title: Carbon paste electrode modified with copper (II) phosphate immobilized in a polyester resin for voltammetric determination of L-ascorbic acid in pharmaceutical formulations.
abstract: A carbon paste electrode modified with copper(II) phosphate immobilized in a polyester resin (CuP-Poly) is proposed for voltammetric determination of L-ascorbic acid in pharmaceutical formulations. The modified electrode allows the detection of L-ascorbic acid at lower anodic potentials than observed at unmodified electrodes. Several parameters that can influence the voltammetric response of the proposed electrode such as carbon paste composition, pH, scan rate, and possible interference were investigated. The peak current was proportional to the concentration of ascorbic acid in the range 2.0 x 10(-5) to 3.2 x 10(-3) mol L(-1) with a detection limit of 1.0 x 10(-5) mol L(-1). The stability and repeatability of the electrode for the determination of L-ascorbic acid are also discussed. Amperometric response was also recorded for electrocatalytic oxidation of the L-ascorbic acid. Concentrations of the vitamin C in pharmaceutical formulations (tablets) measured using the modified electrode and a titrimetric method are in agreement at the 95% confidence level and within an acceptable range of error.
authors.affiliation: Departamento de Química, Centro de Ciências Exatas e de Tecnologia, Universidade Federal de São Carlos, Caixa Postal 676, CEP 13.560-970, São Carlos, SP, Brazil. funcao@dq.ufscar.br
authors.forename: Marcos F S
authors.initials: MF
authors.lastname: Teixeira
authors.forename: Luiz A
authors.initials: LA
authors.lastname: Ramos
authors.forename: Orlando
authors.initials: O
authors.lastname: Fatibello-Filho
authors.forename: Eder T G
authors.initials: ET
authors.lastname: Cavalheiro
mesh_terms: D001205:Ascorbic Acid / Q000032:analysis*; D002244:Carbon / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D011091:Polyesters / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D004364:Pharmaceutical Preparations; D010710:Phosphates; D011091:Polyesters; D002244:Carbon; D003300:Copper; D001205:Ascorbic Acid