Amperometric Titration of Dodecyl Pyridinium Bromide with Sodium Dodecyl Sulphate

Abstract

RECENTLY, one of us (R. T., unpublished work) found that dodecyl pyridinium bromide gives a polarographic reduction wave in 0.1 M sodium hydroxide solution containing 0.2 mM polyoxyethylene lauryl ether as a maximum suppressor, the diffusion current measured at −1.325 V. vs. the saturated calomel electrode being proportional to the concentration of dodecyl pyridinium bromide in the range of 0.06—2.0 mM. The combination of this finding and the well-known fact that the reaction between cationic and anionic detergents often yields a very insoluble precipitate in aqueous solutions suggested to us the amperometric titration of dodecyl pyridinium bromide with one of the anionic detergents or vice versa. We consider the method proposed here to be much simpler and more accurate than those previously reported¹.