Application of QuEChERS based methodology for the analysis of pesticides in sediments
Résumé
The analysis of micropollutants present in sediments generally requires to carry out a complex protocol including several successive steps for sample extraction and purification. The most popular method, the extraction by pressurised fluid, is very efficient for extracting the target analytes but also for all the other potentially interfering components that might be present within the matrix. Moreover, this technique is relatively expensive since dedicated equipment is needed. The QuEChERS approach, developed initially for the analysis of pesticides in fruits and vegetables, can be regarded as an alternative technique to simplify this step. It is easy to handle, relatively cheap and with low solvent consumption. Therefore, this technique has been evaluated in this study for the analysis of pesticides in sediments. The priority pesticides and the substances candidate to integrate the Water Framework Directive (2000/60/EC) list of pollutants were considered. Since the purification step of the QuEChERS technique is not intended to remove all interferents from the sample matrix, the analysis was performed by gas chromatography followed by a selective detection using tandem mass spectrometry. A QuEChERS type method and purification protocol based on the approach generally carried out for fruits and vegetables was applied. Therefore, an extraction with vortex agitation using acetonitrile was performed followed by a purification step by dispersive solid phase extraction with sodium sulfate, C18 or PSA. Initial tests were carried out on dry sediments but addition of 10 to 20% of water (v/w) increased the recovery of most of the pesticides tested. With this approach, recoveries ranging from 80 to 120 % were obtained for most of tested compounds. Limit of quantification were determined around 10 ng/g with linearity range up to 500 ng/g. This protocol was tested on certified reference material which provided satisfying results in most cases. Overall, the QuEChERS based approach appeared suitable for the analysis of pesticides in sediments.