Fabrication of directly polymerized 4-vinylpyridine onto a pencil 2B graphite paste electrode for glucose monitoring

4-vinylpyridine was polymerized anodically at its optimum onto a pencil 2B graphite paste electrode when its concentration was 0.003 M, current density 21 μA cm−2, pH 3.0, scan rate 50 mV s−1, equilibration time 100 s and at a constant potential of +0.40 V vs. SCE. Initial investigation indicated that the polymerization was affected by the type of supporting electrolyte and solvent used. The surface morphology of the film grown was compared with films on other types of electrodes, viz. pencil rod and pyrolytic graphite paste. A charge density of 250 mC cm−2, i.e. equivalent to a polymer film 0.7 μm thick was taken as the optimum value to maximize current response for glucose detection. The dip coating enzyme immobilization technique was utilized as it has produced the best current response among other techniques used, i.e. in-situ incorporation (during the polymerization at pH 6.4) and dropwise addition. The linear response range was 1–14 mM glucose, with a slope of 32.5 μA mM−1 and the lower detection limit was 0.5 mM. The response time observed was 25 s. The apparent Michaelis–Menten constant, Km, was 9 mM which substantiated the viability of the electrode. The effect of common interferents in glucose determination are also reported. The operational life of the electrode spanned over a week of constant use under normal laboratory condition.