Simple and specific method for flow injection analysis determination of cationic surfactants in environmental and commodity samples

A new, simple, rapid and specific flow injection analysis (FIA) procedure for the determination of cationic surfactants (CS) i.e. dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethyl-ammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) in the environmental and commodity samples is proposed. Their determinations are based on the enhancement of colour intensity of the Fe(III)-SCN- complex. The value of apparent molar absorptivity of the Fe(III)-SCN- -CS+ complexes in the terms of CS lie in the range of (2.10-4.30) x 10(3) l mol(-1) cm(-1) at absorption maximum 475 nm. The most sensitive surfactant, cetylpyridinium chloride (CPC) imparted detection limit (absorbance > 3 s) of 250 ppb CPC has been selected for the detailed studies. The working range is linear over 0.5-30.0 ppm CPC with slope, intercept, correlation coefficient and sample throughput of 0.67, 0.02, + 0.99 and 100 samples h(-1), respectively. The effect of analytical and FIA variables on the determination of the surfactant and the composition of the complex are discussed. The method is free from interferences of almost all ions which commonly associated with the surfactant in the environmental samples. The analytical potentiality i.e. sensitivity, linearity, precision and optimal analytical conditions of FIA to the manual system for the determination of the surfactant are compared. It is reproducibly applicable for the analysis of CS to the various environmental i.e. ground, surface, municipal waste water, and commodity i.e. detergent, soap, shampoo samples. (C) 1999 Elsevier Science B.V. All rights reserved.