No abstract

In this work, the effects of matrix interferences on the analytical performance of a new multiresidue method based on off-line solid phase extraction followed by reversed-phase liquid chromatographic separation and electrospray triple quadrupole mass spectrometric detection were investigated. This technique allows the simultaneous determination of 30 triazines, phenylureas and chloroacetanilides, extracted from freshwaters, in 40 minutes. Quantifications were performed with the use of appropriate internal standards (i.e. atrazine D5, diuron D6 and metolachlor D6). The limits of quantification were from 1 to 32 ng L(-1) for the triazines, from 5 to 59 ng L(-1) for the phenylureas and from 13 to 54 ng L(-1) for the chloroacetanilides. The matrix effects were studied by spiking various waters (i.e. tap, river, pond and sea waters) with the chemicals of interest. The results showed that the samples with the highest conductivity (i.e. seawater) and the most abundant dissolved organic matter content (i.e. pond water) exhibited important matrix effects with signal suppressions and high imprecision, respectively. These matrix effects were strongly minimized by performing appropriate internal standardizations. Afterward, this analytical method was applied for analyzing environmental samples from either river or estuarine waters and for monitoring herbicide input in a freshwater-seawater interface.

Theoretical papers and environmental applications of hydrophilic interaction liquid chromatography (HILIC) have been published for a wide range of analytes, but to our knowledge, no study focused on acidic herbicides (e.g., triketones, phenoxy acids, sulfonylurea, and acidic metabolites of chloroacetanilides). Matrix effects are the main obstacle to natural sample analysis by liquid chromatography coupled with tandem mass spectrometry (MS) via an electrospray ionization (ESI) interface. Therefore, we paid particular attention on limiting interference by (i) adapting the emerging HILIC technique, which is generally considered more sensitive than conventional reversed phase liquid chromatography and (ii) optimizing the solid phase extraction (SPE) step using a design of experiment. A rapid and reliable off line SPE-HILIC-ESI-MS/MS method was thus developed for the quantification of acidic herbicides in fresh water, with limits of quantifications (LOQs) ranging from 5 to 22 ng L(-1). Then, the analysis of freshwater samples highlighted the robustness of the method, and the importance of the chloroacetanilides metabolites among the studied analytes.