A liquid chromatographic system for measurement of organic acids in precipitation.

An ion chromatographic system has been developed for routine measurement of carboxylic acids with carbon numbers up to C8 in precipitation samples. The system combines on-line sample preconcentration on a low-capacity anion exchange resin with separation by ion exclusion and subsequent detection by UV absorption. Detection limits of less than 0.4 mymol/L are obtained for formic acid and acetic acid. Mineral acids such as sulfuric, nitric and hydrochloric acids, which usually represent the main anions in continental precipitation over the northern hemisphere, do not interfere, since they elute as one peak in the beginning of the chromatogram. The chromatographic system has been tested for overlapping peaks with a variety of C1-C8 carboxylic acids, both saturated and unsaturated, substituted and unsubstituted, and with phenol and benzene.