Extraction and determination of anionic surfactants with copper (II)-ethylenediamine derivative complexes

Anionic surfactants, S(-) [where S(-) is dodecyl sulphate (DS) or dodecylbenzenesulphonate (DBS)] were extracted with a series of copper (II)-ethylenediamine derivative complexes, CU(R-en)(2)(2+), where R-en is ethylenediamine (en), N,N'-dimethylethylenediainine (NN'Me(2)en), N,N-dimethylethylenediamine (NNMe(2)en), N,N-diethylethylenediamine (NNE(2)en) or 1,2-cyclohexanediamine (Cyen). The extraction constant of the ion-pair is K(ex) = [Cu(R-en)(2)(2+) . 2S(-)](0)/[Cu(R-en)(2)(2+)][S(-)](2). The constants for extraction of the DS complexes with en, NN'Me(2)en, NNMe(2)en, NNEt(2)en and Cyen into chloroform were found to be log K(ex) = 7.93, 9,19, 8.88, 8.74 and 11.45 (+/- 0.05 at 25 degrees C), respectively. The extractability of the ion-pair Cu(en)(2)(2+) . 2S(-) gave a linear correlation with the acidity of the solvent. The Cu(Cyen)(2)(2+) extraction system was applied to the determination of some anionic surfactants. With use of graphitefurnace atomic-absorption spectrophotometry, a limit of detection of 5mug l . was obtained with a 20-ml sample of river water or sea-water.