Highly selective determination of macromolecular chlorolignosulfonic acids in river and drinking water using Curie-point pyrolysis gas chromatography tandem mass spectrometry

A highly selective pyrolysis-gas chromatography-tandem mass spectrometry (Py-GC-MS-MS) procedure for the quantitative determination of high molecular weight (MW > 1000) chlorolignosulfonic acids in river and drinking water is presented. The use of MS-MS considerably enhanced the selectivity toward 2-methoxy-5-chlorophenol (5-chloroguaiacol; a highly characteristic pyrolysis product of chlorolignosulfonic acids) as compared to SIM conditions. The dissociation of the parent ion at m/z 143 (C6H4ClO2+) into the daughter ion at m/z 115 (C5H4ClO+, loss of CO) was monitored due to its high selectivity in the complex pyrolysates. Standard addition quantification appeared to be mandatory due to a strong matrix dependency of the pyrolysis efficiency of 5-chloroguaiacol from the chlorolignosulfonic acids. A repeatability of 5% RSD (n = 5) was obtained for a prepurified drinking water sample. The detection limit of the procedure is 0.5 mu g/L (S/N = 3) of chlorolignosulfonic acids in drinking water and has been decreased by a factor of 60 as compared to the former Py-GC-MS-SIM procedure. The CLSA concentrations in the river Rhine have decreased strongly during the past 5 years, leading to CLSA concentrations of ca. 26 mu g/L at present. It was found that the waterworks WRK [which produces prepurified drinking water using coagulation with Fe(III)Cl-3 and rapid sand filtration] showed an average water purification efficiency of CLSA of 51%; S-x = 27%. The waterworks GWA (which produces finished drinking water using among others ozonization combined with biological active carbon filtration) showed a purification efficiency of 92-93% for CLSA, which resulted in low (0.6-0.8 ug/L) concentrations of CLSA in drinking water of the city of Amsterdam. The analytical strategy for the selective and quantitative determination of CLSA can possibly be applied to other synthetic polymer classes in water.