Simultaneous determination of mixtures of organic acids or bases based on the differences in the titration spectra

Based on the differences in titration spectra, mixtures of organic acids with similar p K-a were determined simultaneously. Principal component regression calibration was used for the evaluation of titration spectra. The effects of differences in pK(a) and sampling interval of pH on accuracy were studied in detail. Combining precipitation and the acid-base reaction of organic acid, precipitation-acid-base titrimetry is proposed, The mixture of acids with almost the same pK(a) can be determined simultaneously and accurately only if their pK(sp) values are different. Synthetic mixtures of isomer of chlorobenzoic acid and homologue of phenol were determined simultaneously and acceptable results were obtained. (C) 1999 Elsevier Science B.V. All rights reserved.