Pesticides in Cannabis

Transcription

1 LCMS-8040 Application Pesticides in Cannabis Jeff Dahl, 1 Julie Kowalski, 2 Jason Zitzer, 3 and Gordon Fagras 3 1 Shimadzu Scientific Instruments; Columbia, Maryland 2 Restek Corporation; Bellefonte, Pennsylvania 3 Trace Analytics; Spokane, Washington

2 Summary: An LC-MS method for detection of pesticides in cannabis with QuEChERS extraction was developed. Background: Medicinal and recreational use of cannabis has increased rapidly in recent years. Like other crops, cannabis is susceptible to insects, mold, and chemical residue contamination. Pesticides and antifungals have been applied to cannabis to increase yields however these substances may cause human harm if they are consumed by users. Sensitive and selective detection of these residues is necessary for consumer protection. QuEChERS extraction and LC-MS analysis offers effective and efficient detection of such chemical residues. fortification standards as appropriate. A multiresidue pesticide mix was used (Restek part number 31971). After hydration of the samples, 15 ml acetonitrile with 1% acetic acid was added to each followed by shaking for 30 minutes. To each sample was added the contents of an AOAC QuEChERS Packet (Restek part 26237) and the samples were vigorously mixed for 2 minutes and centrifuged. Dispersive SPE was used to clean up the sample extracts for LCMS analysis. Several formulations of cleanup reagents were tested for optimum combination of matrix removal and recovery. The best formulation was a combination of PSA, C18, Method: Cannabis samples were provided by licensed growers in Spokane, Washington, and samples were prepared and analyzed in a certified lab in that state. Pesticide-free organically-grown cannabis was used for spiking studies and calibration curves. A variety of cannabis samples offered for retail sale were analyzed for pesticides as well. Cannabis dried flower samples were homogenized by an automated grinder and weighed portions of grams were used for each analysis. Each ground sample was hydrated using 15 ml of 1% acetic acid in water and agitated for 30 minutes. Samples were spiked with internal standards and Figure 1: Moldy cannabis flower. The white powder is mold growth which can flourish in high humidity growing operations. Figure 2: Representative dried cannabis flower samples (anonymized) tested for pesticides. Page 2

3 Hydrate 15 ml 1% acetic acid vortex/shake 30 min 15 ml 1% acetic acid in ACN, vortex & shake 30 min Add AOAC QuEChERS salts, vortex & shake 2 min Grind g test portion Spin 2 min 3000 RCF, clean up 1 ml supernatant with dspe Figure 3: QuEChERS extraction of dried cannabis flower for pesticide analysis. (x100,000) min Figure 4: Representative chromatogram of pesticide mix spiked in cannabis matrix at an intermediate level (31 ppb) P200x28_75_J17L5-50_075.lcd Page 3

4 (x1,000) 140>94.00(+) 140>125.10(+) 7.5 Methamidophos (x1,000) 200>170(+) 200>135(+) 7.5 Thiabendazole (x10,000) >226.10(+) >124.00(+) 4.0 Diethofencarb (x10,000) >89.10(+) >46.00(+) Cycluron (x10,000) >109.00(+) >150(+) Promecarb (x10,000) >150(+) >194.05(+) Flufenacet (x10,000) >427.00(+) >188.10(+) Fluoxastrobin (x1,000) >267.10(+) >116.00(+) Kresoxym-methyl (x1,000) >187.00(+) >159.00(+) Zoxamide (x10,000) >147.00(+) >309.05(+) Pyridaben (x1,000) Myclobutanil (x10,000) Piperonyl Butoxide >70.10(+) >125(+) >177.00(+) >149.00(+) >119.10(+) P200x28_48_J17L5-U_048 Figure 5: Individual representative chromatograms for selected pesticides. and carbon in the ratio 50:50:7.5 in addition to MgSO4 (Restek part 26243). The supernatants were added to the dispersive SPE reagents, mixed vigorously, and centrifuged. The supernatants were removed and concentrated approximately 5-fold by evaporation prior to analysis. Each sample was centrifuged to remove particulates before being placed in an autosampler vial. LCMS analysis was carried out on a Shimadzu Prominence HPLC with LCMS-8040 triple quadrupole mass spectrometer. The LC column was a Restek Ultra-AQ C18 column (3 µm, mm) and a binary gradient was used of 5 mm ammonium formate with 0.1% formic acid (pump A) and methanol (pump B). The flow rate was ml/min, the column temperature was 40 C, and the total run time was 15 min. A divert valve was used to send the unretained and re-equilibration portion of the gradient to waste to reduce intstrument fouling and the injection volume was limited to 1 µl. Page 4

5 Methamidophos r 2 > Thiabendazole r 2 > Diethofencarb r 2 > Cycluron r 2 > Promecarb r 2 > Flufenacet r 2 > Fluoxastrobin r 2 > Kresoxym-methyl r 2 > Zoxamide r 2 > Pyridaben r 2 > Area Ratio Myclobutanil r 2 > Area Ratio(x100) Piperonyl Butoxide r 2 > P200x28.lcb Figure 6: Individual representative calibration curves for selected pesticides. Electrospray ionization in continuous polarity switching mode was used for detection. Optimized MRM settings were used for each compound and at least one quantifier and one qualifier transition was selected. The retention times were found and used to program the MRM segments for optimum duty cycle. Results and Discussion: A representative chromatogram of a prepared, spiked cannabis sample is shown in the figure. The total run time was 15 min. and chromatographic peaks were observed with good peak shape and retention time reproducibility. Individual chromatograms from selected pesticides are shown in the figure. The calibration curve was prepared in spiked matrix over the range of 3.91 to 500 ppb, as dried flower weight. Individual calibration curves for selected compounds are shown as well. The total recovery for each compound, as measured by comparing the peak area for a 50 ppb spiked sample with a spiked process blank, which represents 100% recovery and no matrix effects. Page 5

6 3-hydroxycarbofuran 19.5 Fenhexamid 126 Nitenpyram 19.6 Acephate 4.6 Fenobucarb 8.3 Novaluron 4.9 Acetamiprid 4.1 Fenoxycarb 10.6 Omethoate 4.5 Aldicarb 4.1 Fenpyroximate 1.3 Oxadixyl 5.4 Aldicarb Sulfoxide 17.8 Fenuron 4.3 Oxamyl 2.1 Aldoxycarb 4.3 Fipronil 9.7 Paclobutrazol 11.8 Aminocarb 2.1 Flonicamid 25.8 Penconazole 27.4 Azoxystrobin 4.5 Fluazinam 7.4 Picoxystrobin 1.1 Benalaxyl 2.6 Fludioxonil 38.5 Piperonyl Butoxide 1.2 Bendiocarb 4.3 Flufenacet Pirimicarb 2.1 Bifenazate 2.2 Fluometuron 8.6 Prochloraz 12.9 Bitertanol 13.4 Fluoxastrobin 5.1 Promecarb 9.9 Boscalid 52.8 Fluquinconazole 119 Prometon 19.1 Bromuconazole Isomer Flusilazole 6 Propamocarb 9.5 Bromuconazole Isomer Flutolanil Propargite 2.3 Bupirimate 199 Flutraifol 2 Propiconazole 70.6 Butafenacil Formetanate 2.4 Propoxur 2.1 Carbaryl 19.5 Fuberdiazole Pymetrozine 6.7 Carbendazim 5.7 Furalaxyl 2.3 Pyracarbolid 2.3 Carbetamide 2.2 Furathiocarb 1.2 Pyraclostrobin 10.2 Carbofuran 2.3 Hexaconazole 2 Pyridaben 1 Carboxin 4.7 Hexaflumuron 3.0 Pyriproxyfen 1.3 Carfentrazone-ethyl 45.3 Hexythiazox 11.2 Quinoxyfen 3.1 Chloantraniliprole 16.8 Imazalil 180 Rotenone 13.3 Chlorotoluron 4.8 Imidacloprid 33.7 Siduron 2 Chloroxuron 2.4 Indoxacarb 36.9 Spinetoram 6.1 Clethodim Isomer Ipconazole 23.2 Spinosad A 7.4 Clofentazine 51.3 Iprovalicarb 18.8 Spinosad D 12.3 Clothianidin 9.2 Isoprocarb 4.6 Spirotetramat 10.9 Cyazofamid 4.5 Isoproturon 2.6 Sulfentrazone 8.2 Cycluron 11.4 Kresoxym-methyl 10.9 Tebuconazole 5.5 Cyproconazole 6 Linuron 33.9 Tebufenozide 5.2 Cyromazine 90 Mandipropamid 7.7 Tebufenpyrad 6 Dicrotophos 9.1 Mefenacet 2.7 Tebuthiuron 1.1 Diethofencarb 2.4 Mepanipyrim 92.6 Temephos 24.5 Difenoconazole 6 Mepronil 31.6 Tetraconazole 2 Diflubenzuron 38.8 Metaflumizone 2.2 Thiacloprid 2.1 Dimethoate 4.4 Metalaxyl 4.1 Thiamethoxam 4.3 Dimethomorph 50.1 Metconazole 43.1 Thidiazuron 25.1 Dimoxystrobin 2.3 Methabenzthiazuron Thiobencarb 5.1 Diniconazole 41.3 Methamidophos 4.9 Thiophanate-methyl 4.9 Dinotefuran 4.4 Methiocarb 9.6 Triadimefon 33.6 Diuron 4.5 Methomyl 4.4 Triadimenol 8.9 Emamectin B1a 1.6 Methoprotryne 21.2 Trichlorfon 7.2 Epoxiconazole 40.1 Methoxyfenozide Tricyclazole 9.1 Eprinomectin 5.6 Metobromuron 15.5 Trifloxystrobin Ethiofencarb 9.1 Metribuzin 15.4 Triflumizole 2.8 Ethiprole 33.9 Mevinphos 18.2 Triflumuron 52.7 Etoxazole 1.3 Mexacarbate 4.2 Triticonazole 89.0 Fenamidone 10.1 Monocrotophos 181 Vamidothion 1.1 Fenarimol 125 Monolinuron 4.2 Zoxamide 10.3 Fenazaquin 1.4 Myclobutanil 9.0 Fenbuconazole 12.4 Neburon 150 Table 1: LCMS-8040 Compound list and estimated quantitation limits (ppb) on the basis of dried flower weight Page 6

7 3-hydroxycarbofuran 0.74 Fenobucarb 0.85 Neburon 0.41 Acephate 0.94 Fenoxycarb 0.75 Nitenpyram 0.88 Acetamiprid 0.87 Fenpyroximate 1.16 Novaluron 1.43 Aldicarb 0.83 Fenuron 0.74 Omethoate 0.96 Aldicarb Sulfoxide 2 Fipronil 0.93 Oxadixyl 0.67 Aldoxycarb 0.98 Flonicamid 0.91 Oxamyl 0.95 Aminocarb 0.86 Fluazinam 0.98 Paclobutrazol 0.67 Azoxystrobin 0.71 Fludioxonil 0.73 Penconazole 0 Benalaxyl 0.66 Flufenacet 0.70 Picoxystrobin 0.80 Bendiocarb 0.71 Fluometuron 0.65 Piperonyl Butoxide 0.82 Bifenazate 7.08 Fluoxastrobin 0.66 Pirimicarb 0.63 Bitertanol 0 Fluquinconazole 0.46 Prochloraz 7 Boscalid 2 Flusilazole 0.63 Promecarb 0.73 Bromuconazole Isomer Flutolanil 0.64 Prometon 0.34 Bromuconazole Isomer 2 4 Flutraifol 0.80 Propamocarb 0.75 Bupirimate 0.27 Formetanate 0.78 Propargite 7 Butafenacil 0.80 Fuberdiazole 0.44 Propiconazole 0 Carbaryl 5 Furalaxyl 0.67 Propoxur 0.75 Carbendazim 0.27 Furathiocarb 0.84 Pymetrozine 0.75 Carbetamide 0.84 Hexaconazole 0.84 Pyracarbolid 0.68 Carbofuran 9 Hexaflumuron 0.81 Pyraclostrobin 0.66 Carboxin 0.68 Hexythiazox 0.43 Pyridaben 0.27 Carfentrazone-ethyl 0.82 Imazalil 0.27 Pyriproxyfen 0.74 Chloantraniliprole 1 Imidacloprid 1.19 Quinoxyfen 0.49 Chlorotoluron 0.67 Indoxacarb 0.79 Rotenone 0.71 Chloroxuron 0.73 Ipconazole 0.76 Siduron 0.65 Clethodim Isomer Iprovalicarb 0.74 Spinetoram 9 Clofentazine 0.37 Isoprocarb 0.66 Spinosad A 0.47 Clothianidin 2 Isoproturon 9 Spinosad D 0.47 Cyazofamid 0.85 Kresoxym-methyl 0.64 Spirotetramat 0.81 Cycluron 2 Linuron 0.65 Sulfentrazone 4.74 Cyromazine 6 Mandipropamid 0.89 Tebuconazole 0.71 Dicrotophos 0.93 Mefenacet 9 Tebufenozide 0.72 Diethofencarb 0.94 Mepanipyrim 0.34 Tebuthiuron 0.71 Diflubenzuron 0.82 Mepronil 0.72 Temephos 0.84 Dimethoate 0.77 Metaflumizone 0.67 Tetraconazole 0.61 Dimethomorph 0.84 Metalaxyl 0.72 Thiacloprid 0.64 Dimoxystrobin 0.72 Metconazole 0.70 Thiamethoxam 8 Diniconazole 0.89 Methabenzthiazuron 0.65 Thidiazuron 0.43 Dinotefuran 3 Methamidophos 0.74 Thiobencarb 0.66 Diuron 0.64 Methiocarb 0.81 Thiophanate-methyl 0.68 Emamectin B1a 0.62 Methomyl 0.79 Triadimefon 0.79 Epoxiconazole 0.75 Methoprotryne 0.27 Triadimenol 0.89 Eprinomectin 1.30 Methoxyfenozide 0.81 Trichlorfon 1.64 Ethiofencarb 0.70 Metobromuron 0.65 Tricyclazole 4 Ethiprole 1.20 Metribuzin 0.63 Trifloxystrobin 0.75 Etoxazole 0.73 Mevinphos 0.81 Triflumizole 0.61 Fenamidone 0.86 Mexacarbate 0.60 Triflumuron 0.62 Fenazaquin 4 Monocrotophos 0.67 Triticonazole 2 Fenbuconazole 0.73 Monolinuron 0.62 Vamidothion 0.77 Fenhexamid 0.79 Myclobutanil 0.83 Zoxamide 0.71 Table 2: LCMS-8040 total recovery for each pesticide in dried flower matrix. Page 7

8 Total Recovery Total 25-50% 50-70% % >120% Table 3: Number of compounds by total recovery. Sample Code A B C D E F G H I J K L Pesticides detected 534 ppb Piperonyl butoxide 45 ppb Piperonyl butoxide 19 ppb Spinosad A, 21 ppb Spinosad D, 1.1 ppb Piperonyl butoxide 8.4 ppb Myclobutanil, 2.7 ppb Piperonyl butoxide 21 ppb Myclobutanil Table 4: Pesticides detected in commercially available cannabis samples presented for analysis. As can be seen, only a few compounds have recovery less than 50% or greater than 120%. One notable exception is bifenazate, which showed a strong matrix enhancement effect. This effect was confirmed by spiking experiments in a variety of cannabis specimens and should be considired whenever a signal for bifenazate is detected. Limits of quantitation were determined by measuring samples in triplicate at various levels. Signalto-noise of at least ten to one and RSD of 20% or better were required at the limit of quantitation. The limits of quantitation are reported in the table. A variety of cannabis samples offered for retail sale and presented to us for analysis were anonymized and measured for pesticide residues. The results are shown in the table. The most commonly detected pesticide was piperonyl butoxide, and was detected over a wide range of concentrations. Piperonyl butoxide finds wide use in pesticide formulations to enhance activity of the main ingredient. Myclobutanil, an antifungal known to be used in cannabis cultivation, was detected in a number of samples as well. Conclusion: An effective method for detection of pesticides in cannabis is demonstrated using QuEChERS sample extraction with dispersive SPE cleanup and LC-MS analysis with a triple quadrupole mass spectrometer. The method was applied to detect a number of pesticides in comercially available cannabis samples. Page 8

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