Spectrophotometric determination of ionic surfactants on the basis of a color change of fluorescein dyes with a quaternary ammonium ion

• Published in: BUNSEKI KAGAKU Vol. 48; no. 1; pp. 87 - 93
• Main Authors: YAMAMOTO, Koichi, KADONO, Mutsuko
• Format: Journal Article
• Language: Japanese
• Published: The Japan Society for Analytical Chemistry 01.01.1999
• Subjects: determination of ionic surfactants; ion association of quaternary ammonium ion with anionic surfac tants; Phloxine B; Rose Bengal; spectrophotometry
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.48.87

A method for the spectrophotometric determination of ionic surfactants (cationic surfactants (CS+), such as quaternary ammonium salts containing a long-chain alkyl group, and anionic surfactants, such as sodium lauryl sulfate (LS-)) with Fluorescein dyes (Rose Bengal(RB), Phloxine B(PhB)), has been developed. The addition of CS+to RB or a PhB solution buffered at pH 3 leads to an increase in the absorbance at 568 nm or 558 nm, respectively; also, when LS- is added to the solution, the absorbance at 568 nm or 558 nm decreases with increasing amounts of LS-. This decrease in absorbance is caused by an ion association of CS+ with LS-. The calibration graph based on this principle shows linearity up to 1 × 10-5M of CS+and from 2 × 10-6 to 1 × 10 -5 M of LS- with RB and up to 1 × 10-5of CS+ and LS- with PhB. The proposed method is simple and rapid, and there is no use of toxic organic solvents. It was applied to the determination of anionic surfactants in commercial detergents, the results of which were in good agreement with those of the JIS titration method (Epton method).