Spectrophotometric determination of anions surfactants in water samples by congo red-cetylpyridinium bromide

In buffer solution of NaAc-HCl,when congo red(CGR) is mixed with the solution of cetylpyridinium bromide(CPB) after anion surfactant(AS) is added,the colour of the soluotion become deeper,and the max absorbtion wavelength is at 570 nm.At this wavelength,the absorbence enhancement is proportional to concentration of anion surfactant(AS).Based on it,a photometry method determining for anion surfactant was established.In the max absorbtion wavelength,anion surfactant(AS),namely,sodium lauryl sulfonate(SLS)and sodium dodecyl sulfate(SDS),in the 0～2.4×10-4 mol/L and 0～2.7×10-4 mol/L range obey Beer(s Law,and the apparent molar absorptivity(e) of 1.28×104 L/(mol.cm) and 1.19×104 L/(mol.cm),the detection limit of 1.43×10-6 mol/L and 1.08×10-6 mol/L are obtained respectively.The proposed method has good sensitivity and better anti-jamming ability and has been applied to the determination of anionic surfactant(AS) in water samples with satisfactory results.