A composite consisting of microporous carbon and cobalt(III) oxide and prepared from zeolitic imidazolate framework-67 for voltammetric determination of ascorbic acid

Abstract

A nanoporous carbon/cobalt oxide (NPC/Co3O4) composite was synthesized from a single-precursor (zeolitic imidazolate framework-67). Transmission electron microscopy showed that the Co3O4 nanoparticles with an average particle size of 10 nm (+/- 2 nm) were well dispersed in the NPC matrix. However, in a few places, Co3O4 nanoparticles were aggregated. The composite shows outstanding performance in terms of electrooxidation of ascorbic acid (AA) in phosphate buffer of pH 7.0. The differential pulse voltammetric response of the composite electrode (at 0.12 V vs. SCE) is linear in the 2-240 mu M AA concentration range, with a 20 nM detection limit. The electrode exhibits high sensitivity (0.13 mu A.mu M.cm(-2)), reliable reproducibility, and good selectivity. The method, when applied to the direct determination of AA in vitamin C tablets, gave recoveries between 98.0 and 102.0%.