Development of an Analytical Method of Organochlorine Pesticide Residues in Bivalves from Oualidia in Morocco

Abstract

The preparation of samples for the analysis of persistent organic pollutants in bivalves in general and mussels in particular requires complex extraction methods for which it is often necessary to resort to several compelling preparation steps to be carried out. The QUEChERS method (Quick, Easy, Cheap, Effective, Rugged and Safe) is a softer alternative method than conventional extractions / purifications and leads to a less demanding implementation, as well as the use of less solvent. This preparation technique was adapted and evaluated for multiresidue analysis of organochlorine pesticides in mussel bivaves by gas chromatography coupled with tandem mass spectrometry (GC-MS / MS). The method was developed in two stages. In the first place, an optimization of the extraction step the extract is put in the freezer overnight complete to reduce the majority of the fat the second step was the optimization of the purification step. Different adsorbents were tested in direct or dispersed solid phase extraction mode. It emerges from this study that the best results were obtained by extraction with acetonitrile followed by a freezing step and finally purification by a mixture of adsorbents (MgSO4 LC-18 PSA). In addition, to demonstrate that the method is reliable, different validation parameters have been studied: linearity, quantification limit, recovery rates and selectivity. The results showed that, thanks to the changes introduced, it was possible to obtain a more selective method that improves the accuracy of about 13 organochlorine pesticides selected from the original method. It has been found that the method is suitable for the analysis of 13 POCs. In addition, with the developed method, recoveries between 70 and 120% and a relative standard deviation (RSDs) less than 20% were found.