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Screening for 34 Pesticides in Hops Using GC-MS/MSRobert H. Clifford, Nicole Lock, Laura Chambers, William Lipps, Zhuangzhi Max Wang, Shimadzu Scientific Instruments, Columbia, MD, USA
Introduction
From a consumer safety point-of-view, quantitation of pesticide residues in hops has begun to attract wide interest. There are several problems associated with analysis of pesticide residues in hops. First and foremost, there are very few regulatory guidelines established to define which pesticides to include or what the detection limits should be. In fact the US governments 40 CFR Part 180 states individual tolerances must be established for miscellaneous commodities intentionally not included in any group including hops. Secondly the matrix is very complex with significant interferences. Finally, sample load is growing exponentially, so the chosen method must be quick and easy to perform.
Introduction
Trace-level pesticide analysis in complex food matrices has been done for many years with similar challenges, thus many of the analytical protocols emerging for the hops matrix are based on these well-established techniques. Triple-quadrupole GC-MS/MS operated in MRM mode provides significant sensitivity and selectivity, but method development can be expensive and time consuming.
This poster describes a streamlined method development process for analysis of 34 pesticide residues in hops using a QuEChERS sample preparation method, followed by GC-MS/MS detection and quantitation. The pesticides are from 5 classes of compounds including organonitrogen, organophosphorus, organochlorines, carbamates, and synthetic pyrethroids.
Experimental
Compound ListFor this study 34 pesticides were selected for analysis based on the types of pesticides that are commonly used in hop production. The list includes several different compound classes (Table 1).
Organonitrogen Compounds
Synthetic Pyrethroid Compounds
Organophosphorus Compounds
Bupirimate Bifenthrin ChlorpyrifosEtofenprox Permethrin DiazinonEtridiazole (Terrazole) Cyfluthrin MalathionFenarimol Deltamethrin Mevinphos (Phosdrin)Flutriafol Flucythrinate PhosaloneMGK-264 Lambda-cyhalothrin Pirimiphos methylMyclobutanil Tefluthrin Carbamates and othersPaclobutrazol Transfluthrin MetalaxylPenconazole Organochlorines compounds 2-PhenylphenolTebuconazole (Folicur) Dichlorvos (DDVP) VinclozolinTerbuthylazine Endosulfan sulfateTriadimefon gamma-BHC (Lindane)Triadimenol (Baytan) p,p'-DDT
Table 1: Selected Pesticide Compound Classes Included Organonitrogens, Synthetic Pyrethroids, Organochlorines, Organophosphates, and Carbamates
ExperimentalMethod DevelopmentThe most difficult part of any triple quadrupole method development process is determination and optimization of the Multiple Reaction Monitoring (MRM) transitions and collision energies (CE). For this study, the Shimadzu Smart Pesticide Database was used as the foundation for creating the MRM analysis method. The Smart Pesticide Database includes up to six fully optimized MRM transitions and CEs for 479 pesticides and Retention Indices (RI) for accurately predicting compound retention times. The transitions and CEs in the database were optimized using the Shimadzu GCMS-TQ8040 triple quadrupole GC-MS/MS. Figure 1 shows a portion of the Smart Pesticide Database and the method, compound, and transition information.
Figure 1: Example of Information Found in the Smart Pesticide Database Used to Create an MRM Analysis Method
Compound Information Transition InformationMethod Information
Experimental
A few of the target pesticides were not included in the Smart Pesticide Database. For these compounds, the MRM Optimization Tool was used to automatically determine the optimized MRM transitions and collision energies (CE). Once determined, the new transitions are added to the Smart Pesticide Database. Figure 2 shows the graphic results from the MRM Optimization Tool, with six transitions for two of the pesticides.
Product m/z 123.05>95.10 219.05>123.10 123.05>75.10 219.05>95.10 164.10>95.10 164.10>109.10
Max Int. 476426 312530 254329 116808 67411 48785
CE 13 15 25 27 25 21
Product m/z 177.05>127.10 177.05>137.10 197.05>141.10 177.05>87.10 197.05>161.10 177.05>101.10
Max Int. 488117 165150 152666 103281 88909 79184
CE 17 17 13 25 7 27
Figure 2: Optimized Transitions for Two Pesticides Using the MRM Optimization Tool
Sheet1
Product m/z123.05>95.10219.05>123.10123.05>75.10219.05>95.10164.10>95.10164.10>109.10
Max Int.4764263125302543291168086741148785
CE131525272521
Sheet1
Product m/z123.05>95.10219.05>123.10123.05>75.10219.05>95.10164.10>95.10164.10>109.10
Max Int.4764263125302543291168086741148785
CE131525272521
Product m/z177.05>127.10177.05>137.10197.05>141.10177.05>87.10197.05>161.10177.05>101.10
Max Int.4881171651501526661032818890979184
CE17171325727
After adding the optimized transitions for the new pesticides to the existing Smart Pesticide Database, the MRM analysis method was created automatically. The program uses pesticide RIs in the database to accurately predict retention times for the target compounds. The Smart MRM function automatically adjusts Loop, Event, and Dwell times to optimize sensitivity for all compounds in the list simultaneously. Flexible MS events can create optimized methods with 400+ compounds. Used together, the Smart Pesticide Database and MRM Optimization Tool shortened the method development time from hours to just a few minutes.
Flexible MS events
method is created
Grab RTs from AART method
Figure 3: The MRM Analysis Method is Created Automatically and Optimized for Sensitivity
Experimental
ManualAutoManual operation Manual5+ hours (days?)30 minutes
AutoMRM Optimization Tool
AutoAuto
10 minutes15 minutes
Figure 4: Workflow using the MRM Optimization Tool
Experimental
ExperimentalInformation used to create the analysis method is shown below. It includes a compound table, retention indices and retention times, one transition with optimized CE for quantitation, and two reference transitions. Area ratios are also empirically determined, and can be used as part of the laboratory QAQC program.
Serial# Compound Name Ret. Index 1 Ret. TimeType m/z CE Ratio Type m/z CE Ratio Type m/z CE Ratio
1 Dichlorvos 1252 4.345 T 109.00>79.00 7 100.00 Ref.1 185.00>93.10 13 44.15 Ref.2 219.95>185.00 5 10.19
2 Mevinphos 1427 5.642 T 127.05>109.00 11 100.00 Ref.1 192.05>127.00 13 47.84 Ref.2 127.05>95.00 15 35.24
3 Etridiazole 1459 5.891 T 210.95>183.00 11 100.00 Ref.1 182.95>140.00 15 96.56 Ref.2 210.95>140.00 23 91.67
4 2-Phenylphenol 1533 6.483 T 169.10>141.10 13 100.00 Ref.1 169.10>115.10 25 91.99 Ref.2 170.10>141.10 23 86.39
5 Lindane 1779 8.660 T 180.95>145.00 15 100.00 Ref.1 218.90>183.00 9 66.47 Ref.2 218.90>145.00 19 33.83
6 Terbuthylazine 1782 8.694 T 229.10>173.10 7 100.00 Ref.1 214.10>71.10 19 78.34 Ref.2 214.10>132.10 9 59.36
7 Diazinone 1790 8.766 T 304.10>179.20 13 100.00 Ref.1 248.05>152.10 7 61.75 Ref.2 248.05>137.10 17 61.34
8 Tefluthrine 1816 9.002 T 177.05>127.10 17 100.00 Ref.1 177.05>137.10 17 33.83 Ref.2 197.05>141.10 13 31.28
9 Vinclozoline 1894 9.730 T 212.00>172.00 15 100.00 Ref.1 212.00>145.00 23 80.05 Ref.2 285.00>212.00 15 71.13
10 Transfluthrin 1903 9.815 T 163.05>127.10 7 100.00 Ref.1 163.05>91.10 15 82.75 Ref.2 163.05>143.00 17 75.80
11 Metalaxyl 1915 9.926 T 234.10>146.10 19 100.00 Ref.1 234.10>174.10 11 75.22 Ref.2 249.15>190.20 9 64.50
12 Pirimiphos methyl 1941 10.167 T 290.10>125.10 23 100.00 Ref.1 290.10>233.10 11 53.89 Ref.2 276.05>125.00 17 54.23
13 Malathion 1964 10.377 T 127.05>99.10 7 100.00 Ref.1 173.10>99.10 13 66.84 Ref.2 173.10>127.10 7 64.75
14 Chlorpyrifos 1980 10.529 T 313.95>257.80 19 100.00 Ref.1 315.95>259.90 19 74.59 Ref.2 285.95>257.90 9 47.29
15 Triadimefon 2003 10.738 T 208.05>111.10 23 100.00 Ref.1 208.05>127.10 15 89.54 Ref.2 210.05>183.10 9 43.88
16 MGK-264 2030 10.980 T 164.10>93.10 13 100.00 Ref.1 164.10>98.10 13 68.56 Ref.2 164.10>80.10 25 55.15
17 Penconazole 2063 11.283 T 248.10>157.10 25 100.00 Ref.1 159.00>123.10 19 50.14 Ref.2 248.10>192.10 15 45.77
18 Triadimenol 2092 11.541 T 168.15>70.00 9 100.00 Ref.1 128.00>65.10 23 38.42 Ref.2 112.05>58.10 11 27.68
19 Paclobutrazol 2132 11.899 T 236.05>125.10 11 100.00 Ref.1 236.05>167.10 9 37.10 Ref.2 238.05>127.10 11 32.42
20 Flutriafol 2155 12.104 T 123.05>95.10 13 100.00 Ref.1 219.05>123.10 15 65.60 Ref.2 123.05>75.10 25 53.38
21 Myclobutanil 2200 12.502 T 179.05>125.00 15 100.00 Ref.1 179.05>152.00 9 35.34 Ref.2 179.05>90.10 29 36.16
22 Bupirimate 2204 12.535 T 273.10>108.10 15 100.00 Ref.1 273.10>193.10 7 67.72 Ref.2 193.15>81.10 25 74.80
23 Endosulfan sulfate 2360 13.865 T 271.80>236.80 21 100.00 Ref.1 271.80>234.90 17 22.20 Ref.2 271.80>141.00 31 22.31
24 p,p'-DDT 2367 13.919 T 235.00>165.20 29 100.00 Ref.1 237.00>165.20 23 64.85 Ref.2 235.00>199.10 17 13.84
25 Tebuconazole 2399 14.184 T 250.10>125.10 19 100.00 Ref.1 250.10>70.10 9 40.63 Ref.2 252.10>127.10 23 35.38
26 Bifenthrin 2471 14.767 T 181.15>166.10 13 100.00 Ref.1 181.15>165.10 27 90.00 Ref.2 166.10>164.20 29 4.99
27 Phosalone 2556 15.432 T 182.05>111.00 15 100.00 Ref.1 182.05>75.10 27 53.27 Ref.2 182.05>138.00 9 38.67
28 lambda-Cyhalothrin 2597 15.748 T 197.05>141.10 11 100.00 Ref.1 208.10>181.10 7 97.01 Ref.2 197.05>161.10 7 54.32
29 Fenarimol 2631 16.001 T 251.00>139.00 15 100.00 Ref.1 251.00>111.10 29 42.14 Ref.2 330.05>139.10 9 34.45
30 Permethrin 2706 16.562 T 183.00>153.10 15 100.00 Ref.1 183.00>168.10 15 107.11 Ref.2 163.00>127.10 7 109.13
31 Cyfluthrin 2793 17.202 T 226.05>206.10 13 100.00 Ref.1 199.10>170.10 25 70.95 Ref.2 206.05>151.10 19 64.85
32 Etofenprox 2870 17.812 T 163.15>135.10 11 100.00 Ref.1 163.15>107.10 17 89.29 Ref.2 376.20>163.20 11 5.78
33 Flucythrinate 2876 17.860 T 199.10>157.10 9 100.00 Ref.1 199.10>107.10 23 94.17 Ref.2 225.10>119.10 19 18.37
34 Deltamethrin 3061 19.650 T 252.90>93.10 19 100.00 Ref.1 181.10>152.10 23 87.40 Ref.2 252.90>172.00 7 56.01
Ion1 Ion2 Ion3
Table 2: Results of MRM Optimization Used to Create the MRM Method
compound information
Cat. #Product Name:
31153QuEChERS Performance Standard A300 g/mL each in acetonitrile:acetic acid (99.9:0.1), 1 mL/ampul16 Compoundsrestek link
31154QuEChERS Performance Standard B300 g/mL each in acetonitrile:acetic acid (99.9:0.1), 1 mL/ampul7 Compoundsrestek link
31155QuEChERS Performance Standard C300 g/mL each in acetonitrile:acetic acid (99.9:0.1), 1 mL/ampul17 Compoundsrestek link
32567GC Multiresidue Pesticide Standard #5100 g/mL each in toluene, 1 mL/ampul34 Organonitrogen Compoundsrestek link
32568GC Multiresidue Pesticide Standard #6100 g/mL each in toluene, 1 mL/ampul18 Synthetic Pyrethroid Compoundsrestek link
vapor pressure at room temp.
aceton30.6 kPa
toluene2.9 kPa
acetinitrile9.7 kPa
http://www.restek.com/catalog/view/41957/32567http://www.restek.com/catalog/view/41958/32568http://www.restek.com/catalog/view/40505http://www.restek.com/catalog/view/40506http://www.restek.com/catalog/view/40507
compound category
nameret. Timem/zstandard mixtureCAS
Organonitrogen Compounds
Etridiazole (terrazole)5.874210.95>183.005Organonitrogen CompoundsONP2593-15-9
Terbuthylazine8.665229.10>173.105Organonitrogen CompoundsONP5915-41-3
Triadimefon10.716208.05>111.105Organonitrogen CompoundsONP43121-43-3
MGK-26410.964164.10>98.105Organonitrogen CompoundsONP113-48-4
Penconazole11.267159.00>123.105Organonitrogen CompoundsONP66246-88-6
Triadimenol (baytan)11.509112.05>58.105Organonitrogen CompoundsONP55219-65-3
Paclobutrazol11.872236.05>125.105Organonitrogen CompoundsONP76738-62-0
Flutriafol12.081219.05>123.105Organonitrogen CompoundsONP76674-21-0
Myclobutanil12.474179.00>152.005, COrganonitrogen CompoundsONP88671-89-0
Bupirimate12.513273.10>193.105Organonitrogen CompoundsONP41483-43-6
Tebuconazole (Folicur)14.16252.10>127.105Organonitrogen CompoundsONP107534-96-3
Fenarimol15.979330.05>139.105Organonitrogen CompoundsONP60168-88-9
Etofenprox17.816376.20>163.205Organonitrogen CompoundsONP80844-07-1
Synthetic Pyrethroid Compounds
Tefluthrin8.988177.05>127.106Synthetic Pyrethroid CompoundsSPP79538-32-2
Transfluthrin9.801163.05>143.006Synthetic Pyrethroid CompoundsSPP118712-89-3
Bifenthrin14.747181.00>166.106, CSynthetic Pyrethroid CompoundsSPP82657-04-3
lambda-Cyhalothrin15.731197.05>161.106Synthetic Pyrethroid CompoundsSPP91465-08-6
cis-Permethrin16.547163.00>127.106, CSynthetic Pyrethroid CompoundsSPP61949-76-6trans-permethrin 61949-77-7
Cyfluthrin17.202226.05>206.106Synthetic Pyrethroid CompoundsSPP68359-37-5
Flucythrinate17.834199.10>107.106Synthetic Pyrethroid CompoundsSPP70124-77-5
Deltamethrin19.63252.90>93.106, CSynthetic Pyrethroid CompoundsSPP52918-63-5
Organophosphorus Compounds
Mevinphos (phosdrin)5.636192.05>127.00AOrganophosphorus CompoundsOPP7786-34-7
Diazinon8.755304.10>179.20AOrganophosphorus CompoundsOPP333-41-5
Pirimiphos methyl10.152276.05>125.00AOrganophosphorus CompoundsOPP29232-93-7
Malathion10.358173.10>99.10AOrganophosphorus CompoundsOPP121-75-5
Chlorpyrifos10.518313.95>257.80AOrganophosphorus CompoundsOPP2921-88-2
Phosalone15.434182.05>75.10AOrganophosphorus CompoundsOPP2310-17-0
Organochlorines compounds
Dichlorvos (DDVP)4.311185.00>93.10AOrganochlorines compoundsOCP62-73-7
gamma-BHC (Lindane)8.643180.95>145.00BOrganochlorines compoundsOCP58-89-9
Endosulfan sulfate13.849271.80>236.80BOrganochlorines compoundsOCP1031-07-8
p,p'-DDT13.906235.00>165.20BOrganochlorines compoundsOCP50-29-3
Carbamates
Metalaxyl9.915234.10>146.10CCarbamates57837-19-1
others
2-Phenylphenol6.472170.10>141.10B90-43-7
Vinclozolin9.717285.00>212.00Cfungicide50471-44-8
table 2 in poster
Serial#Compound NameRet. Index 1Ret. TimeIon1Ion2Ion3Comment
Typem/zCERatioTypem/zCERatioTypem/zCERatio
1Dichlorvos12524.345T109.00>79.007100.00Ref.1185.00>93.101344.15Ref.2219.95>185.00510.19A
2Mevinphos14275.642T127.05>109.0011100.00Ref.1192.05>127.001347.84Ref.2127.05>95.001535.24A
3Etridiazole14595.891T210.95>183.0011100.00Ref.1182.95>140.001596.56Ref.2210.95>140.002391.675
42-Phenylphenol15336.483T169.10>141.1013100.00Ref.1169.10>115.102591.99Ref.2170.10>141.102386.39B
5Lindane17798.660T180.95>145.0015100.00Ref.1218.90>183.00966.47Ref.2218.90>145.001933.83B
6Terbuthylazine17828.694T229.10>173.107100.00Ref.1214.10>71.101978.34Ref.2214.10>132.10959.365
7Diazinone17908.766T304.10>179.2013100.00Ref.1248.05>152.10761.75Ref.2248.05>137.101761.34A
8Tefluthrine18169.002T177.05>127.1017100.00Ref.1177.05>137.101733.83Ref.2197.05>141.101331.286
9Vinclozoline18949.730T212.00>172.0015100.00Ref.1212.00>145.002380.05Ref.2285.00>212.001571.13C
10Transfluthrin19039.815T163.05>127.107100.00Ref.1163.05>91.101582.75Ref.2163.05>143.001775.806
11Metalaxyl19159.926T234.10>146.1019100.00Ref.1234.10>174.101175.22Ref.2249.15>190.20964.50C
12Pirimiphos methyl194110.167T290.10>125.1023100.00Ref.1290.10>233.101153.89Ref.2276.05>125.001754.23A
13Malathion196410.377T127.05>99.107100.00Ref.1173.10>99.101366.84Ref.2173.10>127.10764.75A
14Chlorpyrifos198010.529T313.95>257.8019100.00Ref.1315.95>259.901974.59Ref.2285.95>257.90947.29A
15Triadimefon200310.738T208.05>111.1023100.00Ref.1208.05>127.101589.54Ref.2210.05>183.10943.885
16MGK-264203010.980T164.10>93.1013100.00Ref.1164.10>98.101368.56Ref.2164.10>80.102555.155
17Penconazole206311.283T248.10>157.1025100.00Ref.1159.00>123.101950.14Ref.2248.10>192.101545.775
18Triadimenol209211.541T168.15>70.009100.00Ref.1128.00>65.102338.42Ref.2112.05>58.101127.685
19Paclobutrazol213211.899T236.05>125.1011100.00Ref.1236.05>167.10937.10Ref.2238.05>127.101132.425
20Flutriafol215512.104T123.05>95.1013100.00Ref.1219.05>123.101565.60Ref.2123.05>75.102553.385
21Myclobutanil220012.502T179.05>125.0015100.00Ref.1179.05>152.00935.34Ref.2179.05>90.102936.165
22Bupirimate220412.535T273.10>108.1015100.00Ref.1273.10>193.10767.72Ref.2193.15>81.102574.805
23Endosulfan sulfate236013.865T271.80>236.8021100.00Ref.1271.80>234.901722.20Ref.2271.80>141.003122.31B
24p,p'-DDT236713.919T235.00>165.2029100.00Ref.1237.00>165.202364.85Ref.2235.00>199.101713.84B
25Tebuconazole239914.184T250.10>125.1019100.00Ref.1250.10>70.10940.63Ref.2252.10>127.102335.385
26Bifenthrin247114.767T181.15>166.1013100.00Ref.1181.15>165.102790.00Ref.2166.10>164.20294.996
27Phosalone255615.432T182.05>111.0015100.00Ref.1182.05>75.102753.27Ref.2182.05>138.00938.67A
28lambda-Cyhalothrin259715.748T197.05>141.1011100.00Ref.1208.10>181.10797.01Ref.2197.05>161.10754.326
29Fenarimol263116.001T251.00>139.0015100.00Ref.1251.00>111.102942.14Ref.2330.05>139.10934.455
30Permethrin270616.562T183.00>153.1015100.00Ref.1183.00>168.1015107.11Ref.2163.00>127.107109.136
31Cyfluthrin279317.202T226.05>206.1013100.00Ref.1199.10>170.102570.95Ref.2206.05>151.101964.856
32Etofenprox287017.812T163.15>135.1011100.00Ref.1163.15>107.101789.29Ref.2376.20>163.20115.785
33Flucythrinate287617.860T199.10>157.109100.00Ref.1199.10>107.102394.17Ref.2225.10>119.101918.376
34Deltamethrin306119.650T252.90>93.1019100.00Ref.1181.10>152.102387.40Ref.2252.90>172.00756.016
1-200ppb cali with Matrix
original solution conc. (ppb)original solution volumn (uL)additional solvent volumn (uL)final solution volumn (uL)final solution conc. (ppb)
QuEChERS Performance Standard A & B & CGC Multiresidue Pesticide Standard #5 & 6
300,000
300,000151543545010,000solvent being acetonitril in QuEChERS Performance Standard A & B & C
100,000
100,000505045050010,000solvent being toluene in GC Multiresidue Pesticide Standard #5 & 6
10,000
10,00024241,1761,200200
10,000
200total Matix requied
10,00044180
Wang, Di: Wang, Di:dilution with matrix2002001,415
10,00022190200100
10,0001119520050
10,0001139540025
2008812016010
200441401605
200111952001
table 1 in poster
Organonitrogen CompoundsSynthetic Pyrethroid CompoundsOrganophosphorus Compounds
BupirimateBifenthrinChlorpyrifos
Etofenproxcis-PermethrinDiazinon
Etridiazole (terrazole)CyfluthrinMalathion
FenarimolDeltamethrinMevinphos (phosdrin)
FlutriafolFlucythrinatePhosalone
MGK-264lambda-CyhalothrinPirimiphos methyl
MyclobutanilTefluthrinCarbamates and others
PaclobutrazolTransfluthrinMetalaxyl
PenconazoleOrganochlorines compounds2-Phenylphenol
Tebuconazole (Folicur)Dichlorvos (DDVP)Vinclozolin
TerbuthylazineEndosulfan sulfate
Triadimefongamma-BHC (Lindane)
Triadimenol (baytan)p,p'-DDT
1-200ppb cali with standard
original solution conc. (ppb)original solution volumn (uL)additional solvent volumn (uL)final solution volumn (uL)final solution conc. (ppb)
300,000
300,000161,1841,2004,000solvent being acetonitril in QuEChERS Performance Standard A & B & C
100,000
100,000481,1521,2004,000solvent being toluene in GC Multiresidue Pesticide Standard #5 & 6
4,000
4,00025475500200
4,00012468480100
4,000647448050
4,000347748025
4,00062,3942,40010
4,00032,3972,4005
4,0002599,975100,0001
Analytical Conditions
Gas Chromatograph GC-2010 Plus
Injection Port 250 C1 L splitless injection, 1 minute sampling time
ColumnSH-Rxi-5Sil MS, 30 m x 0.25 mm x 0.25 m filmHelium carrier gasConstant Linear Velocity mode, 40.0 cm/second
Oven Program
85 C (hold 1 minute)25 C/minute to 160 C10 C/minute to 240 C10 C/minute to 290 C (hold 3 minutes)
Transfer Line 300 C
Mass Spectrometer GCMS-TQ8040
Acquisition Mode MRM
Ion Source 230 CElectron ionization mode, 70 eV
Collision Gas Argon, 200 kPa
MRM Loop Time Optimized with Smart MRM
Table 3: Optimized Instrument Conditions for Analysis of Pesticides in Hop Samples using the Shimadzu GCMS-TQ8040
Sample Preparation
QuEChERS Extraction Steps Followed by Cartridge SPE Cleanup
Results Calibration
A 5-point calibration curve was generated for all 34 target pesticides, covering the range from 1 to 200 parts-per-billion (ppb) (Figure 5). Figure 6 shows the overlaid MRM chromatograms from three transitions for two of the pesticides in the 1-ppb calibration standard.
Figure 5: Exponential Calibration Curves for Two Pesticides, 1 to 200 ppb
Terbuthylazine Lindane
Results Calibration
Figure 6: Example of Overlaid MRM Chromatograms for Two Pesticides in the 1-ppb Calibration Standard
Terbuthylazine Lindane
1 ppb 1 ppb
Results Sample RepeatabilityTwo different hops samples were processed using the QuEChERS procedure. The extracts were spiked with the pesticide mix at 25 ppb and analyzed in triplicate using the optimized MRM method. Chromatograms in Figure 7 illustrate how the MRM technique can be used to select the target compound from a complex matrix background, and produce reliable, reproducible results at low concentrations.
Myclobutanil
Citric Hops
Cascade Hops
Paclobutrazol Diazinone Bifenthrin
RSD 2.4%
RSD 2.7% RSD 1.3% RSD 3.3%
RSD 3.4% RSD 5.8%RSD 2.7%
RSD 0.5%
Figure 7: MRM Chromatograms of Two Hops Samples Spiked at 25 ppb and Analyzed in Triplicate
Summary and Conclusion
The data presented illustrate how a triple quadrupole GC-MS/MS operated in the MRM mode can be used to analyze for trace-level pesticide residues in complex plant matrices such as hops. The matrix was extracted using a QuEChERS kit, and interferences removed using an SPE cartridge. The resulting extracts were analyzed in triplicate using MRM transitions provided in the Smart Pesticide Database or individually optimized using the MRM Optimization Tool, with repeatability of 6% or better. The MRM method was fully optimized in just a few minutes, target compounds were selectively identified against the co-eluting matrix interferences, and quantitated at the parts-per-billion range.
AcknowledgementThe authors wish to acknowledge Restek Corporation, Bellefonte, PA for useful discussions and advice regarding column selection, standards, and providing the QuEChERS materials used in the development of this method.
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Screening for 34 Pesticides in Hops Using GC-MS/MSIntroductionIntroductionExperimentalSlide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Results CalibrationResults CalibrationResults Sample RepeatabilitySummary and ConclusionNeed More Info?