title: Direct spectrophotometric determination of quercetin in the presence of ascorbic acid.
abstract: The current research provides a simplified sample preparation procedure for the accurate estimation of quercetin in pure and in the pharmaceutical dosage form. Direct spectrophotometric method for the determination of quercetin in the presence of ascorbic acid was established. The influences of medium, wavelength, pH, temperature and the ionic strengths on quercetin determination were investigated. The best conditions for calibration curve are: 50% ethanol, lambda = 370 nm, pH = 4.2, T = 34 degrees C and I = 7.5 x 10(-5) M. Beer's law is obeyed in the concentration range 1.0-12.0 microg ml(-1) for quercetin. The corresponding detection limit is 0.76 microg ml(-1). The proposed method was verified by analyzing Quercetin + C capsules, Twinlab.
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, Vojvode Stepe 450, P.O. Box 146, 11000, Belgrade, Yugoslavia.
authors.forename: N
authors.initials: N
authors.lastname: Pejic
authors.forename: V
authors.initials: V
authors.lastname: Kuntic
authors.forename: Z
authors.initials: Z
authors.lastname: Vujic
authors.forename: S
authors.initials: S
authors.lastname: Micic
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D011794:Quercetin / Q000032:analysis* / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods; D013696:Temperature
chemical_list: D012997:Solvents; D011794:Quercetin; D001205:Ascorbic Acid