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A simple and sensitive HPLC method for the simultaneous analysis of free MPA and free MPAG was developed. Separation was achieved on a X-Terra RP18 column with acetonitrile–40 mM orthophosphoric acid as eluents using a gradient elution mode over 35 min at a flow rate of 1.5 ml/min. The assay was linear in the range 0.005 mg/L (LOQ) to 5 mg/L for free MPA and 0.05 mg/L (LOQ) to 200 mg/L for free MPAG. Isolation of free MPA and free MPAG was done by ultrafiltration and the ultrafiltrate was directly injected. A positive correlation between MPA free fractions and free MPAG concentrations was found. Likewise, free MPAG was related to total MPAG concentrations in the seven heart transplant patients.

A selective and sensitive high-performance liquid chromatographic method for the analysis of propofol in biological samples was developed. Propofol and thymol (internal standard) were analysed on a Purospher RP-18 endcapped (75 mmx4 mm, 3 microm) stationary phase using acetonitrile and water (65:35, v/v) as eluents at a flow rate of 0.6 mL/min. The excitation and emission wavelengths were 276 and 310 nm, respectively. Sample treatment consisted of deproteinization by acetonitrile containing the internal standard and direct injection of the supernatant. Mean analytical recovery were 105% (CV 2.0%) at concentrations ranging from 0.05 to 10 mg/L. The quantification limit was 3 ng/mL for a 500 microL sample plasma volume and 5 ng/mL for a 500 microL blood sample. The intra-day and inter-day precisions were lower than 5.5% for three concentrations assessed (0.05, 1.0 and 10.0 mg/L). Considering the column size and the flow rate, the separation was achieved with an analysis time less than 6 min with a reduced consumption of solvent. This rapid HPLC method using a simple treatment procedure is sensitive enough for monitoring propofol in human biological samples.

Drugs in solution may be adsorbed to the surface of containers and thus be removed from solution. We studied the loss of mycophenolic acid (MPA) and its major metabolite mycophenolic acid glucuronide (MPAG) from glass, polystyrene, and polypropylene containers based on solvent and time of contact. MPA was from Hoffmann-La Roche and MPAG from Analytical Services International Ltd. Acetonitrile (Uvasol; purity >99.8%), methanol (Uvasol; purity >99.8%), and orthophosphoric acid (85% Suprapur; Merck) were HPLC grade. The NaCl solution (9 g/L, pH 7.4) was from Fresenius Kabi. Stock solutions of MPA, MPAG, and MPA/MPAG were prepared in acetonitrile–water (80:20 by volume) and stored in polystyrene tubes at −80 °C. The chromatographic analysis was performed as described previously (1), with a minor gradient modification. Studies were performed on ice, which stabilizes drugs for at least 8 h (2). The MPA/MPAG stock solution was diluted with acetonitrile, methanol, or isotonic NaCl in five 6-mL glass (VSM; 69% SiO2, 13% Na2 …