Automated mini-column solid-phase extraction cleanup for high-throughput analysis of chemical contaminants in foods by low-pressure gas chromatography – tandem mass spectrometry

Authors: Lehotay, Steven; HAN, LIJUN - China Agricultural University; Sapozhnikova, Yelena

Submitted to: Chromatographia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2016
Publication Date: 6/13/2016
Citation: Lehotay, S.J., Han, L., Sapozhnikova, Y.V. 2016. Automated mini-column solid-phase extraction cleanup for high-throughput analysis of chemical contaminants in foods by low-pressure gas chromatography – tandem mass spectrometry. Chromatographia. 79:1113-1130. doi: 10.1007/s10337-016-3116-y.

Interpretive Summary: Analysis of pesticide residues and environmental contaminants in diverse food types is an important application for improved food safety and environmental health, and monitoring is routinely conducted in countless laboratories worldwide for many purposes. Higher sample throughput at lower costs using less labor for analysis of more residues with higher quality of results serves to better protect the consumer and environment, and adds value to the food commodity. This study evaluated and demonstrated how automation with new technology and streamlining of approaches to sample preparation and analysis enabled substantially higher sample throughput with fewer lab personnel and less instrument maintenance, while still receiving excellent results for many residues in diverse foods. The automated approach is especially useful for regulatory agencies, agrochemical companies, and contract monitoring labs, and it is expected to be widely used in the future to conduct improved monitoring analyses with higher sample throughput, lower cost, and less labor.

Technical Abstract: This study demonstrated the application of an automated high-throughput mini-cartridge solid-phase extraction (mini-SPE) cleanup for the rapid low-pressure gas chromatography – tandem mass spectrometry (LPGC-MS/MS) analysis of pesticides and environmental contaminants in QuEChERS extracts of foods. Cleanup efficiencies and breakthrough volumes using different mini-SPE sorbents were compared using avocado, salmon, pork loin, and kale as representative matrices. Optimum extract load volume was 300 uL for the 45 mg mini-cartridges containing 20/12/12/1 (w/w/w/w) anh. MgSO4/PSA (primary secondary amine)/C18/CarbonX sorbents used in the final method. In method validation to demonstrate high-throughput capabilities and performance results, 230 spiked extracts of 10 different foods (apple, kiwi, carrot, kale, orange, black olive, wheat grain, dried basil, pork, and salmon) underwent automated mini-SPE cleanup and analysis over the course of 5 days. In all, 325 analyses for 54 pesticides and 43 environmental contaminants were conducted using the 10 min LPGC-MS/MS method without changing the liner or retuning the instrument. Merely 1 mg equivalent sample injected achieved <5 ng/g limits of quantification. With the use of internal standards, method validation results showed that 91 of the 97 analytes achieved satisfactory results (70-120% recovery and RSD = 25%) in the 10 tested food matrices (n=160). Matrix effects were typically less than plus/minus 20%, mainly due to the use of analyte protectants, and minimal human review of software data processing was needed due to summation function integration of analyte peaks. This study demonstrated that the automated mini-SPE + LPGC-MS/MS method yielded accurate results in rugged, high-throughput operations with minimal labor and data review.