Use of laminar cup liners for the preparation of fatty samples for pesticide analysis.

Residue analyses have been developed for hundreds of pesticides and their metabolites in foods. Normally, the fat is extracted with a non-polar solvent, followed by a re-extraction of the analytes into a polar solvent, removal of the remaining fat by several clean-up steps and finally determination by gas chromatography (GC). Over the last 3 years, experience has been gained in the use of laminar cup liners for GC injectors. The geometry of the laminar cup liner allows the injection of sample extracts with a residual fat content of tip to 5%. The cup prevents fatty compounds entering the capillary GC column. Using this approach, several residue methods can be simplified without losing precision or recovery. The preparation of the samples, such as cows milk, human milk, avocado and cosmetics can be reduced to one solvent extraction step with petroleum ether and one single cleanup step with an Extrelut column. No further clean up with Florisil or GPC is then necessary. The proposed method using a laminar cup and GC/ECD has been tested for the analysis of organochlorine and organophosphorous pesticides, PCBs, nitro-musk fragrances, together with pyrethroids and pyrethrins in the above matrices. Polycyclic musk substitutes were analysed by GC/MS.