Effect of residual chlorine on the analysis of geosmin, 2-MIB and MTBE in drinking water using the SPME technique

The effect of chlorine on the analysis of three organic compounds (geosmin, 2-methylisoborneol (2-MIB) and methyl tert-butyl ether (MTBE)) in drinking water is elucidated. Three fibers for solid-phase microextraction (SPME) were employed for the extraction of the organic compounds from drinking water samples with and without free residual chlorine present. A gas chromatograph coupled with a mass spectrometer was used to analyze the compounds trapped by the fibers. The presence of chlorine substantially reduces the observed geosmin, 2-MIB, and MTBE concentrations. Depending on the analyte and chlorine concentrations, an experimental error of 10-70% may be observed due to the presence of free residual chlorine. The impact is larger for lower organic compound concentrations, and under higher residual chlorine conditions. To counteract the effect from residual chlorine, sodium thiosulfate was used to dechlorinate the water. After dechlorination the experimental error was less than 10%, suggesting that dechlorination is necessary when applying SPME for the extraction of organic compounds from chlorinated drinking water.