Pesticides Screening in Drinking Water by 2D LC/QToF

Topics in Drinking Water
Oral Presentation

Prepared by C. Mallet1, J. Samuel2, S. Botch-Jones3
1 - Waters Corporation, 34 Maple St, Milford, MA, 01757, United States
2 - Boston University School of Medicine, Biomedical Forensic Sciences,, 72 E. Concord St, Boston, MA, 02118, United States
3 - Boston University School of Medicine, Biomedical Forensic Sciences, 72 E. Concord St., Boston, MA, 02118, United States


Contact Information: [email protected]; 508-482-3045


ABSTRACT

Many countries around the world have strict regulatory guide lines for drinking water quality. To satisfy legislative requirements, analytical methods have been developed to monitor a wide range of contaminants at trace levels using analytical techniques such as gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/tandem quadrupole mass spectrometry (LC/MS/MS).

Trace level analysis at ppt (part per trillion) constitute the bulk of the work load for the majority of testing laboratories worldwide. Current analytical techniques use a combination of extraction procedures, often requiring an enrichment process and accurate detection for any given target analyte. As such, large sample volumes are usually extracted using various manual extraction methods (ex: solid-phase extraction (SPE), liquid-liquid …etc) and are concentrated into a smaller volume. As an example, a typical extraction method usually starts with a 500 mL of sample and ending up with a final volume of a 100 uL (5 000: 1 enrichment ratio). If higher sensitivity is required, the only alternative left is to process larger sample volume, but will require an increase in time and manual labor.

In recent years, efforts are now being diverted to investigate effective screening methods with high resolution Time of Flight (ToF) instruments and with the capability of reaching sub ppb (part per billion) levels. With current single chromatography separation setup and the inherent low sensitivity of ToF instrument compared to tandem quadrupole MS, this demand is quite difficult to achieve. As such, a new analytical strategy is needed to reach those goals. This presentation will discuss the performance of 2D LC/QToF setup for the analysis of pesticides residues in drinking water at sub ppb level. With an enrichment factor of 20:1 from a rapid fractionation sample preparation protocol using two mixed mode sorbents, the gap between method and instrument limits of quantitation (LOQ) can be eliminated with large volume injection. Furthermore, by using an AT column dilution 2D LC configuration, 100 % organic solvent extracts can be injected directly, thus eliminating all evaporation and reconstitution steps from any sample preparation protocol.