Flow injection determination of anionic polyelectrolytes using an anionic surfactant-selective plasticized poly(vinyl chloride) membrane electrode detector

A potentiometric flow injection method for the determination of anionic polyelectrolytes utilizing a flow-through type surfactant-selective electrode detector is described. The method is based on the detection of the concentration increase of anionic surfactant liberated from a reagent stream containing an ion associate between cationic polyelectrolyte, poly(diallyldimethylammonium chloride) and anionic surfactant, dodecylbenzenesulfonate, which is caused by the formation of a polyion complex between cationic and anionic polyelectrolytes. The response of the electrode detector as a peak-shaped signal was obtained for injected anionic polyelectrolyte samples. A linear relationship was found to exist between peak height and the logarithmic concentration of potassium poly (vinyl sulfate) (PVSK) with a slope of 30 mV decade^-1 in a concentration range of 1.0 × 10^-4 to 1.0 × 10^-3 mol/L. Identical relationships were obtained for sodium alginate and carageenan (also anionic polyelectrolytes) as for PVSK but with a lower sensitivity. The detection limit for PVSK was 2.5 × 10^-5 mol/L. The relative standard deviation for 5 injections of a 2.5 × 10^-4 mol/L PVSK solution was 1.3% and the sampling rate was ca. 10 samples h^-1.