Phenomenex roq QuEChERS Kits. Overview. Spinach Facts

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1 Optimisation of LC/MS Analysis of Pesticide Residues in Food Products When Using QuEChERS Technique Phenomenex roq QuEChERS Kits Aman Sharma Phenomenex ANZ 1 2 Background Overview Extraction & Cleanup using the QuEChERS approach LC/MS/MS Challenges and Optimisation Tips Spinach Facts Excellent source of vitamin C, vitamin K, iron, mineral! And pesticides! USDA found 48 pesticide residues found in spinach LC/MS/MS or GC/MS? 3 4

2 Multiresidue Pesticide Analysis in Fruits & Vegetables The QuEChERS Approach Life Before QuEChERS! Facilitated liquid Extraction Liquid Extraction of homogenized sample with ACN Matrix Removal by dspe Non-retentive SPE of ACN extract using a C18E cartridge LC/MS/MS Advantages GC/MS Organophosphorous Extraction by Aminopropyl SPE Organochlorines Extraction by Florisil SPE Carbamates Extraction by Aminopropyl SPE Relative fast, simple, easy to follow procedure Applicable to a variety of sample matrices COOK ET AL.: JOURNAL OF AOAC INTERNATIONAL VOL. 82, NO. 6, Reagents pre-packaged in ready-to-use kits 6 Sample Extraction dspe Cleanup Part 1: Liquid Extraction Add organic solvent + salts to extract target analytes Part 2: Dispersive SPE Supernatant is combined with loose sorbent INTERFERENCES ADHERE TO THE SORBENT Spin to pellet sorbent, decant and analyze supernatant Centrifuge to pellet homogenate 7 8

3 Spinach Extract dspe Extract SPE sorbents & salts pelleted Note: ~ 5 ml supernatant Matrix & salts pelleted Majority of pigments removed ~ 8-10 ml supernatant Split extract for LC/MS/MS & GC/MS Dark green in colour 9 10 LC/MS Challenges Different Mobile Phase Conditions Reconstitution LC/MS Solvent Exchange: 250 ul of extract reconstituted in 20% methanol in 5mM formic acid GC/MS Solvent Exchange: 4 ml of extracted reconstituted in toluene 11 12

4 LC/MS Challenges Mobile Phase / Sample Solvent Mismatch AOAC (2007) LC/MS Challenges - Peak Distortion 13 Early eluting peaks distorted with 25 % acetonitrile injection solvent (as suggested by AOAC) Peak splitting issue is resolved with reduced solvent strength 25 % MeOH 14 LC/MS Challenges - Sample Precipitation LC/MS/MS vs. GC/MS Advantages of LC/MS/MS: For polar & semi-polar compounds Better Peak Shape Higher Signal Intensity More selective & sensitive results Better linearity & %RSD Matrix components precipitate when 25 % methanol is used All filter membranes absorb analytes different for each filter Solution= centrifuge samples instead of filtering Also works better to add methanol first to dissolve residue, sonicate and then add 5mM Formic acid 15 16

5 LC/MS/MS vs. GC/MS LC/MS/MS vs. GC/MS LC/MS/MS provides better results for polar analytes GC/MS provides better results for non-polar compounds Take advantage of the ability to compare results using both analytical techniques Advantages of GC/MS: For non-polar compounds No solubility problems Phenomenex roq QuEChERS Kits

6 roq QuEChERS Resources Conclusions " The roq QuEChERS Brochure " The roq QuEChERS Users Guide QuEChERS provides a quick and easy approach to sample clean-up for a wide range of analytes from food and agriculture samples " The roq QuEChERS FAQ " Technical Note TN-0051 Pesticide Residues in Spinach " Technical Note With proper optimization, LC/MS provides reliable results and generally gives broader coverage of the many pesticides of interest than GC/MS LC/MS/MS & GC/MS both had their challenges, yet each technique provides high value to the overall multiresidue pesticide analysis TN-0052 Pesticide Residues in Lettuce " The roq QuEChERS Website " The Phenomenex Food Safety Web page " OUR NEW FOOD SAFETY SOLUTIONS GUIDE Extraction Salts of the AOAC Method Magnesium Sulfate Thank you! Drying agent to absorb water Induces phase separation with MeCN 400 mg per gram of sample References Sodium Acetate 1. S.J. Lehotay et al, J. Chromatogr A 2010, 1217, 16: S.J. Lehotay, J AOAC Int 2007, 90, 2: amans@phenomenex.com 23 Buffers sample for base sensitive compounds Buffering range ~ mg per gram of sample 24

7 SPE Sorbents for Spinach Matrix Removal Primary Secondary Amine (PSA) Removes organic acids, fatty acids, sugars, & anthocyanine pigments 50 mg per ml of extract, AOAC 25 mg per ml of extract, EN Analyte Recovery Graphitized Carbon Black (GCB) Removes chlorophyll & other pigments 50 mg per ml of extract 2.5 or 7.5 mg per ml of extract, EN 25 Recoveries of analytes within % with %RSD <15% Due to non-specific binding of GCB, thiabendazole & chlorothalonil did not meet passing criteria as expected 26 LC/MS/MS LC/MS/MS Peak Distortion Challenge 27 Early eluting peaks distorted with 25 % acetonitrile injection solvent (as suggested by AOAC) 28

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