Solid-phase extraction of polar hydrophilic aromatic sulfonates followed by capillary zone electrophoresis–UV absorbance detection and ion-pair liquid chromatography–diode array UV detection and electrospray mass spectrometry

A comprehensive comparison of four different polymeric solid-phase extraction (SPE) materials for the extraction of 22 different aromatic sulfonates of environmental concern was performed. The investigated adsorbents were the polystyrene–divinylbenzene materials LiChrolut EN from Merck, Isolute ENV+ from International Sorbent Technology, HR-P from Macherey–Nagel and the new Oasis HLB poly(divinylbenzene-co-N-vinylpyrrolidone) copolymer from Waters. Different SPE parameters like the elution solvent and the drying step of the cartridges were optimized. Analyses were performed by capillary zone electrophoresis–UV absorbance detection (CZE–UV) and ion-pair liquid chromatography–diode array UV detection coupled in series with electrospray mass spectrometry (IP-LC–DAD-ESI-MS) in the negative ionization mode. LC–MS offers a higher separation efficiency than CZE. The best adsorbents were LiChrolut EN and HR-P followed by Isolute ENV+ and Oasis HLB. The recoveries for most of the onefold negatively charged aromatic sulfonates were >50% for the extraction from spiked ground water at 50 μg/l. Recoveries for LiChrolut EN and HR-P were approximately 20% higher than for Isolute ENV+. Very hydrophilic sulfonates containing more than one negative sulfonate group could not be extracted by any of the tested adsorbents.