Potentiometric determination of cetylpyridinium chloride in oral desinfectants by flow injection analysis

The work describes a new procedure for cetylpyridinium chloride determination in oral disinfectants, based on a flow-injection system with potentiometric detection. The determination was based on the measurement of picrate concentration decrease as result of ion-pair reaction with the analyte present in the injected sample. In the optimised set-up the sample injection volume was kept at 400 muL and merged downstream with the reagent solution containing 10x10(-5) mol/L of picrate adjusted to pH 5.0 with citrate/citric acid buffer. The flow rate was fixed at 8 mL/min and the reactor length at 40 cm. The proposed procedure enables the determination of cetylpyridinium in the analytical range of 5,0x10(-6)-7,5x10(-5) mol/L at a sampling rate of 60/h. The results for real samples had a precision better than 3% and were comparable to the labelled values.