Sensitive and Selective Spectrophotometric and a new Adsorptive Stripping Voltammetric Determination of Sodium Dodecyl Sulfate in Nonaqueous Solution after its Extraction Using Toluidine Blue

Simple, sensitive and selective spectrophotometric and adsorptive stripping voltammetric (AdSV) methods for the determination of sodium dodecyl sulfate (SDS) after its separation using liquid-liquid extraction (LLE) are described. Trace amounts of SDS were extracted into dichloromethane, based on ion-paired complex formation between SDS and Toluidin blue in pH=2.5, in a single step extraction. The effect of different experimental parameters such as type and concentration of the cationic dye, type of the extracting organic solvent, pH of the sample solution, type and concentration of the additive agent and interfering effect of different ions were investigated. Under the optimal experimental conditions, absorbance of the organic extractant obeyed Beer's law over the range of 0.05-4.00 mu g mL(-1) of SDS and the LOD was 33.0 ng mL(-1). To asses the better analytical performance in determination of SDS, an AdSV method was also developed. Type of the electrode, accumulation potential and time, type and concentration of the supporting electrolyte and sweep rate, were optimized in the AdSV procedure. Linear dependence, between the current and concentration of the extracted SDS in organic phase, was observed over the range of 0.05-17.50 mu g mL(-1) for accumulation potential of 525 mV with time duration of 180s and 20 mV s(-1) as sweep rate. The LOD for AdSV method was 1.2 ng mL(-1). RSDs of 3.8% and 2.1% were obtained for 10 replicate analyses of 2.00 mu g mL(-1) SDS using spectrophotometric and AdSV determination methods, respectively. The proposed methods were applied successfully for the determination of SDS in wastewater samples.