Method development for the analysis of disinfection by-products coming from the chlorination of humic acid using pressurized capillary electrophoresis-electrospray mass spectrometry

Drinking tap water is processed worldwide. Close screening of the quality of what is being distributed to the public is important since hazardous compounds are produced during the water treatment process. Some of the compounds have been shown to be hazardous to humans.{09}It is highly suspected that some of these compounds like pentachlorophenol cause cancer. The most used disinfectant is chlorine, which is known to react with humic acid producing a great number of chemicals. Humic acid is present in water reservoirs, like lakes or rivers from which water is treated and delivered to the public.; Most of these chlorinated chemicals are acidic with different degrees of chlorination. The EPA has classified some of these compounds as disinfection by-products but the list is limited to volatile compounds only. The official method for disinfection by-products is based on gas chromatography (GC), which requires that the analyte be volatile and thermally stable. Many of these compounds have not been characterized completely because of the lack of a proper analytical technique to study them.; In this work a method is proposed based on pressurized capillary electrophoresiselectrospray ionization-mass spectrometry (CE-ESI-MS) to analyze chlorinated acidic compounds by capillary electrophoresis (CE) coupled with mass spectrometry (CE-MS). The sample injection is analyzed directly after a simple dilution is made. This method uses an in situ preconcentration technique, which takes place inside the separation capillary at the same time the injection occurs. Two model mixtures of 5 and 16 chlorinated and non chlorinated components were used to make validation tests on this method. The method was shown to be capable of detecting and analyzing tap water with concentration levels as low as 5 ppb. Higher molecular weight chlorinated compounds can be monitored based on the isotope's ratios of selected chlorinated ions. The degree of chlorination of an unknown peak can be determined. This method was compared with other CE methods as well as with EPA method 551.1 and was found to be much more reproducible (<2% RSD in migration time) and comparable in terms of linearity (correlation coefficient of 0.998), recovery (77 to 93%), accuracy (no statistical difference observed according to the student's t-test) and selectivity. This work suggests that this method can be used as a complementary method to the official EPA method for the analysis of acidic non-volatile or semi volatile compounds, which is limited to the volatile compounds.