Potentiometric Determination of Alkyl Dimethyl Hydroxyethyl Ammonium Surfactant by a New Chemically Modified Carbon Past Electrode

This paper introduces the development a new chemically modified carbon paste electrode (CMCPE) for the determination of a cationic surfactant. The paste is based on alkyl dimethyl hydroxyethyl ammonium chloride (ADHACl) with phosphomolybdic acid as an ion-exchanger (ADHA-PM). The electrode exhibits a Nernstian slope of 59.1 +/- A 0.5 mV/decade for ADHA ions in the concentration range 1.0 x 10(-6)-1.0 x 10(-3) M with the limit of detection of 8.2 x 10(-7) M. The proposed electrode has a fast and stable response time of 5-8 s, a good reproducibility and it can be used in the pH range of 2.2-9.0. Selectivity coefficients, determined by a matched potential method and separate solution method, showed high selectivity for ADHA over a large number of inorganic cations and organic cations. These characteristics of the electrode enable it to be used successfully for determination of ADHA in shampoo and liquid detergents solutions by standard addition and the calibration curve methods. In addition, the modified electrode was applied as an indicator electrode in potentiometric titration and successfully used to determine ADHA in water samples with satisfactory results.