Application of Sequential Injection Analysis to the Determination of Cationic Surfactants Based on the Sensitized Molybdenum-Bromopyrogallol Red Reaction

Abstract

The aim of this work was to develop a simple, automatic system for the evaluation of cationic surfactants by combining sequential injection analysis and the sensitized effect of cationic surfactants on the reaction between metal ions and chelating dyes. This reaction is based on the increase in absorbance of the complex formed among molybdenum, bromopyrogallol red and increasing concentrations of cationic surfactants. Under optimum conditions, two calibration plots were obtained for a concentration range between 2.50 × 10 -7 mol dm -3 (detection limit) and 5.00 × 10 -4 mol dm -3 of cetylpyridinium chloride, used as standard. Solubilization of water insoluble complexes formed for concentrations of cationic surfactants greater than 1.00 × 10 -4 mol dm -3 were successfully achieved with Triton X-405. RSD values lower than 5.0% were obtained in all cases. The quality of the results obtained for 18 water samples were evaluated by comparison with conventional methods, with no statistically significant differences for a 95% confidence level.

Spectrophotometric Determination of Cationic Surfactants Based on Their Effect on the Complexes of Chrome Azurol S with Be2+ and Al3+ Cations

“…They also extended the surfactant to the dye binding degree (SDBD) method for the first time to the determination of CSs [16]. The effect of CS on the absorption spectra of the complex formed by the molybdenum(VI) and bromopyrogallol red was used to the spectrophotometric determination of CS [17]. Lavorante et al [18] proposed a spectrophotometric method for the determination of CS based on a ternary complex formation between Chrom Azurol S, the Fe(III) ion, and the CS.…”

A review on sequential injection methods for water analysis

“…Their presence results from human consumption and excretion and their environmental impact is yet not fully known but is an area of concern. Other emerging analytes in natural and drinking waters include surfactants (nonionic [30], anionic [65] and cationic [64]). These parameters are the consequence of sources of contamination that were not previously considered, in most cases excess of disinfectants and/or detergents used to clean up the water supplies.…”

“…In about 30% of the publications, the described methodology required a previous treatment. Most of those mentioned previous treatments were as simple as a filtration of the sample when waste water was involved [64,67,91,118,119,141,142,146]. In the work by Nyman and Ivaska [154], centrifugation of the sample was used with the same purpose.…”