INDIRECT TENSAMMETRIC METHOD FOR THE DETERMINATION OF NONIONIC SURFACTANTS .1. GENERAL-PROPERTIES OF THE ANALYTICAL SIGNAL

An indirect method for the determination of non-ionic surfactants is based on the lowering of the tensammetric peak height of ethyl acetate by competitively adsorbed surfactants. The behavior of the tensammetric peak of ethyl acetate was examined (peak height vs. concentration of ethyl acetate and vs. initial potential). The dependence of the analytical signal on surfactant concentration for numerous oxyethylated alcohols, oxyethylated alkylphenols and oxyethylated amines having different numbers of oxyethylene subunits was examined, and also for several oxyethylene-oxypropylene block copolymers and poly(ethylene glycols), polypropylene glycol, oleyl alcohol and ethylene glycol. In all the instances this dependence exhibits a plateau or a pseudo-plateau. The position of the plateau increases roughly in proportion to the increase in the number of oxyethylene subunits in the molecule. Calibration graphs were constructed within the concentration range 100-1000-mu-g l-1 for ten oxyethylated alcohols and five oxyethylated alkylphenols. Triton X-100 was selected as the surfactant for calibration. The method enables all non-ionic surfactants separated from surface water by gas stripping, i.e., those having 1-30 oxyethylene subunits, to be determined.