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?