Determination of organic pollutants in municipal reverse osmosis concentrate by electrospray ionization-quadrupole time-of-flight tandem mass spectrometry and photocalaytic degradation methods

Recently UV/TiO2 photocatalytic treatment for municipal reverse osmosis concentrate (ROC) has drawn increasing attention due to its high efficiency and low cost. We determined the organics in ROC samples by a combination of multiple analytical techniques: i.e. electrospray ionization-quadrupole time of flight (ESI-QToF), photocatalytic degradation method, total organic carbon (TOC) analysis, fluorescence spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy and gas chromatography/mass spectrometry (GC/MS). By these multiple techniques we were able to determine the total dissolved organic carbon (DOC) to be 24.50 ppm, which was composed of high molecular weight (MW) (> 2000 Da) natural organic matter (NOM) of 23.36 ppm (95.35%wt.) and low MW (< 2000 Da) fluorosurfactants of 1.08 ppm (4.41%), and pharmaceuticals & other organic compounds of 0.06 ppm (0.24%). Using ESI-QToF tandam mass spectrometry, molecular structures of 5 series of fluorosurfactants (63 compounds) and 9 phamaceuticals were elucidated. Conjugated compounds and sample color were monitored by UV-Vis spectroscopy. No volatile organic compounds (VOCs) were detected in the ROC samples by GC/MS. A combination of these 6 techniques provided a comprehensive method to depict the overall constituents of various organics in ROC. Quantitative estimation of organic compounds and structural determination of surfactants and pharmaceuticals in ROC were also investigated.