Selected ion storage versus tandem MS/MS for organochlorine pesticides determination in drinking waters with SPME and GC-MS

Abstract

The use of two modes for mass spectrometry (MS) detection with an ion trap instrument, selected ion storage (SIS) and tandem mass spectrometry (MS/MS), are compared for the solid-phase microextraction (SPME)–gas chromatography (GC) coupled to mass spectrometry (GC-MS) determination of 16 priority organochlorine pesticides (OCPs) in drinking water samples at the ultratrace levels (ng L⁻¹) required by official guidelines in the European legislation. Experimental parameters investigated for the SPME sample preparation were: the type of coating (100 µm polydimethylsiloxane, PDMS, and 65 µm poly(dimethylsiloxane)–divinylbenzene, PDMS/DVB), SPME modality, extraction and desorption times and desorption temperature and the methanol percentage in the SPME working solution. Under the calculated optimal conditions two methodologies were developed, one for SIS and the other for MS/MS modes. The detection limits, precision and accuracy were evaluated for both alternatives and were appropriate to the official guidelines requirements. The SPME–GC-MS(SIS) methodology offered LODs from 0.2–6.6 ng L⁻¹, precision below 13% and recoveries between 83 and 110%. The SPME–GC–MS/MS methodology provided limits of detection (LODs) ranging from 0.3 to 7.6 ng L⁻¹, % RSD were ≤14% and recoveries of 79–108% were achieved. After the results observed within an Interlaboratory Exercise, the latest MS methodology was selected for the pursued analysis in real drinking water samples. Also, the good results in this round-robin exercise validate the proposed SPME–GC–MS/MS methodology.

Keywords:

• OCPs
• drinking water samples
• DI–SPME
• GC–MS
• SIS
• MS/MS

Acknowledgement

Authors thank FYCIT (Asturias, Spain) for financial support under Project Ref. FC-06-PC-06-002.