Graphite paste sensor modified with a Cu(II)-complex for the enzyme-free simultaneous voltammetric determination of glucose and uric acid in sweat

Abstract

In this work, a new type of graphite paste electrode (GPE) modified with a water-stable Cu(II)-complex is described as new candidate for the voltammetric determination of glucose (GLU) and uric acid (UA) in sweat. The oxidation of CLU and UA was electrocatalyzed by Cu(II) which was electrochemically generated in-situ from the Cu(II)-complex precursor. Three in-house synthesized water-insoluble Cu(II)-complexes {[Cu(PhCOO)(H2O)2]∙PhCOO·H2O}n, [Cu(Et-saoH)2] and [Cu(Me-saoH)2] (where, Et-saoH2: 2-hydroxypropiophenone oxime, Me-saoH2: 2-hydroxyethanone oxime) were synthesized and compared with conventional copper oxides (CuO and Cu2O) as electrode modifiers for the voltammetric detection of GLU and UA in acidic media. The {[Cu(PhCOO)(H2O)2]∙PhCOO·H2O}n exhibited the most favorable electrochemical performance and the determination of both biomarkers was carried out without interference from common electroactive metabolites presented in artificial sweat, offering low limits of detection (5 μmol L−1 GLU and 4.6 μmol L−1 UA). The results confirm that {[Cu(PhCOO)(H2O)2]∙PhCOO·H2O}n-modified GPE is a promising non-enzymatic sensor for the simultaneous determination of GLU and UA in sweat.