Centrifugal mini-SPE cleanup for monitoring contaminants in food. Part II: Sorbents capacity, quantification, and comparison of lots.

The goal of this study was to investigate cleanup and analytical performance of three different lots of a centrifugal mini-cartridge solid-phase extraction (mini-SPE) product. The study assessed the cleanup of QECh*All extracts from five food matrix types (liquid infant formula, orange, grains, catfish, and kale), followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis of 47 pesticides and contaminants spanning a LogP range of -1 to 8. A second lab used low-pressure (LP)GC- high-resolution (HR)MS with an orbital ion trap (orbitrap) instrument for quantification of the same samples and a separate assessment of sorbents capacity in cleanup. Cleanup of 125 mg equivalent sample in 0.5 mL extract was found to provide >90% more removal of common matrix background components (e.g. fatty acids, cholesterol) than when using more concentrated extracts. Monitoring more than a dozen matrix markers in final extracts within 5 ppm mass accuracy demonstrated that the degree of cleanup generally exceeded the dilution factor, which is an interesting and useful empirical finding for analysts using one-step SPE for cleanup. In GC-MS/MS, an analytical quality control standard (triphenylphosphate) exhibited an RSD of 4.8% (n = 83), while the internal standard (chlorpyrifos-d10) showed a recovery of 97 ± 5% (n = 45). Mean recoveries and RSDs for the targeted analytes were 98% and 8%, respectively, and matrix effects were within ±10% for nearly all analytes. No statistically consistent differences were observed among the three product lots, each containing 20 mg of anhydrous magnesium sulfate (MgSO₄) and 12 mg each of primary-secondary amine (PSA) and octadecylsilane (C18) sorbents. Degradation of labile pesticides, such as captan-d6, folpet(-d4), chlorothalonil, and ¹³C12-p,p'-DDT, was substantially reduced compared to other methods, with only partial degradation occurring in kale extracts. QECh*All with centrifugal mini-SPE cleanup was also demonstrated to achieve high-throughput in an easy procedure that an individual analyst followed to prepare 75 final extracts in <3 h.