Countering matrix effects in environmental liquid chromatography-electrospray ionization tandem mass spectrometry water analysis for endocrine disrupting chemicals

In recent years, despite the increasing success of liquid chromatography (LC) coupled to tandem mass spectrometry (MS), reports on matrix susceptibility have shown the limitations of the this powerful analytical technique. Matrix effects (MEs) result from co-eluting residual matrix components affecting the ionization efficiency of target analytes and can lead to erroneous results. The present work evaluates the matrix effect of environmental water samples on 35 endocrine disrupting chemicals (EDCs) in negative and positive LC-ESI-MS/MS. It was shown that mobile-phase additives could significantly influence matrix effects. Addition of acids resulted in a severe signal suppression (average ME%: <65%), and 1 mM ammonium formate increased the average ME% to 84%. The importance of an efficient sample clean-up and internal standardization also was demonstrated. Cleaner extracts resulted in reduced matrix effects (average ME%: 89%) and labeled internal standards proved to have a beneficial effect especially on signal reproducibility (average CV% 4.2% versus 2.6%). The results from the present work indicate that evaluation of matrix effects should become an integrated part of quantitative LC-ESI-MS/MS method development and validation. (C) 2004 Elsevier B.V. All rights reserved.