Separation and characterization of sulfonates in dissolved organic matter from industrial wastewater by solid phase extraction and high-resolution mass spectrometry

Electrospray ionization (ESI) source combined with high-resolution mass spectrometry (HRMS) has been successfully used to characterize the molecular composition of dissolved organic matter (DOM) in industrial wastewaters. However, sulfonates are commonly presenting in these wastewaters and showing strong ionization suppression for the ESI analysis, which seriously affects the characterization of other DOM components. In this paper, a novel method based on polymer anion exchange (PAX) solid phase extraction (SPE) was proposed to separate DOMs from petroleum refining and coal coking wastewaters into hydrophobic neutral, hydrophobic acids, and hydrophobic strong acids; the fractions were analyzed by negative-ion ESI Fourier transform ion cyclotron resonance mass spectrometry. The results show that PAX-SPE separated sulfonates from wastewaters and enabled the molecular characterization of oxygen-containing compounds, which are the major component of DOM in the wastewaters. Semi-quantitative analysis of sulfonates in the wastewaters was carried out and the results show that these compounds account for 11% and 2% in total organic carbon for the refinery and coal coking wastewaters, respectively. PAX-SPE with stepwise elution and followed by high-resolution mass spectrometry analysis enables a comprehensive characterization for the molecular composition of industrial wastewater DOM. The method has potential for extensive application and the results are instructive for the understanding of the molecular composition of DOM in industrial wastewaters.