Quechers-Fast Simple Sample Prep for Multiresidue Pesticide

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Choosing a QuEChERS dSPE Sorbent
Primary and secondary amine exchange material (PSA) is the base sorbent used for QuEChERS dSPE cleanup of fruit and vegetable
extracts because it removes many organic acids and sugars that might act as instrumental interferences. In addition, C18 or graphi-
tized carbon black (GCB) may be used to remove lipids or pigments, respectively. Choice of sorbent should be based on matrix
composition and target analyte chemistry. Most methods make specific recommendations for acidic, basic, and planar pesticides,
which may require additional considerations.
As seen in Table II, GCB can have a negative effect on the recoveries of certain pesticides that can assume planar shapes (e.g. chlo-
rothalonil and thiabendazole). The work shown here was done with 50 mg GCB per mL extract, which emphasizes this effect. The
EN 15662 QuEChERS method recommends less GCB, which improves recoveries of planar pesticides, but still assures the removal
of pigments that can degrade GC-MS performance. To simplify and speed up sample prep, Restek QuEChERS tubes are available in
the sorbent combinations and amounts specified by EN 15662 and AOAC methods.
Sorbent Guide
Sorbent Removes
PSA* sugars, fatty acids, organic acids, anthocyanine pigments
C18 lipids, nonpolar interferences
GCB** pigments, sterols, nonpolar interferences
*PSA—primary and secondary amine exchange material
**GCB—graphitized carbon black
Table II: Select sorbents based on matrix and target analyte chemistry. (Percent recovery using C18 or GCB, relative to PSA alone).
Rt (min) pesticide CAS Number action/use classification C18* GCB**
9.50 dichlorvos 62-73-7 insecticide organophosphorus 111 116
9.67 methamidophos 10265-92-6 insecticide organophosphorus 105 107
11.75 mevinphos 7786-34-7 insecticide organophosphorus 112 130
12.02 o-phenylphenol 90-43-7 fungicide unclassified 106 97
12.14 acephate 30560-19-1 insecticide organophosphorus 128 147
13.89 omethoate 1113-02-6 insecticide organophosphorus 120 119
14.74 diazinon 333-41-5 insecticide organophosphorus 108 127
14.98 dimethoate 60-51-5 insecticide organophosphorus 124 151
15.69 chlorothalonil 1897-45-6 fungicide organochlorine 125 13
15.86 vinclozolin 50471-44-8 fungicide organochlorine 102 98
16.21 metalaxyl 57837-19-1 fungicide organonitrogen 105 117
16.28 carbaryl 63-25-2 insecticide carbamate 114 111
16.60 malathion 121-75-5 insecticide organophosphorus 124 160
16.67 dichlofluanid 1085-98-9 fungicide organohalogen 122 103
17.51 thiabendazole 148-79-8 fungicide organonitrogen 88 14
17.70 captan 133-06-2 fungicide organochlorine 88 91
17.76 folpet 133-07-3 fungicide organochlorine 108 63
18.23 imazalil 35554-44-0 fungicide organonitrogen 115 95
18.39 endrin 72-20-8 insecticide organochlorine 104 101
18.62 myclobutanil 88671-89-0 fungicide organonitrogen 119 114
19.07 4,4-DDT 50-29-3 insecticide organochlorine 102 95
19.22 fenhexamid 126833-17-8 fungicide organochlorine 118 77
19.40 propargite 1 2312-35-8 acaricide organosulfur 110 95
19.43 propargite 2 2312-35-8 acaricide organosulfur 121 114
19.75 bifenthrin 82657-04-3 insecticide pyrethroid 106 81
20.04 dicofol 115-32-2 acaricide organochlorine 98 54
20.05 iprodione 36734-19-7 fungicide organonitrogen 118 90
20.21 fenpropathrin 39515-41-8 insecticide pyrethroid 113 96
21.32 cis-permethrin 52645-53-1 insecticide pyrethroid 106 65
21.47 trans-permethrin 51877-74-8 insecticide pyrethroid 109 71
23.74 deltamethrin 52918-63-5 insecticide pyrethroid 97 52
*50 mg PSA, 50 mg C18, **50 mg PSA, 50 mg GCB % recovery = RRF C18 or GCB X 100
RRF PSA
Strawberry extracts were spiked at 200 ng/mL with pesticides and subjected to dSPE with PSA only. Results were used to generate single point calibration curves. Spiked extracts
were then subjected to additional dSPE sorbents (either C18 or GCB). Results are shown as percent recoveries relative to PSA alone.
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Optimize Analysis with Sorbent Choice