Atomic absorption spectrophotometric determination of polyoxyethylene-type nonionic surfactants in water.

A simple, precise and sensitive method for the determination of polyoxyethylene-type nonionic surfactants in water was established by using atomic absorption spectrophotometry with a graphite furnace atomizer. The proposed method is based on the atomic absorption spectrophotometric determination of cobalt in a chelate complex produced by the reaction of nonionic surfactants with ammonium cobaltothiocyanate reagent used in the spectrophotometric method of JIS K 3364 and K 0102. The interference by anionic and cationic surfactants could be removed by a cleanup procedure involving ion exchange resin column chromatography. The recoveries of polyoxyethylene-n-dodecyl ether as a standard compound in various environmental water samples were within the range of 93.0-111.3% and the coefficients of variation were within 9.0% ; these values are satisfactory. The proposed method does not require any preliminary concentration procedure because of the high sensitivity (detection limit : 0.001 mg/l). There was a highly significant correlation (γ=0.999) between the results obtained by the proposed method and those of the JIS K 3364 and K 0102 spectrophotometric method. The assayed values of nonionic surfactants in water samples obtained from 18 rivers were distributed between 0.001 and 0.895 mg/l.