NICKEL-OXIDE DISPERSED IN A GRAPHITE/POLY(VINYL CHLORIDE) COMPOSITE MATRIX FOR AN ELECTROCATALYTIC AMPEROMETRIC SENSOR OF ALDITOLS IN FLOW-INJECTION ANALYSIS

A novel chemically modified electrode prepared from nickel oxide dispersed in a graphite powder and poly(vinyl chloride) (PVC) composite matrix (NiO-CME) was used for the electrocatalytic oxidation of alditols such as xylitol, sorbitol and mannitol, etc. in alkaline solutions. This bulk-phase modified electrode is well prepared in less than 15 min and its electrode surface is very robust, stable and easily polishable. The detector response was evaluated with regard to now rate, applied potential and catalyst loading. Amperometric detection in the flow-injection mode at the NiO-CME, using a wall-jet flow cell, showed a linear response up to 50 mM and detection limits of 20 mu M, 50 mu M and 80 mu M for xylitol, dulcitol, and mannitol, respectively. The performance of the sensor was assessed with respect to stability and sensitivity. A signal loss of less than 5% was observed during an operating period of 72 h.