Preconcentration and Rapid Spectrophotometric Determination of Polyoxyethylene Non-ionic Surfactants in Waters as Potassium Picrate Active Substances

The polyether chain of the polyoxyethylene non-ionic surfactants co-ordinates potassium cation in an aqueous solution and the positive complex is extracted into 1,2-dichloroethane as an ion-pair with picrate, which is the anionic chromophore for the spectrophotometric determination at 378 nm. Previous extraction of the non-ionics from the polluted waters by means of 1,2-dichloroethane eliminates the interference of the accompanying anionic surfactants and allows the determination of the Potassium Picrate Active Substances (PPAS). A rapid procedure for the extraction and determination of PPAS in waters at levels from 100 down to 5 μg/l is proposed. The validity of the method for the absolute determination of commercial polydisperse surfactants of the type R(OCH2CH2) n OH (n is the number-average degree of polymerization), derived from ethoxylation of primary alcohols from C10 to C18, is discussed.