Application of post-column reaction to speciate disinfectants and disinfection by-products.

摘要

Two methods, independent of each other, are developed and optimized separately. Both methods use the same approach, the use of chromatography technique followed by post-column reaction for the analysis of haloacetic acids and chloramine compounds.;The first method, post-column reaction ion chromatography analyzer with internal standardization (IS-PCR-IC), is optimized to determine nine haloacetic acids (HAAs) in drinking water, operating in near real-time. The IS-PCR-IC method requires a minimal sample preparation that consists of passing water samples through cartridges to remove chloride and sulfate ions and introducing the pretreated samples into the on-line channel of the automated instrumentation. Two sets of water samples are analyzed and method detection limit (MDL), accuracy, and precision studies are conducted prior to the water sample analyses. The experimental MDL values for the HAAs range from 1.4 to 7.8 microg/L; the mean percent recovery values range from 75.9 to 111.5%; and the percent relative standard deviation values range from 6.2 to 34.6%. The concentration of each HAA and the total concentration of five regulated HAAs and nine HAAs found in these water samples are determined in one hour run using internal standardization method; and the results are compared to the USEPA Method 552.3. The bias values between these two methods for total concentration of all nine HAAs range from 0.4 to 12.5 microg/L. In addition, a reaction mechanism of HAAs with nicotinamide (post-column reagent) is proposed. The formation of intermediates and products are explained from spectrophotometric studies and also from a mass spectrometry product investigation study. The spectrophotometric studies are carried out in order to understand the post-column reaction chemistry as well as the reaction rates of HAAs with nicotinamide.;The second method, post-column reaction high performance liquid chromatography (PCR-LC), is developed to analyze and speciate inorganic and organic chloramines. The PCR-LC method is developed to be used in isocratic elution and gradient elution. Seven inorganic and organic chloramines are separated in less than ten minutes. Stability studies are carried out prior to method detection limit (MDL), accuracy, and precision studies. The experimental MDL values for the chloramine species range from 2 to 690 microg/L; the mean percent recovery values range from 85.8 to 130.1%; and the percent relative standard deviation values range from 1.9 to 12.7%.