Linear relationship between potential and concentration in flow potentiometry

In potentiometric-flow systems, linear-potential responses for logarithmic concentrations can be attained for first-(or pseudo-first-) order reactions in which the monitored chemical species react with the analyte during a fi xed time interval. To demonstrate this property, the determination of glyce rol based on its oxidation by periodate and potentiometric monitoring of th e remaining periodate was selected. Influence of reagent concentration and timing on the linearity of the analytical curve were investigated. A mathem atical treatment was derived, and potentialities/limitations of the approac h were outlined. The system was applied to analysis of soap and lixivia sam ples. The analytical curve within 200 and 2000 mg L-1 (r = 0.99975; n = 5) was described as E = 8.166 + 0.0478 (glycerol). The sample throughput was 1 00 h(-1), and a measurement repeatability within 0.5 mV was always observed . By applying a t-test, there was no statistical difference between the res ults obtained by the proposed procedure and by iodimetric titration at the 95% confidence level. (C) 2000 John Wiley & Sons, Inc. Lab Robotics and Aut omation 12:41-45, 2000.