Flow-injection amperometric determination of dopamine in pharmaceuticals using a polyphenol oxidase biosensor obtained from soursop pulp.
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 polyphenol 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/AgCl) when an injected sample volume of 250 microl 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 K(M) 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.
Bezerra
Vilma Sobral
VS
Laboratory of Immunopathology Keizo Asami (LIKA), Department of Biochemistry, UFPE, 50670-901 Recife PE, Brazil.
de Lima Filho
José Luiz
JL
Montenegro
Maria Conceição B S M
MC
Araújo
Alberto N
AN
da Silva
Valdinete Lins
VL
D031041:Annona; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods* / Q000592:standards*; D004156:Catechol Oxidase / Q000032:analysis*; D004298:Dopamine / Q000032:analysis*; D004563:Electrochemistry; D017022:Flow Injection Analysis / Q000379:methods; D004364:Pharmaceutical Preparations / Q000032:analysis
D004364:Pharmaceutical Preparations; D004156:Catechol Oxidase; D004298:Dopamine