Use of solid-phase extraction, reverse osmosis and vacuum distillation for recovery of aromatic sulfonic acids from aquatic environment followed by their determination using liquid chromatography-electrospray ionization tandem mass spectrometry

Three different sample preparation techniques (i) solid-phase extraction, (ii) reverse osmosis and (iii) vacuum distillation have been investigated and the recoveries were compared for determination of highly water-soluble benzene and stilbene sulfonic acids in aqueous environment by liquid chromatography with photodiode array (PDA) and electrospray ionization tandem mass spectrometry (LC–ESI-MS/MS). The recoveries were quite high using vacuum distillation (>90%) compared to solid phase extraction and reverse osmosis. The negative ion ESI mass spectra containing the peaks of quasimolecular ion [M − H]− allow the molecular mass determination of unknown compounds whereas the structures were proposed using fragments obtained from MS/MS analysis of [M − H]− ions. At lower fragmentation voltages only the quasimolecular ion [M − H]− was observed and as fragmentation voltages increased, it led to the formation of fragment ions corresponding to [M − H–SO3]−, [M − H–SO2]−, and SO3−. The detection limits were 1–28 μg/L with LC–ESI-MS. The sample collected from wastewater treatment plant was found to contain 21.1, 13.3, 12.1, 41.8 and 9.9 μg/L of cis-4,4l-diaminostilbene-2,2l-disulfonic acid (cis-DASDA), trans-4,4l-diaminostilbene-2,2l-disulfonic acid (trans-DASDA), 3-amino acetanilide-4-sulfonic acid (3-AASA), 4-chloroaniline-2-sulfonic acid (4-CASA), 2-chloroaniline-5-sulfonic acid (2-CASA), respectively.