Headspace solid-phase microextraction of halogenated toluenes in environmental aqueous samples with polypropylene microporous membranes

Abstract

The optimization of the polypropylene microporous membrane based solid-phase microextraction (MMSPE) of several halogenated (Cl − and Br −) toluenes was carried out. The influence of several factors such as sampling mode, sample volume, stirring rate, ionic strength, exposure time, etc. on the performance of the microextraction process was thoroughly investigated. Under optimized conditions, analytes were concentrated onto a 2-cm long membrane exposed to the headspace (HS) of the sample vial containing 80 mL of water with a 30% of sodium chloride. Equilibrium was achieved after a sampling period of 1 h, at room temperature and vigorous magnetic stirring. After analytes desorption, with just 250 μL of n-hexane, they were determined by gas chromatography with micro-electron capture detection (GC-μ-ECD). The developed methodology was characterized and validated also by gas chromatography–mass spectrometry (GC–MS). The proposed approach presented good precision (RSDs of 6–15% and 2–8% under reproducibility and repeatability conditions, respectively) and linear responses ( R 2: 0.990–0.999) over more than two order of magnitude concentration ranges for di- to penta-substituted species either with GC–MS or GC-μ-ECD detection. The absolute extraction efficiency was directly related with the lipophilic nature of the studied species and their volatile character, ranging between 27% and 47% for di- to pentahalotoluenes. Despite being an adsorption based methodology, no matrix effects were observed for complex environmental water matrices such as river water or treated wastewater. The proposed approach provided a very simple and low-cost microextraction alternative rendering adequate limits of quantification, in the low/sub ng L −1 level, for environmental sample analysis of poly-halogenated toluenes.