FLOW-INJECTION COULOMETRIC TITRATIONS

A flow-injection analysis technique based on stop flow coulometric titrations is described, utilizing a gradient chamber, reagent generation chamber, and detector flow cell integrated into a single unit. The use of stop flow allowed for automated sample dilution up to a factor of 100 times. The system has been used to titrate samples of sodium hydroxide in the range 5 x 10(-4)-4M, and nitric acid ranging from 5 x 10(-3)-15M. Analyses over the entire range of concentrations yielded a relative standard deviation of less than 3%. A correlation coefficient of 0.999 was obtained for all comparisons with manual titrations. Remote spectrophotometric detection was performed with optical fibers. No frit or membrane is required to separate the generating and counter electrodes within the system, yet the advantages of conventional coulometric titration, which eliminate the problems of reagent and calibration solution handling, storage or degradation, are retained.