New procedure for the control of the treatment of industrial effluents to remove volatile organosulfur compounds

We present a new procedure for the determination of volatile organosulfur compounds in samples of industrial effluents using dispersive liquid-liquid microextraction and gas chromatography with flame photometric detection. Initially, the extraction parameters were optimized. These included: type and volume of extraction solvent, volume of disperser solvent, salting out effect, pH, time and speed of centrifugation as well as extraction time. The procedure was validated for 30 compounds. The developed procedure has low detection limits of 0.0071-0.49 mu g/L and a good precision (relative standard deviation values of 1.2-5.0 and 0.6-4.1% at concentrations of 1 and 10 mu g/L, respectively). The procedure was used to determine the content of volatile organosulfur compounds in samples of effluents from the production of bitumens before and after chemical treatment, in which six compounds were identified, including 2-mercaptoethanol, thiophenol, thioanisole, dipropyl disulfide, 1-decanethiol, and phenyl isothiocyanate at concentrations ranging from 0.47 to 8.89 mu g/L. Problems in the determination of organosulfur compounds related to considerable changes in composition of the effluents, increase in concentration of individual compounds and appearance of secondary pollutants during effluent treatment processes are also discussed.