Journal
JOURNAL OF PHARMACEUTICAL AND BIOMEDICAL ANALYSIS
Volume 33, Issue 5, Pages 1025-1031Publisher
ELSEVIER
DOI: 10.1016/S0731-7085(03)00412-6
Keywords
polyphenol oxidase; dopamine; biosensor; amperometry; pharmaceutical formulations
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The amperometric determination of dopamine (Do) in pharmaceuticals formulations by flow injection analysis (FIA) is proposed. An enzymatically modified carbon paste electrode constituted by 25% (w/w) of polyphenot oxidase obtained from Annona muricata L. tissue, 30% (w/w) of graphite, 30% (w/w) of silicone and 15% (w/w) of 7,7,8,8 tetracyanoquinodimethane (TCNQ), was used as flow-through detector. The flow amperometric detection was carried out at a potential of 0. 10 V (vs. Ag/AgG) when an injected sample volume of 250 mul was inserted on a 0.3 M phosphate buffer carrier solution (pH 7.8) flowing at 2.5 ml/min. The developed biosensor showed good stability and reproducibility, enabling up to 500 determinations in 60 days, without considerable loss of enzymatic activity. The FIA system presented a linear response to Do concentrations in the interval from 2 x 10(-2) to 2 x 10(-4) M, with relative standard deviations lower than 1.5%. The kinetic parameter Km for the soluble and immobilized enzyme was 1.45 x 10(-2) and 1.91 X 10(-2) M, respectively. In the analyses of different commercially pharmaceutical formulations a relative deviation lower than about 3.4% was obtained. (C) 2003 Elsevier B.V. All rights reserved.
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