Pesticide residue analysis of agricultural products has become commonplace in recent years. A popular approach to extraction of pesticides from fruit and vegetable samples involves the use of QuEChERS extraction followed by gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS) analysis. Highly pigmented samples such as spinach require more thorough cleanup prior to analysis for pesticide residues to avoid contaminating the analytical system. To clean these types of samples often involves the use of solid phase extraction (SPE) cartridges containing carbon in combination with aminopropylsilanized silica gel. Carbon has a strong affinity for planar molecules, and can remove pigments and sterols that are commonly present in many food and natural products. The aminopropyl (NH2) sorbent functions to remove organic acids, and will also retain some polar pigments and sugars. Sample processing is normally done using gravity, to allow for sufficient contact time between the elution solvent mix and the SPE materials in the cartridge. Many dual-layer cartridges currently available are made using granular materials. These materials have variations in particle size and shape, which can lead to slower and more inconsistent flow between cartridges. In this work, we evaluated a new dual-layer carbon/NH2 SPE cartridge containing spherical materials. Compared to SPE cartridges made with traditional granular materials, the new spherical materials were found to exhibit improved and more consistent flow characteristics. The new dual-layer SPE cartridge was evaluated with spinach extracts for color removal and pesticide recovery. The pesticides chosen for the study covered a variety of groups, and included polar and non-polar compounds. The new spherical materials were found to be highly effective at removing the chlorophyll present in the spinach extracts, and yielded better recoveries for a majority of the pesticides studied compared to granular materials.

Improved sample clean-up by new spherical materials in a dual-layer SPE tube for the analysis of pesticide residues in spinach

246th National Meeting (2013)

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