Derivatization-free multi-step extraction for trace haloacetic acids analysis with ion chromatography: Performance and mechanisms

Haloacetic acids (HAAs) are a type of disinfection byproducts commonly found in drinking water with carcinogenic, mutagenic, or teratogenic risks to humans. Currently, the analytical methods of trace HAAs are either labor-intensive or very expensive. We herein propose a facile multiple-step extraction strategy for HAAs analysis with common ion chromatography (IC). This study is based on a fundamental water chemistry principle that HAAs become protonated featuring positive log K ow values (> 0.34) under pH < pK a but deprotonated featuring negative log K ow values (< -2.37) under pH > pK a . By taking advantage of the species and property switches, HAAs can be extracted and enriched into methyl tert -butyl ether first at pH < 0.5 and then back-extracted into neutral water and enriched again. Equally important, interfering anions in IC chromatogram are eliminated because they have negative log K ow values. Verification results sh ow that HAAs were enriched by 11.4 times in average while interfering anions were almost eliminated (> 99%). Although similar to USEPA Method 552.3 in method detection limits (0.033~0.246 μg/L), recoveries (70%~110%), and relative standard deviations (< 9.91%), this method took ≤ 70 min to run a batch of samples without derivatization, which takes over 2 h. The methodology may be applicable to other pollutants that also have contrasting K ow values at different pH. • To save operation time and cost, we designed a facile and novel pretreatment method; • The method applies stepwise extraction and de-extraction processes before IC; • The method enriches HAAs based on their contrasting K ow features at different pH; • The method eliminates coexisting anions based on their pK a and/or K ow properties; • The method takes < 20 min for a batch of samples but achieves similar results as derivatization.