Simultaneous Determination of Carboxylic Acids and Inorganic Anions by Photometric Ion Chromatography Application to Liquid Foods

Simultaneous determination of carboxylic acids and inorganic anions was investigated by photometric ion chromatography with phthalate solution as an eluent. The retention time and the peak area of carboxylic acids changed remarkably with eluent pH. The optimum conditions at present were as follows : analytical column, OYOBUNKO ASA-4000 (4.6 mm i.d.×25 cm) ; eluent, 5×10-4 M disodium phthalate ; flow rate, 2 ml/min ; column temperature, 40°C ; detection wavelength, 240 nm ; injection volume, 100 μl. The detection limits for several carboxylic acids as 3 times noise were 0.05-0.07 mg/l in sample solution. Their calibration curves showed straight lines by the peak area method. The present method has an advantage to determine simultaneously not only carboxylic acids but also inorganic anions. Under the condition described above, both carboxylic acids and inorganic anions in several liquid foods were easily determined by direct injection of the sample prepared with only dilution.