Multiresidue Screening of Agricultural Chemicals in a Food Matrix using Varian SPE and Triple Quadrupole LC-MS/MS

Transcription

1 Multiresidue Screening of Agricultural Chemicals in a Food Matrix using Varian SPE and Triple Quadrupole LC-MS/MS Eugene Chang, Anita DerMartirosian, Guang Li, Nigel Simpson, and Ritu Arora Varian, Inc. Lake Forest, CA Marcus Kim Varian Canada According to Japanese Ministry of Agriculture, Forestry and Fishery Government data, Japan's domestic production supplies 40% of foods consumed, based on calorie supply. 60% of foods consumed is imported. Japan can no longer support its people's diet without imported foodf On May 29, 2006, Japan s s Ministry of Health, Labour, and Welfare (MHLW), equivalent to the FDA, introduced the positives list for detection of agricultural chemicals in foods. The legislation prohibited distribution of foods that contained these chemicals above a certain level of maximum residue limits (MRLs( MRLs). The agricultural chemicals include pesticides, feed additives, and veterinary drugs. The regulations apply to all domestically produced and imported foodstuffs and comprise a listing of almost 800 chemicals

2 A uniform level of 0.01 ppm was established as the level having no potential to cause damage to human health The regulation requires that analysts apply a set of testing protocols that use classic cartridge-based SPE and LC/MS or GC/MS techniques This talk will present data on a mix of 67 neutral, basic, and acidic chemicals analyzed by two different methods, both employing SPE and LC/MS/MS The previous system allowed for a very limited list of compounds for use as pesticides and veterinary drugs, only 283 substances, and set a zero tolerance for compounds not specified by the government of Japan

3 The uniform limit has been set at 0.01 ppm so that the estimated intake of agricultural chemicals does not exceed 1.5 µg/day when calculated based on the food consumption of Japanese population. In January 2005 the European Union (EU), established their uniform level at 0.01 ppm i.agricultural chemicals and their decomposition products which are determined not to pose adverse health effects ii.specified agricultural chemicals for which registration withholding limits are not established iii.agricultural chemicals which are determined not to require any MRL in foreign countries and whose uses are not restricted.

4 Experimental Step 1: Liquid-liquid extraction for Methods I & II For fruits, vegetables and herbs, weigh out 20.0 g of the sample. For tea and hops, weigh out 5.00 g of the sample and let stand in 20 ml of water for 15 minutes Add 50 ml of acetonitrile and homogenize the sample. Filter the sample by suction. Add 20 ml of acetonitrile to the residue on the filter paper. Perform homogenization and suction filtration. Mix both filtrates. Add acetonitrile to the filtrate to make a 100 ml solution

5 Add 50 ml of acetonitrile and homogenize the sample. Filter the sample by suction. Add 20 ml of acetonitrile to the residue on the filter paper. Perform homogenization and suction filtration. Mix both filtrates. Add acetonitrile to the filtrate to make a 100 ml solution Method I Measure out 20 ml of the extracted solution. Add 10 g of sodium chloride and 20 ml of 0.5 mol/l phosphate buffer (ph 7.0) and shake. Let stand until the solution is clearly separated into layers. Discard the aqueous layer. Dry the acetonitrile layer over sodium sulfate (anhydrous) and filter Method II Measure 20 ml of the extracted solution. Add 10 g of sodium chloride and 20 ml of 0.01 mol/l hydrogen chloride and shake. Let stand until the solution is clearly separated into layers. Discard the aqueous layer. Dry the acetonitrile layer over sodium sulfate (anhydrous) and filter Concentrate the filtrate to dryness at 40 C or lower. Dissolve the residue in 2 ml of acetonitrile toluene (3:1) Concentrate the filtrate to dryness at 40 C or lower. Dissolve the residue in 2 ml of acetone/triethylamine/n-hexane (20:0.5:80) Method I Condition a graphite carbon/ aminopropylsilanized silica gel layered mini column (500 mg/500mg) with 10 ml of acetonitrile/ toluene (3:1) (Bond Elut Carbon/NH2, 500 mg/500mg, 6 ml). Apply the solution obtained from the Extraction step to the column and elute the column with 20 ml of acetonitrile/ toluene (3:1) Collect the entire volume of effluent. Concentrate the effluent to 1 ml or less at 40 C or lower. Add 10 ml of acetone and concentrate to 1 ml or less at 40 C or lower. Add 5 ml of acetone to the concentrated solution and concentrate to dryness Step 2: Clean-up with Bond Elut Carbon/NH2 (Method I) and Bond Elut Silica (Method II) Method II Condition a silica gel mini column (500 mg) with 5 ml of methanol, 5 ml of acetone, and 10 ml of n-hexane in this order (Bond Elut Si, 500 mg, 10 ml). Apply the solution obtained from the Extraction step to the column Elute the column with 10 ml of acetone/triethylamine/n-hexane (20:0.5:80), and discard the effluent Elute the column with 20 ml of acetone/methanol (1:1). Collect the entire volume of effluent Dissolve the residue in methanol to make a 4 ml solution. Use this as the test solution Concentrate the effluent to dryness at 40 C or lower. Dissolve the residue in methanol to make a 4 ml solution. Use this as the test solution.

6 Method I: MS-MS transition details

7 Method I: MS-MS transition details Method II: MS-MS transition details

8 LC/MS/MS Analysis of Multiresidue Methods I and II on Pursuit XRs C18 and Pursuit C18 on 320 LCMS Method I: Chromatograms of 42 compounds in Tomato at 100 ppb -ve -ve -ve

9 Method II: Chromatograms of 25 compounds in Lemon at 100 ppb Method I: Compounds in Standard and Spiked Matrices (Tomato and Lemon), Quantitation

10 Method II: Compounds in Standard and Spiked Matrices (Tomato and Lemon), Quantitation S/N Ratio and Ion Ratio Identification Two fragment ions were monitored for each analyte for identification / confirmation. At 10 ppb levels, two fragment ions of Azinphos-methyl and Imazaquin show good signal to noise The ion ratios of daughter ion1 and ion2 of these compounds were used to help identify these compounds

11 Modifications made from Positive List procedure Method I: changed drying gas temperature from 400 C to 220 C Method II: changed drying gas temperature from 400 C to 250 C Column temperature: Method I switched from 40 C to ambient for tridimorph isomers as separation was better at ambient Linearity

12 Average Recoveries of Method I Compounds in Tomato spiked at 10 ppb and100 ppb levels (n=3) Average Recoveries of Method I Compounds in Tomato spiked at 10 ppb and100 ppb levels (n=3)

13 Average Recoveries of Method II Compounds in Tomato spiked at 10 ppb and100 ppb levels (n=3) Conclusions All 67 compounds included in Multiresidue Methods I and II can be analyzed by using cartridge-based SPE and LC/MS/MS. The products developed include the following: Method I: Bond Elut Carbon /NH2 layered cartridge offering hydrophobic and anion exchange properties Pursuit XRs C18 columns developed on a high surface area, 100Å, ultra-pure silica support 320 LC-MS/MS triple quadrupole Method II: Bond Elut Silica Pursuit C-18 columns based on 100Å, ultra-pure silica support 320 LC-MS/MS triple quadrupole Good linearity from 10 ppb to 400 ppb was observed for most analytes with r2 greater than Recoveries for most analytes in both methods were in the range of 60%-140%. These recoveries are within the EU and CDFA requirements Slight modifications were made to the drying gas temperature and column temperature compared to the existing Positive List procedure in order to see stable daughter ions and isomers

14 Acknowledgements Eugene Chang Anita DerMartirosian Guang Li Nigel Simpson Ritu Arora Thank you for your attention Japan Positive List - Analytical Methods used Multi-residue method for agricultural chemicals by GC/MS (agricultural products) Analytical methods for residual compositional substrates of agricultural chemicals, food additives and veterinary drugs in food Multi-residue method I for agricultural chemicals by LC/MS (agricultural products) Multi-residue method II for agricultural chemicals by LC/MS (agricultural products) Multi-residue method for agricultural chemicals by GC/MS (animal and fishery products) Multi-residue method I for Veterinary drugs, etc by HPLC (animal and fishery products) Multi-residue method II for Veterinary drugs, etc by HPLC (animal and fishery products) Return

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17 Method I: Chromatograms of 42 compounds in Tomato at 100 ppb -ve -ve -ve Return Return