Novel PVC-free All-solid-state Ion-selective Electrode for Determination of Chlorhexidine in Pharmaceutical Formulations

The potentiometric response characteristics and analytical applications of a poly(vinyl chloride) (PVC)-free all-solid-state ion-selective electrode for chlorhexidine (CHX) are examined and compared to those of PVC-based solid-state electrode. The PVC-free electrode is prepared by direct incorporation of chlorhexidine-tetraphenyl borate (CHX-TPB) as a sensing element into a commercial nail varnish (NV) containing cellulose acetate propionate. The composite was applied onto a 3 mm diameter graphite disk-electrode. The electrode exhibited a Nernestian slope of 29 mV/decade in the concentration range from 10-5 to ≤10-3 mol/L with a detection limit of 4×10-6 mol/L. The electrode is independent of pH in the range from 3.6 to 7.9. Cationic inorganic ions showed negligible interference, whereas, a strong electrode response was observed for cetrimide and benzalkonium chloride with selectivity coefficients of 8.62 and 7.59 respectively. Comparable pH working range and selectivity pattern were observed with the PVC-based electrode. The electrode was used for determination of CHX in mouthwash and gargle, without extraction, with high precision (%RSD≤2) and accuracy (±2%). The new electrode is simple, economical and rapid when compared to the PVC-based electrode.