The suitability of the new cleanup sorbent, Supel QuE Z-Sep+, has been successfully demonstrated for cleanup of beef kidney matrix. It was found to effectively reduce background without significantly reducing recovery of lipophilic pesticides such as organochlorines and some pyrethroids. GC-MS full-scan data indicated Z-Sep+ was found to provide better cleanup in the form of reduced background than PSA/C18, and less interference in the GC-MS/SIM analysis of the target pesticides themselves.
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.
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.
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.