HPLC‐DAD method for the simultaneous determination of zofenopril and hydrochlorothiazide in oral pharmaceutical formulations

An HPLC method with DAD detection was developed and validated for the simultaneous determination of zofenopril and hydrochlorothiazide in tablets. The separation was carried out through a gradient elution using an Agilent LiChrospher C18 column (250×4.0 mm id, 5 μm) and a mobile phase consisting of (A) water–TFA (99.9:0.1 v/v) and (B) acetonitrile–TFA (99.1:0.1 v/v) delivered at a flow‐rate of 1.0 mL/min. 8‐Chlorotheophylline was used as internal standard. Calibration curves were found to be linear for the two drugs over the concentration ranges of 5.0–40 and 1.0–20 μg/mL for zofenopril and hydrochlorothiazide, respectively. Linearity, precision, accuracy, specificity and robustness were determined in order to validate the proposed method, which was further applied to the analysis of commercial tablets. The proposed method is simple and rapid, and gives accurate and precise results.     

Coordination symmetry-dependent structure restoration function of one-dimensional MOFs by molecular respiration

One-dimensional metal-organic compounds with cis, trans symmetry-controlled counter anions were synthesized (cis compound {[Cu(azpy)(H2O)2(OTs)2]*2H2O*(acetone)} (1) and trans compound {[Cu(H2O)4Cu(azpy)2(OTs)2(H2O)2]*2(OTs)*2H2O*2EtOH} (2)). Only 2, having trans conformation, exhibited a complete structure-restoration effect with a mechanism involving layering of molecular "bricks" of water and solvent molecules.     

Development of a CE method for the determination of mycophenolic acid in human plasma: a comparison with HPLC

Mycophenolate mofetil (MMF) is a widely used drug for the maintenance of immunosuppressive therapy in renal-transplant recipients. MMF is rapidly metabolized in vivo to mycophenolic acid (MPA), a reversible, noncompetitive inhibitor of inosine monophosphate dehydrogenase, which represents a limiting enzyme in lymphocyte proliferation. MPA shows large interindividual pharmacokinetic variability: its monitoring is therefore of primary importance to achieve adequate immunosuppression with minimized risk of graft rejection or toxicity. We developed a CE method for the determination of total MPA (tMPA) in plasma, based on easy sample preparation; CE evaluation of tMPA was performed in 30 mmol/L sodium-borate with 10 mmol/L SDS (pH 10.00) at 25 degrees C using a 60 cm (54.5 to window) uncoated capillary with UV detection at 254 nm wavelength. MPA was readily detectable in plasma; the CE method was linear in the range of 0.7-120 microg/mL (r >0.992). Intra- and interassay imprecision was <7% except for the lowest spiked MPA concentration, which had an intra-assay RSD% of 14.7 compared to 18.3 interassay. Data by CE were compared with results obtained by a validated HPLC method. CE assay of tMPA exhibited a very good correlation (r(2) >0.988) with respect to HPLC; Bland-Altman difference versus average showed a mean of -0.18 microg/mL +/- 1.14 SD. CE determination of tMPA is a robust, sensitive and reproducible method with the advantage over HPLC of being fast, simple and unexpensive, also enabling quick assessment of MPA for pharmacokinetic studies.     

A validated HPLC method with electrochemical detection for simultaneous assay of 5-aminosalicylic acid and its metabolite in human plasma

A high-performance liquid chromatographic method was developed, validated and applied to the simultaneous determination of 5-aminosalicylic acid (5-ASA) and its acetylated metabolite (acetyl-5-ASA) in human plasma. The method involves liquid-liquid extraction with methanol followed by isocratic reversed-phase chromatography on a Kromasil KR100 C(18) column with electrochemical detection. The recovery, selectivity, linearity, precision and accuracy of the method were evaluated from spiked human plasma samples. The effects of mobile phase composition, buffer concentration, mobile phase pH and concentration of organic modifiers on retention of 5-ASA, acetyl 5-ASA and internal standard were investigated. Limits' of detection were 5 ng/mL for 5-ASA and 10 ng/mL for acetyl-5-ASA, respectively. The method can be used for supporting therapeutical drug monitoring and pharmacokinetic studies.