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High-Throughput Multiresidue Pesticides Analysis by GC-MS/MS

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  • Proven and recommended, Rxi-5ms columns reliably separate pesticides with shared ion transitions.
  • Exceptionally stable, low-bleed column ensures accurate results at trace levels.
  • Pro EZGC chromatogram modeling software dramatically reduces method development time.

Using GC-MS/MS for multiresidue pesticides analysis makes it possible to analyze large numbers of pesticides at once due to the superior secondary separation of selected reaction monitoring (SRM). GC-MS/MS analysis also provides excellent sensitivity, allowing for limits of detection below 10 ppb, which is the typical maximum residue limit. However, comprehensive multiresidue pesticides methods still require reliable chromatographic separation of compounds that share ion transitions because those analytes cannot be distinguished by the MS/MS detector. Rxi-5ms columns contain an ideal stationary phase for this, one that reliably achieves essential chromatographic separations. In addition, these columns are ultra-low bleed, which can improve signal-to-noise ratios and mass spectral integrity. As shown in Figure 1, the combination of GC-MS/MS, and an Rxi-5ms column provides efficient separation, identification, and quantification of more than 200 pesticides. 

Figure 1: Analysis of 200+ Pesticides on an Rxi-5ms Column by GC-MS/MS

cgarm-img
GC_FS0609
PeakstR (min)Conc.
(µg/mL)
Mix
1.Allidochlor6.83104
2.Dichlobenil7.72103
3.Biphenyl8.24103
4.Mevinphos8.92109
5.3,4'-Dichloroaniline8.95103
6.Etridiazole9.31105
7.Pebulate9.37104
8.N-(2,4-Dimethylphenyl)formamide9.63104
9.Tetrahydrophthalimide9.64103
10.Methacrifos10.00108
11.Chloroneb10.10102
12.2-Phenylphenol10.17107
13.Pentachlorobenzene10.31102
14.Tecnazene11.42103
15.Propachlor11.51104
16.Diphenylamine11.63103
17.2,3,5,6-Tetrachloroaniline11.70103
18.Cycloate11.8104
19.Chlorpropham12.02107
20.Ethalfluralin12.18103
21.Trifluralin12.40103
22.Benfluralin12.45103
23.Sulfotepp12.49108
24.Phorate12.59109
25.Diallate 112.6104
26.BHC, alpha-12.70102
27.Diallate 212.8104
28.Hexachlorobenzene12.90102
29.Dicloran12.99103
30.Pentachloroanisole13.02102
31.Atrazine13.29105
32.BHC, beta-13.36102
33.Clomazone13.36104
34.BHC, gamma-13.52102
35.Terbutylazine13.64105
36.Quintozene13.65103
37.Terbufos13.66108
38.Pentachlorobenzonitrile13.69103
39.Fonofos13.73109
40.Propyzamide13.73104
41.Profluralin13.76103
42.Pyrimethanil13.85105
43.Diazinon13.97101
44.Disulfoton14.05109
45.Fluchloralin14.06103
46.BHC, delta-14.09102
47.Terbacil14.11105
48.Chlorothalonil14.21103
49.Tefluthrin14.23106
50.Isazophos14.27101
51.Triallate14.28104
52.Endosulfan ether14.55102
53.Pentachloroaniline14.64103
54.Propanil14.82104
55.Dimethachlor14.87104
56.Acetochlor15.03104
57.Methyl parathion15.06109
58.Vinclozolin15.06105
59.Chlorpyrifos-methyl15.07101
60.Tolclofos-methyl15.17108
61.Transfluthrin15.18106
62.Heptachlor15.25102
63.Alachlor15.26104
64.Propisochlor15.35104
65.Metalaxyl15.38107
66.Fenchlorphos15.41108
67.Fenitrothion15.72101
68.Pirimiphos-methyl15.76101
69.Prodiamine15.78103
70.Linuron15.79104
71.Pentachlorothioanisole15.83102
72.Dichlofluanid15.90103
73.Malathion15.96108
PeakstR (min)Conc.
(µg/mL)
Mix
74.Anthraquinone16.02106
75.Aldrin16.06102
76.Metolachlor16.1104
77.Fenthion16.15108
78.Chlorpyrifos16.21101
79.Parathion16.22109
80.Dichlorobenzophenone, 4,4'-16.26102
81.Triadimefon16.28105
82.Chlorthal-dimethyl16.33107
83.Fenson16.45102
84.MGK 264 116.56105
85.Bromophos-methyl16.60108
86.Diphenamid16.61104
87.Pirimiphos-ethyl16.71101
88.Isodrin16.72102
89.Cyprodinil16.77105
90.Isopropalin16.77103
91.MGK 264 216.82105
92.Chlorfenvinphos 116.87108
93.Metazachlor16.91104
94.Pendimethalin16.95103
95.Heptachlor epoxide16.97102
96.Penconazole16.97105
97.Chlozolinate17.05107
98.Tolylfluanid17.07103
99.Bromfenvinphos-methyl17.13108
100.Captan17.13105
101.Chlorfenvinphos 217.13108
102.Bioallethrin17.17106
103.Fipronil17.17105
104.Quinalphos17.21101
105.Triadimenol17.21105
106.Folpet17.28105
107.Procymidone17.34105
108.Chlorbenside17.37102
109.Triflumizole17.41105
110.Chlordane, trans-17.51102
111.Bromophos-ethyl17.58108
112.DDE, o,p'-17.62102
113.Paclobutrazol17.63105
114.Tetrachlorvinphos17.74108
115.Endosulfan I17.79102
116.Chlordane, cis-17.85102
117.Flutriafol17.90105
118.Nonachlor, trans-17.96102
119.Chlorfenson17.97102
120.Fenamiphos17.98108
121.Bromfenvinphos18.03108
122.Flutolanil18.07104
123.Iodofenfos18.10108
124.Prothiofos18.15108
125.Tricyclazole18.21105
126.Profenofos18.22108
127.Fludioxonil18.24105
128.Pretilachlor18.29104
129.DDE, p,p'-18.31102
130.Dieldrin18.37102
131.Oxadiazon18.4104
132.Myclobutanil18.46105
133.DDD, o,p'-18.50102
134.Oxyfluorfen18.51103
135.Flusilazole18.53105
136.Bupirimate18.59105
137.Nitrofen18.77103
138.Fluazifop-P-butyl18.84107
139.Endrin18.85102
140.Ethylan18.86102
141.Chlorfenapyr18.88105
142.Chlorthiophos 118.94108
143.Chlorobenzilate19.02107
144.Endosulfan II19.04102
145.Chlorthiophos 219.12108
146.DDD, p,p'-19.23102
PeakstR (min)Conc.
(µg/mL)
Mix
147.DDT, o,p'-19.31102
148.Ethion19.32108
149.Nonachlor, cis-19.33102
150.Chlorthiophos 319.40108
151.Endrin aldehyde19.45102
152.Sulprofos19.58108
153.Triazophos19.59109
154.Carbophenothion19.78108
155.4,4'-Methoxychlor olefin19.84102
156.Carfentrazone ethyl19.84107
157.Edifenphos19.88108
158.Norflurazon19.93104
159.Lenacil19.94105
160.Endosulfan sulfate19.97102
161.DDT, p,p'-20.04102
162.Hexazinone20.24105
163.2,4'-Methoxychlor20.27102
164.Tebuconazole20.31105
165.Propargite20.42105
166.Resmethrin 120.43106
167.Captafol20.48105
168.Piperonyl butoxide20.50109
169.Resmethrin 220.55106
170.Nitralin20.69103
171.Iprodione20.88105
172.Endrin ketone20.97102
173.Pyridaphenthion20.99101
174.Tetramethrin 121.00106
175.Phosmet21.06101
176.Bromopropylate21.12107
177.EPN21.14101
178.Tetramethrin 221.14106
179.Bifenthrin21.15106
180.Methoxychlor21.25104
181.Fenpropathrin21.3104
182.Tebufenpyrad21.37104
183.Phenothrin 121.59106
184.Tetradifon21.68102
185.Phenothrin 221.71106
186.Phosalone21.89101
187.Azinphos-methyl21.90101
188.Leptophos21.94108
189.Pyriproxyfen21.97105
190.Mirex22.16102
191.Cyhalothrin, lambda-22.30106
192.Fenarimol22.47105
193.Acrinathrin22.51106
194.Pyrazophos22.58101
195.Azinphos-ethyl22.63101
196.Pyraclofos22.73101
197.Permethrin, cis-23.14106
198.Permethrin, trans-23.29106
199.Pyridaben23.3104
200.Coumaphos23.40108
201.Fluquinconazole23.41104
202.Prochloraz23.48104
203.Cyfluthrin 123.83106
204.Cyfluthrin 223.93106
205.Cyfluthrin 324.02106
206.Cyfluthrin 424.06106
207.Cypermethrin 124.19106
208.Cypermethrin 224.30106
209.Cypermethrin 324.39106
210.Cypermethrin 424.43106
211.Flucythrinate 124.43106
212.Etofenprox24.53105
213.Acequinocyl24.54107
214.Flucythrinate 224.66106
215.Fluridone24.92105
216.Fenvalerate 125.25106
217.tau-Fluvalinate 125.47106
218.Fenvalerate 225.48106
219.tau-Fluvalinate 225.53106
220.Deltamethrin26.09106
ColumnRxi-5ms, 30 m, 0.25 mm ID, 0.25 µm (cat.# 13423)
Standard/SampleGC multiresidue pesticide standard #1 (cat.# 32563)
GC multiresidue pesticide standard #2 (cat.# 32564)
GC multiresidue pesticide standard #3 (cat.# 32565)
GC multiresidue pesticide standard #4 (cat.# 32566)
GC multiresidue pesticide standard #5 (cat.# 32567)
GC multiresidue pesticide standard #6 (cat.# 32568)
GC multiresidue pesticide standard #7 (cat.# 32569)
GC multiresidue pesticide standard #8 (cat.# 32570)
GC multiresidue pesticide standard #9 (cat.# 32571)
Diluent:Toluene
Conc.:10 µg/mL
Injection
Inj. Vol.:1 µL splitless (hold 0.5 min)
Liner:Topaz, single taper inlet liner w/wool, 4.0 mm x 6.5 x 78.5 (cat.# 23447)
Inj. Temp.:250 °C
Oven
Oven Temp.:90 °C (hold 1 min) to 330 °C at 8.5 °C/min (hold 5 min)
Carrier GasHe, constant flow
Flow Rate:1.4 mL/min
DetectorTSQ8000
SIM Program:50-550 m/z
Transfer Line Temp.:280 °C
Source Temp.:325 °C
Solvent Delay Time:5 min
Tune Type:PFTBA
Ionization Mode:EI
InstrumentThermo Trace GC
Sample PreparationIndividual standards were diluted with toluene to 10 ppm and analyzed in a short-cap, screw-thread vial (cat.# 21143) and capped with a short-cap, screw-vial closure (cat.# 24495).
NotesStandards were analyzed individually and were overlaid for this chromatogram.
Standards are also available as a kit: GC multiresidue pesticide standards kit (cat.# 32562).

 

Some of the most challenging pesticides are closely eluting isomers and other compounds that share ions or ion transitions (Table I). Poor separation can affect automated integration, which can skew results and require time-consuming manual integrations. Further, if these compounds coelute completely, then identification and quantitation become impossible by MS/MS. To demonstrate the resolving power of Rxi-5ms columns for multiresidue pesticides in disparate matrices, samples were prepared in brown rice flour and oranges as follows and then analyzed on a Thermo TRACE GC with a TSQ8000 detector.

Brown Rice Flour Extracts

Five grams of brown rice flour was mixed with 10 mL of water. After a 60 second vortex, the brown rice flour was fortified at 10 ng/g with all residues from the GC multiresidue pesticides kit (cat.# 32562). The fortified brown rice flour suspension was shaken for 30 minutes. Extraction was performed using 10 mL of acetonitrile and the original unbuffered Q-sep QuEChERS salts (cat.# 25848). After centrifugation, the supernatant was removed and further cleaned up with pre-filled Q-sep QuEChERS dSPE tubes containing 150 mg MgSO4, 50 mg PSA, and 50 mg C18-EC (cat.# 26125).

Orange Extracts

Ten grams of homogenized orange was fortified at 10 ng/g with all residues from the GC multiresidue pesticide kit (cat.# 32562), mixed with 10 mL acetonitrile and two steel ball bearings (1/16''), and shaken for 10 minutes. Q-sep QuEChERS extraction salts for EN 15662 (cat.# 25849) were added, and the sample was shaken for 1 minute. The sample was centrifuged for 5 minutes, and the supernatant was removed and further cleaned up with prefilled Q-sep QuEChERS dSPE tubes containing 150 mg MgSO4, 50 mg PSA, and 50 mg C18-EC (cat.# 26125).

As shown in Figure 2, the Rxi-5ms column provides excellent resolution of several difficult pesticides. While benfluralin and trifluralin can be separated by MS/MS using different transitions, chromatographic resolution is advantageous here because it allows a shared main ion (m/z 264) to be used (Figure 2A). This is also true for the cyfluthrins and cypermethrins, where baseline chromatographic separation between the two groups of isomers was achieved (Figure 2D). In the case of compounds that share the same ion transitions, the selectivity of the Rxi-5ms column provided excellent chromatographic resolution of 4,4’-DDD and 2,4’-DDT (Figure 2B), as well as the permethrins (Figure 2C) and BHC isomers (Figure 2E). 

Table I: SRM and Shared Ions for the Pesticides in Figure 2

Name

tR SRM 1 SRM 2 SRM 3 Main Ions
(shared in bold)
Prec. Prod. CE Prec. Prod. CE Prec. Prod. CE
Trifluralin 12.36 306 160 23 306 206 12 306 264 8 306, 264, 43
Benfluralin 12.42 292 160 20 292 206 12 292 264 8 292, 276, 264
4,4’-DDD 19.17 237 165 22 235 165 24 235 199 12 237, 235, 165
2,4’-DDT 19.25 237 165 22 235 165 21 265 199 16 237, 235, 165
cis-Permethrin 23.04 183 153 12 163 127 6 183 168 10 183, 165, 163,
trans-Permethrin 23.19 183 153 14 163 91 13 163 127 6 183, 165, 163,
Cyfluthrin 24.20* 226 206 10 163 91 14 163 127 6 226, 203, 163
Cypermethrin 24.55* 181 152 18 163 91 11 163 127 6 209, 181, 163
α-BHC 12.68 219 183 8 181 145 13 217 145 18 219, 217, 183, 181
β-BHC 13.34 219 183 8 181 109 27 181 145 15 219, 217, 183, 181
γ-BHC 13.49 219 183 8 181 109 29 181 145 13 219, 217, 183, 181
δ-BHC 14.06 219 183 8 181 109 28 181 145 13 219, 217, 183, 181


*The window for these transitions was one minute.
Prec – Precursor ion
Prod – Product ion
CE – Collision energy    

Figure 2: Selected Transitions of Isomers and Compounds Sharing Ions

A) Trifluralin and Benfluralin at 10 ppb in Brown Rice Flour Extract B) 4,4’-DDD and 2,4’-DDT at 10 ppb in Brown Rice Flour Extract C) Permethrins at 10 ppb in Brown Rice Flour Extract D) Cyfluthrins and Cypermethrins at 10 ppb in Orange Extract E) BHC Isomers at 10 ppb in Brown Rice Flour Extract

 

cgarm-img
GC_FS0610
PeakstR (min)Conc.
(ng/g)
Precursor IonProduct IonCollision EnergyMix
1.Trifluralin12.351030626483
2.Benfluralin12.431029226483
3.α-BHC12.7010181145132
4.β-BHC13.3310181145152
5.γ-BHC13.4910181145152
6.δ-BHC14.0510181145132
7.DDD, p,p'-19.1710235165242
8.DDT, o,p'-19.2510235165242
9.Permethrin, cis-23.0410183168106
10.Permethrin, trans-23.1910183153146
11.Cyfluthrins24.00-24.3510226206106
12.Cypermethrins24.35-24.701016312766
ColumnRxi-5ms, 30 m, 0.25 mm ID, 0.25 µm (cat.# 13423)
Standard/SampleGC multiresidue pesticide standards kit (cat.# 32562)
Diluent:Toluene
Injection
Inj. Vol.:1 µL splitless (hold 0.5 min)
Liner:Topaz, single taper inlet liner w/wool, 4.0 mm x 6.5 x 78.5 (cat.# 23447)
Inj. Temp.:250 °C
Oven
Oven Temp.:90 °C (hold 1 min) to 330 °C at 8.5 °C/min (hold 5 min)
Carrier GasHe, constant flow
Flow Rate:1.4 mL/min
DetectorTSQ8000
Transfer Line Temp.:280 °C
Source Temp.:325 °C
Solvent Delay Time:5 min
Tune Type:PFTBA
Ionization Mode:EI
InstrumentThermo Trace GC
Sample PreparationBrown Rice Extract (shown in A, B, C, and E): 5 g of brown rice flour was mixed with 10 mL of water. After a 60 second vortex, the brown rice flour was fortified at 10 ng/g with all residues from the GC multiresidue pesticides kit (cat.# 32562). The fortified brown rice flour suspension was shaken for 30 minutes. Extraction was performed using 10 mL of acetonitrile and the original unbuffered Q-sep QuEChERS salts (cat.# 25848). After centrifugation, the supernatant was removed and further cleaned up with pre-filled Q-sep QuEChERS dSPE tubes containing 150 mg MgSO4, 50 mg PSA, and 50 mg C18-EC (cat.# 26125).

Orange Extract (shown in D): 10 g of homogenized orange was fortified at 10 ng/g with all residues from the GC multiresidue pesticide kit (cat.# 32562), mixed with 10 mL acetonitrile and two steel ball bearings (1/16''), and shaken for 10 minutes. Q-sep QuEChERS extraction salts for EN 15662 (cat.# 25849) were added, and the sample was shaken for 1 minute. The sample was centrifuged for 5 minutes, and the supernatant was removed and further cleaned up with prefilled Q-sep QuEChERS dSPE tubes containing 150 mg MgSO4, 50 mg PSA, and 50 mg C18-EC (cat.# 26125).

The extracts were analyzed in a short-cap, screw-thread vial (cat.# 21143) and capped with a short-cap, screw-vial closure (cat.# 24495).

 

As demonstrated above, using an Rxi-5ms column together with GC-MS/MS is an effective combination in achieving high-quality qualitative and quantitative pesticides analysis. Critical separations are achieved through both the power of the MS/MS and—when ions or ion transitions are shared—through the high efficiency and chromatographic selectivity of the Rxi-5ms column. In addition to improving data accuracy, good chromatographic separation reduces manual integration, which saves time and allows increased sample throughput. Labs interested in additional time savings can also explore virtual method development and optimization using Restek’s Pro EZGC chromatogram modeling software (www.restek.com/EZGC). With this free online tool, methods for multiresidue pesticides analysis can be developed or modified in minutes on a computer instead of taking days of instrument time in the laboratory.

FSAR4268-UNV