Various analytical conditions of capillary electrophoresis (CE) have been examined for separation and detection of organophosphorous nerve gas hydrolysis products, methylphosphonic acid (MPA), ethyl-, isopropyl- and pinacolyl methylphosphonic acid (EMPA, IMPA and PMPA). Seven analytical conditions were tested and compared with regard to detectability, quantitability, and the influence of high levels of chloride and carbonate. The detection limits for MPA and its monoalkyl esters varied from 0.01 ppm to 50 ppm. Peak detection was interfered by high levels of chloride and carbonate applied using three methods and depended on the types of ultraviolet-absorbing background ions contained in electrolytes, ways of detection and acidity of electrolytes (pH). Three conditions have been selected from the standpoint of sensitivity and influence of chloride and carbonate, and applied to the analysis of aqueous soil extract.