Analysis of trihalomethane formation potential in river water using dispersive liquid-liquid microextraction technique

Abstract

Trihalomethanes (THMs) in treated water are formed when natural organic matter (NOM) reacts with chlorine, which is used as a disinfectant agent. Although the chlorination of drinking water provides many advantages, THMs remain a human health concern. High levels of the THMs in water leads to the possible carcinogenic effects which effect human health seriously. A new extraction technique named dispersive liquid-liquid microextraction (DLLME) was developed and applied for the determination of the formation of THMs in treated water. Different experimental conditions, for instance type and volume of disperser solvent, type and volume of extraction solvent, addition of salt and extraction time were investigated to obtain the optimum extraction conditions. In this method, the appropriate mixture of an extraction solvent (20.00 µL carbon disulfide) and disperser solvent (0.25 mL methanol) was injected in 5.00 mL aqueous sample containing the analytes to form a cloudy solution. The analytes were separated and enriched in a settled phase by centrifugation for 2 min at 4,000 rpm. Settled phase formed was determined by gas chromatography with electron-capture detection (GC-ECD). The repeatability and reproducibility of DLLME-GC-ECD were found to range between 1.1% to 11.4% and 3.4% to 10.9% respectively. Good correlation coefficient, R2 more than 0.9977 were obtained for all THMs compound. The LODs for all THMs compound ranged from 0.011 µg/L to 0.239 µg/L, whereas the enrichment factor (EF) obtained were found in the range of 95 to 283. DLLME-GC-ECD was found to be rapid and simple method which offered better sensitivity and high efficiency compared to conventional method, liquid-liquid extraction (LLE). The method was applied for analysis of total THM formation potential (TTHMFP) in river water. From the monitoring conducted during rainfall season at Batu Pahat, Johor Malaysia, it can be concluded that TTHMFP in Malaysian river waters especially at Johor area are still under the limits of 80 µg/L.