Modified carbon paste sensor for cetyltrimethylammonium ion based on its ion-associate with tetrachloropalladate(II).

A comparative study was made between developed chemically modified carbon paste electrodes and PVC membrane electrodes for the cationic surfactant cetyltrimethylammonium bromide (CTAB). The carbon paste electrode modified with cetyltrimethylammonium-tetrachloropalladate(II) (CTA-TClP) provides a more sensitive and stable device than that shown by electrodes with an inner reference solution. The best performance was obtained by an electrode based on the paste containing 3.6 wt% CTA-TCIP, 1.8 wt% ethylhexadecyldimethylammonium bromide, 37.6 wt% graphite and 57 wt% tricresyl phosphate. The sensor exhibited a Nernstian response for CTAB over a wide concentration range of 3.5 x 10(-7) to 1.0 x 10(-3) M with a detection limit of 2.0 x 10(-7) M between pH 2.7 and 8.2 with a fast response time of <or=15 s. The electrode showed excellent selectivity for CTAB over a large number of ions. Interferences caused by common cationic surfactants have been investigated in simulated mixtures containing high concentration levels of interfering surfactants, and the sensor was found to be tolerant against these compounds.