title: Flow-injection spectrophotometric determination of methyldopa in pharmaceutical formulations.
abstract: A flow-injection spectrophotometric procedure is proposed for methyldopa determination in pharmaceutical preparations. The determination is based on formation of a yellow product (measured at 410nm) after complexation of methyldopa with molybdate. Under optimal conditions, Beer's law is obeyed in a concentration range of 50-200mgl(-1) methyldopa. Typical correlation between absorbance and analyte concentration was 0.9999. Usual excipients used as additives in pharmaceuticals do not interfere with the proposed method. The analytical frequency was 210h(-1) and the relative standard deviation (R.S.D.) was </=2% for sample solution containing 150mgl(-1) methyldopa (n=11). The analytical results obtained in commercial formulations by applying the proposed FIA method were in good agreement with labeled values and those obtained by the Brazilian Pharmacopoeia procedure at 95% confidence level.
authors.affiliation: Instituto de Química-UNESP, P.O. Box 355, CEP 14801-970, Araraquara, SP, Brazil.
authors.forename: P R S
authors.initials: PR
authors.lastname: Ribeiro
authors.forename: J A Gomes
authors.initials: JA
authors.lastname: Neto
authors.forename: L
authors.initials: L
authors.lastname: Pezza
authors.forename: H R
authors.initials: HR
authors.lastname: Pezza