INDIRECT DETERMINATION OF SURFACTANTS BY ADSORPTIVE VOLTAMMETRY .1. DETERMINATION OF TRACE AND ULTRATRACE CONCENTRATIONS OF SODIUM DODECYLBENZENE SULFONATE

The determination of sodium dodecylbenzene sulfonate based on the suppression of the adsorptive voltammetric response of nickel in the presence of dimethylglyoxime is described. Sensitive and accurate determination of the anionic surfactant is accomplished at trace and ultratrace concentrations by the use of a combination of electrodes, such as the hanging mercury drop electrode (HMDE), glassy carbon mercury film electrode (GCMFE), and a dropping mercury electrode (DME). The first two electrodes enabled the determination of sodium dodecylbenzene sulfonate down to ultratrace concentrations, while the latter was useful for rapid determination of trace concentrations of the surfactant. Despite the higher sensitivity obtained for the anionic surfactant on the GCMFE, the best limit of detection of 100 mu g/L and the optimum recovery efficiency of 104 +/- 8% were accomplished with the HMDE. Compared with the widely accepted spectrophotometric method, the adsorptive voltammetric approach is more rapid, has a much wider linear concentration range (based on the combined use of an HMDE or GCMFE and the DME), and is applicable at the ultratrace level.