Submicromolar determination of praepagen HY surfactant using new liquid inner contact electrodes

New liquid membrane electrodes for submicromolar determination of praepagen HYCl surfactant have been prepared. These electrodes utilize HYCl with phosphotungstic acid (PTA) as ion-pair (HY-PT) dissolved in the plasticizers: dibutyl phthalate (DBP) encoded sensor S1, dioctyl phthalate (DOP) encoded sensor S2, dioctylsebacate (DOS) encoded sensor S3 and tris(2-ethylhexyl) phosphate (TOPh) encoded sensor S4. The proposed electrodes exhibit Nernstian slopes of 59.5 ± 0.6, 58.5 ± 0.6, 55.2 ± 0.6 and 57.3 ± 0.5 mV/decade in the concentration ranges 1.0 × 10− 7-1.0 × 10− 2, 2.5 × 10− 8-1.0 × 10− 2, 8.0 × 10− 8-1.0 × 10− 2 and 1.0 × 10− 7-1.0 × 10− 2 M and notably low limits of detection: 1.0 × 10− 7, 2.0 × 10− 8, 3.5 × 10− 8 and 8.5 × 10− 8 M for sensors S1, S2, S3 and S4 respectively. The sensors have considerably short response times (5-10 s) and good repeatability within the pH range 2.8-9.4. The electrodes exhibit excellent selectivity for HY+ ions over many inorganic and organic cations. These electrodes are useful for determination of HYCl in shampoo and liquid detergent solutions as proved by standard addition and the calibration curve methods. Furthermore, the successful use as indicator electrode was culminated by the potentiometric titration of HY+ ions in water samples.