A fully automated analytical platform integrating water sampling-miniscale-liquid-liquid extraction-full evaporation dynamic headspace concentration-gas chromatography-mass spectrometry for the analysis of ultraviolet filters

Abstract

A fully automated analytical platform that seamlessly integrates online water sampling-sample preparation-gas chromatography-mass spectrometry (GC-MS) was developed for ultraviolet (UV) filters in this work. The online water sampling system consisted of a conventional sample vial (slightly modified to have both inlet and outlet ports), two tubings and a peristaltic pump, which controlled the water flow into and out of the vial. The sample preparation segment consists of miniscale liquid-liquid extraction (msLLE), coupled to full evaporation dynamic headspace concentration (FEDHS) on a commercial dual-arm autosampler. The extract from the msLLE step was subjected to a derivatization step, before being passed through a Tenax TA sorbent tube at the FEDHS stage. UV filters were used as model compounds in this work due to their potential endocrine and developmental toxicities, including benzhydrol, 2-ethylhexyl salicylate, homosalate, 2-hydroxy-4-methoxybenzophenone, 3-(4′-methylbenzylidene) camphor and benzophenone. The analytes (of which the first four underwent derivatization, by virtue of them possessing hydroxyl groups, but not the last two) were concentrated on the sorbent, and were thermally desorbed before being introduced to the GC-MS system for analysis. An orthogonal array design (OAD) strategy was employed to facilitate the optimization of the msLLE and derivatization factors while univariate optimization was performed for FEDHS. The optimized settings achieved low limits of detection (0.6–9.7 ng L−1) with good linearity (r2 ≥ 0.9926), and satisfactory absolute extraction recoveries (62.0%–80.7%) were obtained. The fully automated online water sampling-extraction/concentration-detection approach was demonstrated by applying it to the analysis of swimming pool water. Relative recoveries of the analytes in the pool water ranged from 85.4% to 118.2%. The described procedure has the potential to be a fully automated online water sampling-msLLE-FEDHS-GC-MS platform for the purpose of conducting routine onsite water analysis.