Analysis of N-Methylcarbamate Pesticides in Foods
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SHIMADZU APPLICATION NEWS LAAN-A-LC-E054 HIGH PERFORMANCE LIQUID CHROMATOGRAPHY No.L343 Analysis of N-Methylcarbamate Pesticides in Foods N-Methylcarbamate pesticides are widely used as phthalaldehyde (OPA) to produce fluorescent insecticides and herbicides, and residue analysis of derivatives, which are finally detected with high these chemicals in foods is conducted using post- sensitivity. column fluorescence derivatization HPLC. In this This Application News introduces an example of method, sodium hydroxide is added to the N- analysis of N-methylcarbamate pesticides in food methylcarbamates separated by an analytical column using the Prominence Carbamate Analytical System. to form methylamines, which are then reacted with o- Table 1 Analytical Conditions Separation of 10- N-Methylcarbamate Pesticides [Separation] Fig.1 shows the chromatogram obtained from analysis Column : Shim-pack FC-ODS (75 mmL. × 4.6mmI.D.) of a 10 µL injection of a standard mixture of ten Mobile Phase : A) Water B) Methanol methylcarbamate pesticides (aldicarb, ethiofencarb, Time Program : B.conc 14 % (0-4 min) → 40 % (10 min) → 45 % (17 min) oxamyl, carbaryl, fenobucarb, bendiocarb, methomyl, → → methiocarb, methiocarb sulfoxide, and 50 % (20-26 min) 14 % (26.01-35 min) methiocarb sulfone). Here, analysis was conducted Flow Rate : 1.0 mL/min using the analytical conditions shown in Table 1. Column Temp.: 50 ˚C Methiocarb sulfoxide and methiocarb sulfone are Injection Vol. : 10 µL metabolites (oxidants) of methiocarb so when [Detection ] detected are reported together with methiocarb to determine the total methiocarb in the original sample. Reagent 1 : 50 mmol/L NaOH Flow Rate : 0.5 mL/min Temperature : 100 ˚C Reagent 2 : 120 mmol/L Sodium borate buffer solution (pH9) containing 0.25 mmol/L OPA and 0.25 mmol/L 3-mercaptopropionic acid Flow Rate : 0.5 mL/min Temperature : 50 ˚C Detection : RF-10AXL (EX=340 nm, Em=445 nm) mV 2 I Peaks 60 1. Oxamyl 2. Methomyl 50 1 5 3. Methiocarb sulfoxide 4. Methiocarb sulfone 5. Aldicarb 40 7 6. Bendiocarb 3 7. Carbaryl 30 6 8 8. Ethiofencarb 4 9 9. Fenobucarb 10. Methiocarb 20 10 10 0 0.0 5.0 10.0 15.0 20.0 25.0 min Fig.1 Chromatogram of Standard Mixture of 10 N-Methylcarbamate Pesticides (0.5 mg/L each, 10 µL injection ) No.L343 Determination of N-Methylcarbamate Pesticides in Foods This system was applied to the analysis of peach and onion. Commercial peach and onion were prepared 1) mV according to the sample preparation procedure 20.0 shown in Fig.2, and 10 µL of each sample was injected. Fig.3 shows the analysis results. (Analytical 17.5 Peach conditions were the same as in Table 1.) 15.0 No pesticides were detected in either sample, so each 2 of the prepared solutions was spiked with a mixture of 12.5 5 10 N-methylcarbamate pesticides so that the 1 concentration of each was 0.1 mg/L. These analytical 10.0 3 7 results are shown in the upper chromatogram for each 6 8 sample. 7.5 4 9 10 5.0 Sample 20 g Acetone 200 mL 2.5 Homogenization (3 min) Filtration (Cerite) 0.0 Filtrate 1 Residue Acetone 100 mL 0.0 5.0 10.0 15.0 20.0 25.0 min Filtrate 1+2 Filtrate 2 Residue Evaporate under 40˚C (20 mL) mV 5 % Sodium chloride solution (200 mL) 20.0 Dichloromethane (100 mL) Mixing (5 min) 17.5 Onion Dichloromethane Layer 1 Water Layer Dichloromethane (100 mL) 15.0 2 Dichloromethane Layer 1+2 Dichloromethane Layer 2 Water Layer 12.5 5 1 Anhydrous sodium sulfate (10 g) ✽ Filtration (No.5) Washed with dichloromethane (50 mL), 3 times 10.0 3 7 Evaporate under 40˚C (1 mL) 6 8 n-Hexane (25 mL) 7.5 4 9 Acetonitrile saturated with n-hexane (30 mL) 10 Mixing (10 min) 5.0 Acetonitrile Layer 1 Hexane Layer 2.5 Acetonitrile saturated with n-hexane (30 mL) 0.0 Acetonitrile Layer 1+2 Acetonitrile Layer 2 Hexane Layer Acetonitrile saturated with n-hexane (30 mL) -2.5 25.0 Acetonitrile Layer 1+2+3 Acetonitrile Layer 3 Hexane Layer 0.0 5.0 10.0 15.0 20.0 min n-Hexane saturated with acetonitrile (50 mL) Mixing (5min) I Peaks Acetonitrile Layer Hexane Layer 1. Oxamyl 6. Bendiocarb Evaporate under 40 ˚C 2. Methomyl 7. Carbaryl Methanol (2 mL) Sample solution (0.3 mL) 3. Methiocarb sulfoxide 8. Ethiofencarb 0.001 mol/L Diluted hydrochloric acid (2.7 mL) 4. Methiocarb sulfone 9. Fenobucarb Filtration (0.45 µm) 5. Aldicarb 10. Methiocarb HPLC 10 µL injection Fig.2 Sample Preparation Fig.3 Chromatograms of Peach and Onion Upper: Sample (Spiked with pesticides, 0.1 mg/L each) Lower: Sample References 1) “Test Methods for Residual Pesticides in Food, and Additives in Animal Feed or Veterinary Products” (July 28, 2006 Ministry of Health, Labour and Welfare, Food Safety Supplement No. 0728004, July 28, 2006 Partial Revision, Japan) NOTES: ✽This Application News has been produced and edited using information that was available when the data was acquired for each article. This Application News is subject to revision without prior notice. SHIMADZU CORPORATION. International Marketing Division 3. 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