title: An ionic liquid coating for determination of sildenafil and UK-103,320 in human serum by capillary zone electrophoresis-ion trap mass spectrometry.
abstract: Ionic liquid (IL) was covalently bonded onto the silica capillary surface and the electroosmotic flow was reversed over a pH range of 3.5 to 7. Sildenafil (SL) and its metabolite UK-103,320 (UK) in human serum were detected by solid-phase extraction followed by capillary zone electrophoresis-mass spectrometry analysis. The running buffer contained 10 mM acetic acid adjusted to pH 4.5 with 1 M ammonia, and the separating voltage was set to -25 kV. The adsorption of the analytes onto the bare capillary wall was eliminated by the IL coating and the drugs were baseline-separated within 14 min with detection limits (S/N = 3) of 14 and 17 ng/mL for SL and UK, respectively. The method developed showed good intraday precision in terms of relative standard deviation (RSD) with respect to migration time (RSD </= 0.76%, n = 5) and peak area (RSD </= 3.4%, n = 5); the relative coefficients of linear regression for both targets were better than 0.99 within linear dynamic range (SL: 50-600 ng/mL; UK: 40-400 ng/mL). Satisfactory interday precision was obtained with respect to the slope of the regression (RSD </= 4.21%, n = 9) and the migration time (RSD </= 1.1%, n = 9). The IL coating could be used with stable electroosmotic flow (RSD = 2.78%, n = 10) for at least 80 h.
authors.affiliation: Department of Chemistry, National University of Singapore, Republic of Singapore.
authors.forename: Weidong
authors.initials: W
authors.lastname: Qin
authors.forename: Sam F Y
authors.initials: SF
authors.lastname: Li
mesh_terms: D000478:Alkylation; D002021:Buffers; D019075:Electrophoresis, Capillary / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D015394:Molecular Structure; D010726:Phosphodiesterase Inhibitors / Q000097:blood; D010879:Piperazines / Q000097:blood* / Q000737:chemistry; D011687:Purines; D011744:Pyrimidinones / Q000097:blood* / Q000737:chemistry; D000068677:Sildenafil Citrate; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013450:Sulfones
chemical_list: D002021:Buffers; D007202:Indicators and Reagents; D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D011744:Pyrimidinones; D013450:Sulfones; C109995:UK 103320; D000068677:Sildenafil Citrate