title: Determination of sildenafil citrate and its main metabolite by sample stacking with polarity switching using micellar electrokinetic chromatography.
abstract: Micellar electrokinetic capillary chromatography (MEKC) coupled with sample stacking and polarity switching was investigated for the determination of Viagra (sildenafil citrate, SC) and its metabolite (UK-103,320, UK) in human serum in the concentration range of clinical interest. Human serum samples spiked with SC and UK were eluted with methanol from a C18 cartridge, the extract was evaporated and regenerated in a solution that contained 1 mM phosphate buffer (pH 12.3) and 20% methanol. The MEKC separation was performed using an injection time of 275 s, a polarity switching time of 93 s, a phosphate buffer, (pH 12.3, 15 mM) containing 25 mM sodium dodecyl sulfate as separation electrolyte and a fused-silica capillary. The analysis takes about 6 min and gives satisfactory inter-day precision with respect to migration times and linear responses over the 80-900 ng/ml concentration range investigated for SC and UK. Intra-day RSDs (n=4 graphs) for the slopes of the calibration graphs were 4.86% for SC and 3.50% for UK. Inter-day RSDs for the slopes were 4.37% for SC and 5.39% for UK. Detection limits (S/N=3) were about 17 ng/ml for both compounds in human serum. A 1-ml volume of blood serum was necessary to do this determination.
authors.affiliation: Departamento de Química Analítica y Tecnología de Alimentos, Facultad de Químicas, Universidad de Castilla-La Mancha, Ciudad Real, Spain.
authors.forename: J J
authors.initials: JJ
authors.lastname: Berzas Nevado
authors.forename: J Rodriguez
authors.initials: JR
authors.lastname: Flores
authors.forename: G Castañeda
authors.initials: GC
authors.lastname: Peñalvo
authors.forename: Fariñas N
authors.initials: FN
authors.lastname: Rodríguez
mesh_terms: D002138:Calibration; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D004573:Electrolytes; D006801:Humans; D009994:Osmolar Concentration; D010879:Piperazines / Q000097:blood*; D011687:Purines; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000068677:Sildenafil Citrate; D012967:Sodium Dodecyl Sulfate; D013450:Sulfones
chemical_list: D004573:Electrolytes; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D012967:Sodium Dodecyl Sulfate; D000068677:Sildenafil Citrate