title: Development of an Automated Column Solid-Phase Extraction Cleanup of QuEChERS Extracts, Using a Zirconia-Based Sorbent, for Pesticide Residue Analyses by LC-MS/MS.
abstract: A new, automated, high-throughput, mini-column solid-phase extraction (c-SPE) cleanup method for QuEChERS extracts was developed, using a robotic X-Y-Z instrument autosampler, for analysis of pesticide residues in fruits and vegetables by LC-MS/MS. Removal of avocado matrix and recoveries of 263 pesticides and metabolites were studied, using various stationary phase mixtures, including zirconia-based sorbents, and elution with acetonitrile. These experiments allowed selection of a sorbent mixture consisting of zirconia, C18, and carbon-coated silica, that effectively retained avocado matrix but also retained 53 pesticides with <70% recoveries. Addition of MeOH to the elution solvent improved pesticide recoveries from zirconia, as did citrate ions in CEN QuEChERS extracts. Finally, formate buffer in acetonitrile/MeOH (1:1) was required to give >70% recoveries of all 263 pesticides. Analysis of avocado extracts by LC-Q-Orbitrap-MS showed that the method developed was removing >90% of di- and triacylglycerols. The method was validated for 269 pesticides (including homologues and metabolites) in avocado and citrus. Spike recoveries were within 70-120% and 20% RSD for 243 of these analytes in avocado and 254 in citrus, when calibrated against solvent-only standards, indicating effective matrix removal and minimal electrospray ionization suppression.
authors.affiliation: Food and Bioanalytical Division, R. J. Hill Laboratories, Private Bag 3205, Hamilton East, New Zealand.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Morris
authors.affiliation: Food and Bioanalytical Division, R. J. Hill Laboratories, Private Bag 3205, Hamilton East, New Zealand.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Schriner
mesh_terms: D000327:Adsorption; D002851:Chromatography, High Pressure Liquid; D002957:Citrus / Q000737:chemistry*; D005506:Food Contamination / Q000032:analysis*; D005638:Fruit / Q000737:chemistry; D027421:Persea / Q000737:chemistry*; D010573:Pesticide Residues / Q000737:chemistry / Q000302:isolation & purification*; D052616:Solid Phase Extraction / Q000295:instrumentation / Q000379:methods*; D053719:Tandem Mass Spectrometry; D015040:Zirconium / Q000737:chemistry
chemical_list: D010573:Pesticide Residues; D015040:Zirconium; C028541:zirconium oxide
keywords: ITSP; LC-MS/MS; QuEChERS; SPE; Z-Sep; avocado; citrus; multiresidue; pesticide; zirconia