Liquid chromatographic separation and simultaneous analyses of peroxycitric acid and citric acid coexisting with hydrogen peroxide in the equilibrium mixture

Abstract

The separation of peroxycitric acid (PCA) coexisting with citric acid (CA) and hydrogen peroxide in the equilibrium mixture and their rapid, direct (without derivatization), and simultaneous analyses were successfully carried out with a reversed-phase high-performance liquid chromatographic technique using 3 mM perchloric acid containing 33 mM sodium perchlorate additive as the mobile phase (pH 2.5) and a UV-vis detector. The conditions of separation of PCA from CA were optimized by measuring the chromatograms using different mobile phases containing various additives, with different pHs and temperature. We succeeded in utilizing the narrow (less than one unit) pKa difference between PCA and CA in the present separation process. The selectivity of column in the separation of PCA and CA was also examined. The maximum inter-day coefficient of variation was 8.7% and 9.1 % for CA and PCA, respectively. The calibration curves of CA and PCA were constructed and the limits of detection were determined to be 0.41 and 0.13 μM and the corresponding limits of quantification were 1.12 and 0.43 μM, respectively. The mechanism of separation of PCA from the coexisting CA and H2O2 was also discussed.