Polyethersulfone solid-phase microextraction followed by liquid chromatography quadrupole time-of-flight mass spectrometry for benzotriazoles determination in water samples

A microextraction method for the determination of 1H-benzotriazole (BTri), and four polar derivatives (4 and 5-methyl-1H-benzotriazole, 4-TTri and 5-TTri; 5,6-dimethyl-1H-benzotriazole, XTri; and 5-chloro-1H-benzotriazole, 5-ClBTri), in surface and wastewater samples is presented. Analytes were pre-concentrated using a disposable, low cost polyethersulfone (PES) sorbent and further analysed by liquid chromatography quadrupole time-of-flight mass spectrometry (LC–QTOF-MS). Parameters affecting the efficiency of sample preparation (extraction conditions and desorption solvent) and those controlling the performance of LC–MS determination were investigated. Analytes were extracted from 15 mL water samples, containing a 30% (w/v) of sodium chloride (4.5 g) and adjusted at pH 4.5, using a tubular PES sorbent (5 cm length × 0.7 mm o.d., sorbent volume 42 μL). After methanol desorption and solvent exchange, benzotriazoles were determined by LC–MS, with chromatograms extracted using a mass window of 20 ppm, centred in their [M+H]+ ions. The identity of chromatographic peaks was confirmed with accurate ion product scan (MS/MS) spectra. The method provided limits of quantification (LOQs) between 0.005 and 0.100 μg L−1, and relative recoveries from 81% to 124% (except for XTri in sewage samples, ca. 60%) with associated standard deviations between 2% and 9%. When compared with polydimethylsiloxane covered stir-bars (coating volume 24 μL), the PES polymer achieved significant higher responses (5–20-fold) for these polar pollutants. BTri and tolyltriazoles (4-TTri and 5-TTri) were found in urban sewage and river water samples, affected by wastewater discharges, with the maximum concentration (5.9 μg L−1) corresponding to BTri in raw wastewater.