Spectrophotometric determination of cationic surfactants in aqueous media using chrome azurol S as colour forming agent and 1-butanol as extracting solvent

摘要

A simple spectrophotometric method for the determination of cationic surfactants (CS) is developed using an anionic dye, chrome azurol S (CAS) as an ion-association complex forming agent, and 1-butanol as an extracting solvent. In the aqueous solution CS such as cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) and dodecyltrimethylammonium bromide (DTAB) reacts with CAS to form an ion-association complex which is extracted into 1-butanol to form a pink-violet coloured organic phase. The final concentration of CAS in surfactant solution is 165 mu M. The pH of the medium is maintained at similar to 6.4. The coloured compound exhibits maximum absorbance at 520 nm with a molar absorption coefficient in the range of (2.6-2.9) x 10(4)L mol(-1) cm(-1). Beer's law is obeyed in the concentration range of 0-82 mu M, 0-88 mu M and 0-84 mu M for CTAB, CPC and DTAB, respectively in normal condition. However, to minimize the interference of cations, the masking with EDTA has been proposed. In case of CTAB determination in EDTA masked double distilled water, the linear dynamic range (LDR) is found as 27-55 mu M. The proposed method is rapid, user-friendly and economical. The method is applied in mixed CS systems, and it showed good results. To check the reliability of the method, it has been applied for CS determination in real water samples masked with EDTA and spiked with CS of known concentration. The results obtained for recovery are quite satisfactory.