Fabrication and voltammetric study of lanthanum 2,6-dichlorophenolindophenol chemically modified screen printed electrodes. Application for the determination of ascorbic acid

A screen printed carbon electrode (SPCE) impregnated with the electrocatalyst 2,6-dichlorophenolindophenol lanthanum salt ([DCPI](3)La) was constructed. Using cyclic voltammetry the electrochemical behaviour of SPCE, -SPEs and their catalytic effect towards ascorbic acid was investigated. A synthesis protocol ([DCPI](3)La) and some identification studies are given. The fabrication of (SPE) using a mixture of 5% (w/w) [DCPI](3)-La/graphite powder in 1 and 2% (w/v) ethyl cellulose in 2-butoxyethylacetate is also described. Constant potential amperometry in stirred solutions was used for the determination of ascorbic acid in beverages and pharmaceuticals potential of +0.1V versus Ag/AgCl, at pH 7.25 was employed. This technique was also used to assess the reproducibility of the electrode manufacture. Interference of various compounds was also studied. Good correlation with the official titrimetric method was attained. Calibration graphs were linear over the range 0.01-1 mM ascorbic acid and the RSD was 1.8% (n = 9) for 0.6 mM ascorbic acid. Recovery ranged from 91 to 103%. The [DCPI](3)-La-SPE showed very good storage and operational stability. (C) 2000 Elsevier Science B.V. All rights reserved.