration, operating parameters, and analytical
and achievement of meaningful health-based results for analysis of 36 pesticides from various
detection limits for the compounds of interest. The chemical classes in a QuEChERS extract of baby food
QuEChERS (Quick Easy Cheap Effective Rugged and using the Shimadzu GCMS-TQ8030 triple quadrupole
Safe) sample preparation method1 has helped to GC/MS/MS (Figure 1). Results were evaluated for
overcome some of the problems of matrix interference, calibration linearity, analytical precision, and accuracy
and commercialization of QuEChERS kits has in a baby food matrix. Selectivity as a function of
promoted widespread screening of foodstuffs for trace variable mass spectral resolution settings on the two
pesticides. But matrix interferences still present a sets of quadrupoles, Q1 and Q3, is also discussed.
significant challenge for analysis of trace-level
pesticides in foods, even after QuEChERS extraction
and cleanup.

Figure 1: Shimadzu GCMS-TQ8030 Triple Quadrupole GC/MS/MS

 No. SSI-GCMS-1402

■ Experimental
The analyses were conducted using a Shimadzu GCMS-TQ8030 allows optimization of the collision
GCMS-TQ8030 triple quadrupole GC/MS/MS. The energy for each MRM transition, providing ultimate
GCMS-TQ8030 was operated in the multiple reaction sensitivity. The instrument configuration and operating
monitoring (MRM) mode, using the optimized MRM conditions, including MRM transitions and optimized
transitions and collision energies detailed in the collision energies are shown in Tables 1 and 2, below.
Shimadzu GC/MS/MS Pesticide Database.2 The

Table 1: Instrument Configuration and Operating Conditions for Analysis of Pesticides

Instrument GCMS-TQ8030

250 °C
Inlet Single taper gooseneck splitless liner with glass wool (Restek 23322.5)
Splitless injection, sampling time 1 minute
RXI-5Sil MS, 30 m x 0.25 mm x 0.25 µm (Restek 13623)
Column Helium carrier gas
Constant linear velocity 47 cm/second
95 °C, hold 1.5 minute
20 °C/minute to 300 °C, hold 5.25 minutes
Oven Program
MS interface 250 °C
Analysis time 18 minutes
200 °C
Ion Source
Electron ionization (EI), 70 eV
Multiple Reaction Monitoring (MRM)
Operation Mode Argon gas, 200 kPa
Unit Resolution (0.8 u on Q1 and Q3, FWHM definition)
Table 2: GCMS-TQ8030 MRM Transitions and Collision Energies (CE)

Compound Tx #1 CE Tx #2 CE Tx #3 CE Compound Class

Methamidophos 141.0>95.0 8 141.0>126.0 4 141.0>79.0 22 OP insecticide

Dichlorvos 185.0>93.0 14 185.0>109.0 14 185.0>63.0 22 OP insecticide

Mevinphos 192.0>164.0 4 192.0>127.0 12 192.0>109.0 24 OP insecticide

Acephate 136.0>94.0 14 136.0>119.0 8 136.0>64.0 22 OP insecticide

2-Phenylphenol 170.1>141.1 24 170.1>115.1 28 170.1>155.1 14 Phenolic fungicide

Omethoate 156.0>110.0 8 156.0>141.0 4 156.0>79.0 22 OP insecticide

Dimethoate 125.0>79.0 8 125.0>47.0 14 125.0>62.0 10 OP insecticide

gamma-BHC (Lindane) 218.9>182.9 8 218.9>144.9 20 218.9>109.0 28 OCl insecticide

Diazinon 304.1>179.1 10 304.1>162.1 8 304.1>137.1 26 OP insecticide

Vinclozolin 285.0>212.0 12 285.0>178.0 14 285.0>241.0 4 Fungicide

Carbaryl 144.10>116.1 12 144.10>89.0 38 144.10>65.0 28 Carbamate

Metalaxyl 249.2>190.1 8 249.2>146.1 22 249.2>217.1 6 Fungicide

Methiocarb 168.1>153.0 8 168.1>109.0 14 168.1>45.0 22 Carbamate

Pirimiphos-methyl 305.1>180.1 8 305.1>290.1 12 305.1>125.0 28 Phosphorothioate

Malathion 173.1>99.0 14 173.1>127.0 6 173.1>145.0 6 OP insecticide

Fenthion 278.0>109.0 20 278.0>125.0 20 278.0>169.0 14 Organothiophosphate

 No. SSI-GCMS-1402

Chlorpyrifos 313.9>257.9 14 313.9>285.9 8 313.9>193.9 28 OP insecticide

Dicofol deg. (DCBP) 250.0>139.0 14 250.0>215.0 8 250.0>111.0 28 OCl insecticide

Triphenylmethane (IS) 244.1>167.1 10 244.1>243.1 10 Internal Standard

Cyprodinil 224.1>208.1 16 224.1>197.1 22 224.1>131.1 14 Fungicide

Thiabendazole 201.1>174.1 16 201.1>130.1 26 201.1>92.0 28 Fungicide

Imazalil 215.0>173.0 6 215.0>159.0 6 215.0>145.0 26 Fungicide

Myclobutanil 179.1>125.0 14 179.1>152.0 8 179.1>90.0 26 Fungicide

Endrin 262.9>191.0 30 262.9>193.0 28 262.9>228.0 22 OCl insecticide

Phenhexamid 177.0>113.0 15 177.0>78.0 20 Fungicide

Endosulfan sulfate 386.8>288.0 10 386.8>252.9 16 386.8>240.9 22 OCl insecticide

p,p’-DDT 235.0>165.0 24 235.0>199.0 16 235.0>149.0 40 OCl insecticide

Triphenyl phosphate (SS) 326.1>170.1 15 326.1>215.1 20 Surrogate Standard

Propargite 135.1>107.1 16 135.1>77.0 24 135.1>95.0 14 Organosulfite

Iprodione 314.0>245.0 12 314.0>56.0 22 314.0>271.0 8 Fungicide

Bifenthrin 181.1>166.1 12 181.1>153.1 8 181.1>179.1 12 Pyrethroid

Fenpropathrin 265.1>210.10 12 265.1>172.1 14 265.1>89.0 28 Pyrethroid

Phosalone 182.0>111.0 14 182.0>138.0 8 182.0>102.0 14 OP insecticide

Azinphos-methyl 160.1>132.1 6 160.1>77.0 20 160.1>51.0 28 OP insecticide

Permethrin-1 183.1>168.1 14 183.1>165.1 14 183.1>153.1 14 Pyrethroid

Coumaphos 362.1>109.0 20 362.1>226.1 15 362.1>134.0 5 Phosphorothioate

Permethrin-2 183.1>168.1 14 183.1>165.1 14 183.1>153.1 14 Pyrethroid

Deltamethrin 252.9>93.0 20 252.9>171.9 8 252.9>77.0 26 Pyrethroid

A sample of blended pears was used as the test sample procedure. The sample preparation did not involve
matrix; an organic variety was selected so it would be concentrating or diluting the sample, so
free from background pesticide contamination. The concentrations expressed in ng/mL (parts-per-billion,
sample matrix was extracted and subjected to cleanup ppb) in the calibration standards and extracts are
using the QuEChERS procedure. Calibration was equivalent to ng/g (parts-per-billion, ppb) in the
conducted using the matrix-matched internal standard original sample.

■ Results and Discussion

Chromatography
The total ion chromatogram (TIC) acquired in the MRM than a typical TIC acquired in the full-scan mode. The
mode for the pesticide standard is shown in Figure 2, effect of initial column temperature on
and illustrates the chromatographic separation of the chromatographic performance is important when the
target pesticides in this study. In the MRM mode, the QuEChERS procedure is used; the injection solvent,
TIC for each analyte is the sum of the signal for each acetonitrile, produces some unusual chromatographic
MRM transition for that particular compound, so the effects at temperatures below 90 °C.3
appearance of the chromatogram is slightly different
 No. SSI-GCMS-1402

Figure 2: Total Ion Chromatogram (TIC) of Matrix-Matched Pesticide Standard Run in the MRM Mode

Matrix-Matched Calibration Precision and Accuracy

Using the matrix-matched calibration approach, five Eight replicate injections of the 1.0 and 5.0 ng/mL
calibration standards were prepared in a blended pears matrix-matched standards were analyzed to assess the
extract over the range of 1-200 ng/mL (ppb). precision and accuracy of the method near the low end
Triphenylmethane was used as the internal standard of the calibration range. The mean concentration
(IS) and was held constant at 10 ng/mL; triphenyl and %RSD for the replicate analyses are presented in
phosphate was used as a surrogate standard (SS) at 20 Table 3.
ng/mL in all standards. The calibration standards were
analyzed using the instrument conditions outlined In conjunction with the precision and accuracy study, a
above. The detector voltage (electron multiplier) was matrix blank (unspiked sample matrix) was analyzed to
adjusted to give acceptable response at the lowest check for background levels of the target compounds.
calibration level and avoid saturation at the highest Discrete chromatographic peaks for approximately
calibration level. one-third of the target compounds were observed in
the matrix blank, indicating that these pesticides were
Response factors were calculated and percent relative present in the native baby food matrix. Concentrations
standard deviation (%RSD) determined using of the native pesticides in the matrix were all below 1.0
GCMSsolution software. The precision of the ng/mL, and account for recovery anomalies at the
calibration was evaluated using the correlation lowest spike levels (1.0 ng/mL). The effect of native
coefficient (r) and %RSD of the response factors for pesticides in the calibration standards can be avoided
each analyte, as tabulated in Table 3. Linearity, as by preparing standards in solvent instead of matrix.
evaluated by the correlation coefficient, was 0.999 or
better for all 36 compounds. In many cases where the
RSD for the response factors was greater than 20%
(e.g. thiabendazole and imazalil), the presence of
native pesticides in the matrix contributed to the signal
for the lowest concentration standards and accounts
for the high %RSD. When the low-level calibration
standard is not included in the calculation, RSD is less
than 20% overall.
 No. SSI-GCMS-1402

Table 3: Matrix Matched Calibration, Precision, and Accuracy Results for Pesticides Analysis

Calibration Results Precision and Accuracy

Matrix
Blank
Compound 1.0 ppb 5.0 ppb
Mean Mean
Mean RF RF %RSD r ppb %RSD %RSD
(ppb) (ppb)
Methamidophos 0.91 14 >0.999 0.29 0.93 10 3.93 6

Dichlorvos 0.38 6 >0.999 ND 0.84 17 5.46 6

Mevinphos 0.71 16 >0.999 ND 0.82 6 3.71 7

Acephate 0.53 17 >0.999 ND 0.65 13 2.85 13

2-Phenylphenol 0.90 18 0.999 0.60 1.05 8 3.14 5

Omethoate 1.34 9 0.999 ND 0.92 9 3.91 5

Dimethoate 0.33 20 >0.999 0.44 0.91 17 2.92 8

gamma-BHC (Lindane) 0.44 4 >0.999 ND 0.88 12 5.50 4

Diazinon 0.56 14 >0.999 0.02 0.92 14 5.26 6

Vinclozolin 0.23 15 >0.999 ND 0.75 41 6.05 9

Carbaryl 1.60 10 >0.999 ND 0.69 7 3.91 6

Metalaxyl 0.37 25 >0.999 ND 0.86 19 5.57 6

Methiocarb 1.92 21 >0.999 0.27 0.65 28 3.48 7

Pirimiphos-methyl 0.40 21 >0.999 ND 0.88 15 5.26 9

Malathion 1.14 8 >0.999 0.13 1.01 11 5.21 6

Fenthion 1.12 7 0.999 0.03 1.04 12 5.42 7

Chlorpyrifos 0.58 19 >0.999 0.06 0.84 17 5.29 5

Dicofol deg. (DCBP) 0.53 15 >0.999 ND 0.87 18 5.31 6

Triphenylmethane (IS) N/A N/A N/A NA NA 5 NA 7

Cyprodinil 0.91 8 0.999 0.30 1.05 13 4.63 6

Thiabendazole 2.93 34 >0.999 0.89 0.86 5 1.81 6

Imazalil 0.83 27 >0.999 0.78 0.87 7 2.52 6

Myclobutanil 1.38 3 >0.999 0.19 1.01 4 4.71 7

Endrin 0.07 5 >0.999 ND 1.04 15 4.60 13

Phenhexamid 0.41 6 >0.999 0.23 0.82 20 4.31 12

Endosulfan sulfate* 0.05 34 >0.999 ND ND ND 3.60 26

p,p’-DDT 1.85 7 >0.999 ND 0.98 11 4.95 5

Triphenyl phosphate (SS) N/A N/A N/A 19.80 19.71 4 19.24 7

Propargite* 1.24 12 >0.999 ND 0.83 32 2.27 15

 No. SSI-GCMS-1402

Iprodione* 0.05 20 >0.999 ND ND ND 1.68 49

Bifenthrin 4.72 9 0.999 ND 0.96 8 4.01 3

Fenpropathrin 0.34 8 >0.999 ND 0.65 35 4.31 12

Phosalone 1.26 2 >0.999 0.08 0.96 10 4.43 6

Azinphos-methyl 1.64 9 >0.999 ND 1.01 12 4.01 7

Permethrin-1 0.76 15 >0.999 ND 0.91 12 5.64 17

Coumaphos 0.41 16 >0.999 0.05 0.80 17 4.47 5

Permethrin-2 0.52 2 >0.999 ND 0.50 14 2.79 8

Deltamethrin 0.16 16 0.999 ND 0.75 13 4.41 7

Note: for most compounds the low-level calibration standard was 1.0 ng/mL. For compounds indicated with an *, the low-level
calibration standard was 5.0 ng/mL.

Selectivity as a Function of Mass Spectral Resolution

Resolution settings on the GCMS-TQ8030 are ions strike the detector, but they also increase the
expressed using the FWHM (Full Width at Half corresponding noise levels, so the resulting
Maximum) definition. Three resolution settings are signal-to-noise ratios (SNR) are actually reduced, and
available for each set of quadrupoles when operating analyte detection limits go up. Unit (0.8 u) or High (0.6
in the MRM mode (Table 4), and the resolution can be u) resolution settings reduce overall signal intensity
defined independently for Q1 and Q3, using any (fewer ions to the detector), but noise levels are also
combination of the three settings. In most cases, Unit significantly reduced so SNR and analyte detection
resolution (0.8 u) for both Q1 and Q3 provides the best limits can be greatly improved. This principle is
combination of sensitivity and selectivity, however Q1 illustrated using 10 replicate injections of an
and Q3 mass spectral resolution settings can be octafluoronaphthalene (OFN) standard, as shown in
adjusted individually for each analyte to provide a Table 5. Even though signal intensity using the
customized method when needed. Q1=Low and Q3=Low (Low/Low) resolution setting is
approximately 4 times higher than when using the
The resolution settings that are chosen can have an Unit/Unit setting, the corresponding noise levels are so
enormous impact on signal intensity, noise levels, high with Low/Low resolution that SNR is dramatically
compound detection limits, and selectivity against and negatively impacted. In general, the Unit/Unit
background interferences. Low resolution settings (e.g. setting provides the best overall balance of high signal
3.0 u) increase analyte signal intensity because more intensity and low noise.

Table 4: Resolution Settings for Q1 and Q3 on the GCMS-TQ8030

Resolution FWHM
High 0.6 u
Unit 0.8 u
Low 3.0 u
 No. SSI-GCMS-1402

Table 5: Effect of Resolution Settings on Signal Intensity and SNR (10 replicate injections of OFN)

Q1 = Low, Q3 = Low Q1 = Unit, Q3 = Unit

Run # Peak Area SNR Run # Peak Area SNR
1 172,178 67 1 46,829 32,867
2 191,542 83 2 45,518 49,634
3 183,778 76 3 41,580 39,014
4 169,255 69 4 39,213 46,252
5 168,489 73 5 41,723 36,260
6 179,107 65 6 43,647 33,482
7 200,396 86 7 40,716 26,709
8 176,782 69 8 37,946 34,634
9 169,624 72 9 44,807 52,017
10 169,073 72 10 40,602 40,126
Average 178,022 73 Average 42,658 41,100
%RSD 6.1 %RSD 6.8

Perhaps even more important than signal and noise This principle is illustrated in Figure 3. When using
considerations, is the impact mass spectral resolution Low/Low resolution settings (black trace), the m/z 158
can have on analyte selectivity against co-eluting → 130 transition for glutaric acid-2TMS in this urine
matrix interferences. When a low resolution setting is sample was subject to interference from close-eluting
used (e.g. 3.0 u), the m/z range of ion fragments that contaminants with similar precursor-product ion pairs.
are allowed to strike the detector is broad, and allows As the resolution was increased, the m/z range of
non-specific fragments from compounds other than fragments allowed to strike the detector was narrowed
the target analyte (i.e. matrix interferences) to be from 3.0 u to 0.8 u, and the interference was
included in the measurement. Narrowing the m/z eliminated. The signal intensity is reduced with
range to Unit (0.8 u) or High (0.6 u) resolution Unit/Unit resolution, but this is due primarily to
minimizes the potential of there being close-eluting eliminating the fragments from sources other than the
contaminants with similar m/z fragments. Compound target compound, and makes the resulting
specificity is achieved by using unique MRM transitions quantitation of the target more accurate.
with customized resolution settings for each
compound, and provides clean MRM chromatograms
even in the presence of matrix interferences with
common precursor or product ions.

Black: Q1 Low, Q3 Low

Pink: Q1 Unit, Q3 Low
Blue: Q1 Unit, Q3 Unit

Figure 3: One MRM Transition, 158 → 130, for Glutaric Acid-2TMS in Urine Analyzed Using Three Different Resolution Settings for Q1
and Q3: Low/Low (Black), Unit/Low (Pink), and Unit/Unit (Blue)
 No. SSI-GCMS-1402

The effect of resolution settings on compound prevent proper integration and confirmation of
selectivity can also be seen in the matrix-matched compound identity using peak ratios. The Unit/Unit
pesticide standards used for the baby food project. resolution setting narrowed the m/z range on both Q1
Figure 4 shows the overlaid MRM chromatograms for and Q3 to eliminate the fragments from close-eluting
mycyclobutanil (1.0 ng/mL) at three different resolution matrix interference, and prevent them from
settings for Q1 and Q3: Low/Low, Unit/Low, and contributing to the signal. The peak was easily and
Unit/Unit. When using the Low/Low resolution setting, accurately integrated, and peak area ratios for the
background interference from the baby food matrix is three individual transitions can be used for
clearly evident, and produces interferences which confirmation of compound identity.

MS Resolution: Q1 Unit, Q3 Unit

MS Resolution: Q1 Unit, Q3 Low

MS Resolution: Q1 Low, Q3 Low

Figure 4: MRM Chromatograms for Mycyclobutanil at Three Settings of MS Resolution

For most analyses, the Unit/Unit resolution settings for Mass spectral resolution for Q1 and Q3 on the
Q1 and Q3 provide the best combination of sensitivity GCMS-TQ8030 can be adjusted individually for each
and selectivity. Lower resolution settings (Unit/Low or “event”, or set of MRM transitions for a specific
Low/Low) allow matrix contaminants to interfere with analyte. With this feature, mass spectral resolution in
quantitation, and are not recommended. Higher an analytical method can easily be customized to
resolution settings (e.g. High/Unit or High/High) which optimize response and chromatographic selectivity for
narrow the m/z range to 0.6 u on one or both sets of each analyte. An example method illustrating this
quadrupoles can also be used when matrix customization is shown in Figure 5 below.
interference is severe. In this case, signal intensity will
be reduced, but interference will be eliminated, and
quantitation accuracy will be improved.
 No. SSI-GCMS-1402

Figure 5: Example of an MRM Method with Q1 and Q3 Resolution Settings

■ Conclusion
Detection of pesticides was demonstrated at quantitation, and are not recommended. Higher
single-digit ng/mL (ppb) levels in a complex sample resolution settings (e.g. High/Unit or High/High) which
matrix, and linear calibration was confirmed from narrow the m/z range to 0.6 u on one or both sets of
1-200 ng/mL in matrix-matched standards. Precision quadrupoles can also be used when matrix
and accuracy were established by replicate analyses of interference is severe. In this case, signal intensity will
matrix spiked aliquots at 1.0 and 5.0 ng/mL, and found be reduced, but interference will be minimized or
to have single-digit %RSD for those pesticides that did eliminated, and quantitation accuracy will be improved.
not appear in the sample matrix. Approximately A powerful feature of the Shimadzu GCMS-TQ8030 is
one-third of the pesticides in this study were also the ability to adjust the Q1 and Q3 resolution settings
detected in the un-spiked baby food extract at individually to customize the method.
concentration below 1.0 ng/mL. The concentration
range used in this study covers the Maximum Residue A Shimadzu GCMS-TQ8030 system operated in the
Levels (MRL) for many pesticides, and validates the MRM mode was shown to be a rapid, sensitive, and
utility of the MRM mode for analysis of pesticides in selective technique for analysis of various classes of
complex food matrices. pesticides in baby foods in the range required for many
regulatory MRLs. Reliable, precise measurements were
For most analyses, the Unit/Unit resolution settings for obtained for 36 pesticides. The Shimadzu GC/MS/MS
Q1 and Q3 provide the best combination of sensitivity Pesticide Database simplified development of the MRM
and selectivity. Lower resolution settings (Unit/Low or method.
Low/Low) allow matrix contaminants to interfere with

■ References
1. AOAC Official Method 2007.01, Pesticide Residues in Foods by Acetonitrile Extraction and Partitioning with
Magnesium Sulfate (2007).
2. Shimadzu GC/MS/MS Pesticide Database (October, 2012).
3. Analysis of Organophosphorus Pesticides in Baby Foods Using a Triple-Quadrupole GC/MS/MS System
Shimadzu Application News No. GCMS-1304 (February, 2013).

■ Acknowledgements
The authors wish to acknowledge Restek Corporation, Bellefonte, PA for useful discussions and advice regarding
chromatographic conditions and column selection. Restek also provided the GC columns, standards, and the
QuEChERS sample extracts used in this study.

First Edition: January 2014

For Research Use Only. Not for use in diagnostic procedures.

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