Determination of alkylphosphonic acids by microcolumn liquid chromatography with gradient elution coupled on-line with flame photometric detection

Microcolumn liquid chromatography with gradient elution and on-line flame photometric detection has been used for the selective and rapid determination of non-volatile alkylphosphonic acids, which are hydrolysis products of nerve agents, in aqueous samples. A make-up of water was used to maintain stable introduction of the eluent during a gradient run. The detection limits are strongly dependent on quenching, which is determined by the mass flow of methanol in the eluent. Large-volume injections of 100 microl of aqueous solutions of short- and long-chain alkylphosphonic acids resulted in detection limits in the range 6-800 ng/ml. The repeatability of the retention times and analyte response - peak area or peak height were 0.7-0.9% and 4-11%, respectively. The method was successfully applied to a local tap water sample and an aqueous soil extract.