Highly pigmented foods, such as spinach, require cleanup prior to analysis for pesticide residues. A dual-layer SPE tube containing graphitized carbon and aminopropyl on silica (NH2) is often used because; Carbon removes pigments and sterols and NH2 removes fatty acids, polar pigments, organic acids, and sugars. Removing these matrix materials reduces interferences that can lead to ion suppression in LC-MS, inlet contamination in GC-MS, and column contamination for both techniques.
Our Supel Sphere Carbon/NH2 SPE tube uses spherical materials for both the carbon and NH2 layers, providing fast, more consistent flows compared to tubes containing granular material. This allows gravity elution (instead of vacuum elution) to be applied to Supel Sphere tubes, resulting in more contact time between extracts and sorbents.
A group of 30 compounds was selected, representing pesticides, acaricides, insecticides, and fungicides. These samples were analyzed using Supel™ QuE QuEChERS and an Ascentis® Express RP-Amide HPLC Column.
An application was developed to demonstrate increased pigment removal for the analysis of pesticides, using Supel™ QuE Z-Sep/C18 QuEChERS and an Ascentis® Express C18 HPLC Column. The improved cleanup can decrease column and instrument fouling, leading to extended LC column lifetime and reduced instrument downtime.
QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) is a very popular method for the extraction and cleanup of fruit and vegetable samples for pesticide residue analysis.2-4 The extraction step uses acetonitrile and a salting out effect (with MgSO4). Cleanup is then accomplished using dispersive SPE (dSPE) followed by a centrifuge step prior to analysis.
This application shows the clean-up and analysis using Supel™ QuE Z-Sep+ QuEChERS and an SLB®-5ms GC column.
Food samples exhibit a challenge to analytical chemists to determine pesticide residues to meet food safety regulations in USA and EU. Therefore, more careful sample preparation is needed to successfully identify and quantify these compounds in food. Dikma offers SPE columns with different absorbent phases and QuEChERS method for sample pre-treament.