Solid phase extraction procedure of polar benzene- and naphthalenesulfonates in industrial effluents followed by unequivocal determination with ion pair chromatography/electrospray-mass spectrometry

Highly water soluble benzene- and naphthalenesulfonates are widely used in the chemical, pharmaceutical, tannery, paper, and textile industries. In this work, Isolute ENV+ polystyrene divinylbenzene sorbent was used for the enrichment of 14 benzene- and naphthalenesulfonates from industrial wastewaters. The elution step was performed by adding 1 mL of water containing ion-pair reagent (5 mM of triethylamine (TEA) and 5 mM of acetic acid at pH 6.5) and 9 mL of methanol at 1 mL/min, The most relevant contribution was the use of ion-pair liquid chromatography followed by an orthogonal electrospray interface coupled to mass spectrometry in the negative ionization mode with postcolumn addition at 0.2 mL/min of methanol in combination with a volatile substance (triethylamine) as an ion-pair reagent. [M-H](-) ion was the base peak using low fragmentor voltages of 80 V with the electrospray interface. Significant fragmentation of the quasimolecular [M-H]- ion occurs at high fragmentor voltage, producing [M-SO2H](-), [M-SO3H](-), and [SO3](.-) diagnostic ions. Collision-induced dissociation of the parent ions for the benzene- and naphthalenesulfonates studied gave the [SO3](.-) fragment ion common to sulfonated compounds. At high fragmentor voltages of 150 V, [M-SO3H](-) ion is more abundant and therefore has a larger peak than the [M-H](-) peaks for 1,5-naphthalene-disulfonate, 2,6-naphthalenedisulfonate, 1-hydroxy-3,6-naphthalenedisulfonate, 2-hydroxy-3,6-naphthalenedisulfonate, and 2-amino-1,5-naphthalenedisulfonate. Recoveries were higher than 70%, with relative standard deviations between 1.3 and 10.7% with the exception of two naphthalenesulfonate compounds that had recoveries between 26 and 41%. Limits of detection (signal-to-noise ratio, 3) ranging from 0.6 pg to 0.13 ng (0.03-6.48 mu g/L) were achieved when 150 mt of groundwater was processed. The aromatic sulfonates 3-nitrobenzene-sulfonate, 4-methylbenzenesulfonate, 4-chlorobenzenesulfonate, 1-hydroxy-4-naphthalenosulfonate, 1-amino-6-naphthalenosulfonate, 1-amino-7-naphthalenosulfonate, and 1-naphthalenesulfonate and the linear alkyl benzenesulfonates C-10-LAS and C-11-LAS were unequivocally identified and quantitatively determined in mu g/L, in wastewater samples from wastewater treatment plants and textile and tannery industries. 2-Naphthalenesulfonate was found as a major pollutant at mg/L concentration levels.