Centrifugal mini-SPE cleanup for monitoring contaminants in food. Part I: Comparison with dispersive-SPE.

Solid-phase extraction (SPE) constitutes one of the most common techniques for cleanup of sample extracts in analytical chemistry. Traditionally, SPE cleanup involves 100-1000 mg of one sorbent phase housed in cartridges placed onto vacuum manifolds for manual performance of several steps. However, this format has several drawbacks regarding convenience, versatility, speed, cost, labor, and performance, among other facets. To overcome several of these limitations, dispersive (d)-SPE has become more commonly applied in which extracts are simply mixed with sorbents in a versatile, quick, easy, and cheap approach that often yields high recoveries of analytes. The main disadvantage of d-SPE, however, is that quality of cleanup is often sacrificed for its other benefits. Over time, other commercial SPE approaches and formats have become available, such as mini-column SPE (or µ-SPE) using either a robotic or centrifugal platform to avoid the inconveniences of traditional SPE with a vacuum manifold. In this way, the conveniences of d-SPE can be merged with the better cleanup of columnar SPE. In Part I of this study, a new commercial centrifugal mini-SPE product using different spin rates was compared with d-SPE in a SpinFiltr format. QECh*All (formerly known as QuEChERSER) extracts of 9 commodities (apple, orange, kale, grains, catfish, egg, infant formula, cashew, and coffee) were cleaned up at the same time using both techniques with the same sorbents from the same source with equivalent sample/sorbent ratios. Low-pressure gas chromatography - high-resolution mass spectrometry with orbital ion trap detection (LPGC-orbitrap) was used for analysis of 47 pesticides and environmental contaminants with LogP ranging from -1 to 8. Practical aspects, degree of cleanup, and analytical performance were compared. Centrifugal mini-SPE using 16-177 rcf was found to remove up to 99% of the fatty acids, cholesterol, phytosterols, and other matrix components from the extracts for the same or better sample throughput, cost, and ease compared to d-SPE. It also provided better and more consistent analyte recoveries, especially for the complex fatty matrices, except coffee which required more extensive cleanup than achieved by either approach.