Obtaining positions and widths of scattering resonances from a complex multiconfigurational self‐consistent field state using the M1 method

We present a complex multiconfigurational self‐consistent field (CMCSCF)‐based approach to investigate electron‐atom scattering resonances. It is made possible by the use of second quantization algebra adapted for biorthogonal spin orbitals, which has been applied to develop a quadratically convergent CMCSCF method. To control the convergence to the correct CMCSCF stationary point, a modified step‐length control algorithm is introduced. Convergence to a tolerance of 1.0 × 10^?10 a.u. for the energy gradient is found to be typically within 10 iterations or less. A method involving the first block of the M matrix defined in the multiconfigurational spin tensor electron propagator method (MCSTEP) based on the CMCSCF reference state has been implemented to investigate ²P Be^? shape resonances. The position and width of these resonances have been calculated for different complete active space choices. The wide distribution of the position and width of the resonance reported in the literature is explained by the existence of two distinct resonances which are close in energy. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Synthesis and structure of a µ‐oxo diiron(III) complex with an N‐pyridylmethyl‐N,N‐bis(4‐methylbenzimidazol‐2‐yl)amine ligand and its catalytic property for hydrocarbon oxidation

A µ‐oxo diiron(III) complex [{Fe(pbba)Cl}₂(µ‐O)]Cl₂ (1, pbba = N‐pyridylmethyl‐N,N‐bis(4‐methylbenzimidazol‐2‐yl)amine) bearing multi‐imidazolyl motifs was synthesized and characterized by X‐ray crystallography to closely mimic the structural features of methane monooxygenase. As shown by its X‐ray crystal structure, complex 1 is a centrosymmetric dimer with an Fe? O? Fe angle of 180° , and pseudo‐octahedral around each iron(III) center. The catalytic ability of title compound in the oxidation of alkane and alkene is investigated by employing tert‐butylhydroperoxide and m‐chloroperbenzoic acid as oxidants under mild conditions. The catalytic oxidation results showed that radical intermediate dominates the oxidation process. Copyright © 2008 John Wiley & Sons, Ltd.     

A sensitive LC‐MS/MS method for simultaneous determination of R‐bambuterol and its active metabolite R‐terbutaline in human plasma and urine with application to a clinical pharmacokinetic study

A sensitive liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for simultaneous determination of R‐bambuterol and its active metabolite R‐terbutaline in human plasma and urine was established. The inhibition for the biotransformation of R‐bambuterol in plasma was fully investigated. Plasma samples were prepared on ice and neostigmine metilsulfate added as a cholinesterase inhibitor immediately after sample collection. All samples were extracted with ethyl acetate and separated on a C₁₈ column under gradient elution with a mobile phase consisting of methanol and water containing 5 mm ammonium acetate at a flow rate of 0.6 mL/min. The analytes were detected by an API 4000 tandem mass spectrometer with positive electrospray ionization in multiple reaction monitoring mode. The established method was highly sensitive with the lower limit of quantification (LLOQ) of 10.00 pg/mL for each analyte in plasma. In urine samples, the LLOQs were 20.00 and 500.0 pg/mL for R‐bambuterol and R‐terbutaline, respectively. The intra‐ and inter‐day precisions were <12.7 and <8.6% for plasma and urine, respectively. The analytical runtime within 6.0 min per sample made this method suitable for high‐throughput determination. The validated method has been successfully applied to the human pharmacokinetic study of R‐bambuterol involving 10 healthy volunteers. Copyright © 2013 John Wiley & Sons, Ltd.     

Iron(0), rhodium(I) and palladium(II) complexes with p‐(N,N‐dimethylaminophenyl) diphenylphosphine and the application of the palladium complex as a catalyst for the Suzuki–Miyaura cross‐coupling reaction

The reaction of p‐(N,N‐dimethylaminophenyl)diphenylphosphine [PPh₂(p‐C₆H₄NMe₂)] with [Fe₃(CO)₁₂], [Rh(CO)₂Cl]₂ and PdCl₂ resulted in three new mononuclear complexes, {Fe(CO)₄[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]} ( 1a ), trans‐{Rh(CO)Cl[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]₂} ( 2 ) and trans‐{PdCl₂[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]₂} ( 3 ), respectively. A small amount of dinuclear nonmetal‐metal bonded complex, {Fe₂(CO)₈[µ‐(P,N)‐PPh₂(p‐C₆H₄NMe₂)]} ( 1b ), was also isolated as a side product in the reaction of [Fe₃(CO)₁₂]. The complexes were characterized by elemental analyses, mass, IR, UV–vis, ¹H, ¹³C (except 1b) and ³¹P{¹H} NMR spectroscopy. The Pd complex 3 effectively catalyzes the Suzuki–Miyaura cross‐coupling reactions of aryl halides with arylboronic acids in water–isopropanol (1:1) at room temperature. Excellent yields (up to 99% isolated yield) were achieved. The effects of different solvents, bases, catalyst quantities were also evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

An LC‐MS/MS method for determination of curculigoside with anti‐osteoporotic activity in rat plasma and application to a pharmacokinetic study

A rapid, simple, selective and sensitive LC‐MS/MS method was developed for the determination of curculigoside in rat plasma. The analytical procedure involves extraction of curculigoside and syringin (internal standard, IS) from rat plasma with a one‐step extraction method by protein precipitation. The chromatographic resolution was performed on an Agilent XDB‐C₁₈ column (4.6 × 50 mm, 5 µm) using an isocratic mobile phase of methanol with 0.1% formic acid and H₂O with 0.1% formic acid (45:55, v/v) at a flow rate of 0.35 mL/min with a total run time of 2.0 min. The assay was achieved under the multiple‐reaction monitoring mode using positive electrospray ionization. Method validation was performed according to US Food and Drug Administration guidelines and the results met the acceptance criteria. The calibration curve was linear over 4.00–4000 ng/mL (R = 0.9984) for curculigoside with a lower limit of quantification of 4.00 ng/mL in rat plasma. The intra‐ and inter‐day precisions and accuracies were 3.5–4.6 and 0.7–9.1%, in rat plasma, respectively. The validated LC‐MS/MS method was successfully applied to a pharmacokinetic study of curculigoside in rats after a single intravenous and oral administration of 3.2 and 32 mg/kg. The absolute bioavailability of curculigoside after oral administration was 1.27%. Copyright © 2013 John Wiley & Sons, Ltd.     

Sensitive and precise HPLC method with back‐extraction clean‐up step for the determination of sildenafil in rat plasma and its application to a pharmacokinetic study

A sensitive HPLC method was developed and validated for the determination of sildenafil concentrations in rat plasma (200 μL) using a liquid–liquid extraction procedure and paroxetine as an internal standard. In order to eliminate interferences and improve the peak shape, a back‐extraction into an acidic solution was utilized. Chromatographic separation was achieved on a cyanopropyl bonded‐phase column with a mobile phase composed of 50 m m potassium dihydrogen phosphate buffer (pH 4.5) and acetonitrile (75:25, v/v), pumped at the flow rate of 1 mL/min. A UV detector was set at 230 nm. A calibration curve was constructed within a concentration range from 10 to 1500 ng/mL. The limit of detection was 5 ng/mL. The inter‐ and intra‐day precisions of the assay were in the ranges 2.91–7.33 and 2.61–6.18%, respectively, and the accuracies for inter‐ and intra‐day runs were within 0.14–3.92 and 0.44–2.96%, respectively. The recovery of sildenafil was 85.22 ± 4.54%. Tests confirmed the stability of sildenafil in plasma during three freeze–thaw cycles and during long‐term storage at ?20 and ?80°C for up to 2 months. The proposed method was successfully applied to a pharmacokinetic study in rats. Copyright © 2015 John Wiley & Sons, Ltd.     

Highly sensitive method for the determination of a novel triple kinase inhibitor with anti‐cancer activity,JI‐101, in rat plasma by liquid chromatography–electrospray ionization tandem mass spectrometry: application to a pharmacokinetic study

A highly sensitive, rapid assay method has been developed and validated for the estimation of JI‐101 in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. The assay procedure involves extraction of JI‐101 and phenacetin (internal standard, IS) from rat plasma with a solid‐phase extraction process. Chromatographic separation was achieved using a binary gradient using mobile phase A (acetonitrile) and B (0.2% formic acid in water) at a flow rate of 0.30 mL/min on a Prodigy ODS column with a total run time of 4.0 min. The MS/MS ion transitions monitored were 466.1 → 265 for JI‐101 and 180.1 → 110.1 for IS. Method validation and sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 5.03 ng/mL and the linearity range extended from 5.03 to 2014 ng/mL. The intra‐day and inter‐day precisions were in the ranges of 1.17–19.6 and 3.09–10.4%, respectively. This method has been applied to a pharmacokinetic study of JI‐101 in rats. Copyright © 2010 John Wiley & Sons, Ltd.     

An LC‐MS/MS method for determination of calceorioside B with cardiomyocyte protective activity in rat plasma and application to a pharmacokinetic study

A simple, sensitive and rapid liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the determination of calceorioside B (CLB) in rat plasma. Detection was performed on a Thermo Scientific Hypersil Gold chromatography column using isocratic elution with a mobile phase of methanol–5 m m ammonium acetate–formic acid (70:30:0.1, v/v/v). Mass spectrometry was performed in selection reaction monitoring mode using a positive electrospray ionization interface. Good linearity was found for CLB in plasma in the linear range of 1.00–500 ng/mL (r > 0.9960). The validated method was successfully applied to the pharmacokinetic study of CLB in rats. Copyright © 2015 John Wiley & Sons, Ltd.     

Highly sensitive method for the determination of ropinirole with a lower limit of quantitation of 3.45 pg/mL in human plasma by LC‐ESI‐MS/MS: application to a clinical pharmacokinetic study

A highly sensitive, rapid assay method has been developed and validated for the estimation of ropinirole (RPR) in human plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. A solid‐phase process was used to extract RPR and citalopram (internal standard, IS) from human plasma. Chromatographic separation was operated with 0.2% ammonia solution:acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a Hypurity C₁₈ column with a total run time of 3.2 min. The MS/MS ion transitions monitored were 261.2 → 114.2 for RPR and 325.1 → 209.0 for IS. Method validation and clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 3.45 pg/mL and the linearity was observed from 3.45 to 1200 pg/mL. The intra‐day and inter‐day precisions were in the range of 4.71–7.98 and 6.56–8.31%, respectively. This novel method has been applied to a pharmacokinetic study of RPR in humans. Copyright © 2008 John Wiley & Sons, Ltd.     

A high‐performance liquid chromatography–tandem mass spectrometry method coupled with protein precipitation for determination of granisetron in human plasma and its application to a comparative pharmacokinetic study

A rapid, simple and validated method based on liquid chromatography coupled with tandem mass spectrometry (LC‐MS/MS) has been developed for the determination of granisetron in human plasma. Plasma samples were pre‐purified by protein precipitation procedure. The chromatographic separation was achieved with Synergi Polar‐RP (75 × 2 mm, 4 µm) column using a mixture of 5 mm pH4.0 ammonium formate and methanol (300:316, v/v) under isocratic conditions at a flow rate of 0.3 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring mode using positive electrospray ionization. The analysis time was about 2.5 min. The method was fully validated over the concentration range 0.1–10 ng/mL. The lower limit of quantification was 0.1 ng/mL. Inter‐ and intra‐batch precision was <6.1% and the accuracy was within 95.6–100.0%. The mean extraction recovery was 96.3%. Selectivity, matrix effect and stability were also validated. The method was applied to the comparative pharmacokinetic study of granisetron in Chinese healthy subjects. Copyright © 2014 John Wiley & Sons, Ltd.     

A UFLC‐MS/MS method with a switching ionization mode for simultaneous quantitation of polygalaxanthone III,four ginsenosides and tumulosic acid in rat plasma: application to a comparative pharmacokinetic study in normal and Alzheimer's disease rats

A fast, sensitive and reliable ultra fast liquid chromatography‐tandem mass spectrometry (UFLC‐MS/MS) method has been developed and validated for simultaneous quantitation of polygalaxanthone III (POL), ginsenoside Rb1 (GRb1), ginsenoside Rd (GRd), ginsenoside Re (GRe), ginsenoside Rg1 (GRg1) and tumulosic acid (TUM) in rat plasma after oral administration of Kai‐Xin‐San, which plays an important role for the treatment of Alzheimer's disease (AD). The plasma samples were extracted by liquid–liquid extraction using ethyl acetate–isopropanol (1:1, v/v) with salidrdoside as internal standard (IS). Good chromatographic separation was achieved using gradient elution with the mobile phase consisting of methanol and 0.01% acetic acid in water. The tandem mass spectrometric detection was performed in multiple reaction monitoring mode on 4000Q UFLC‐MS/MS system with turbo ion spray source in a negative and positive switching ionization mode. The lower limits of quantification were 0.2–1.5 ng/ml for all the analytes. Both intra‐day and inter‐day precision and accuracy of analytes were well within acceptance criteria (±15%). The mean absolute extraction recoveries of analytes and IS from rat plasma were all more than 60.0%. The validated method has been successfully applied to comparing pharmacokinetic profiles of analytes in normal and AD rat plasma. The results indicated that no significant differences in pharmacokinetic parameters of GRe, GRg1 and TUM were observed between the two groups, while the absorption of POL and GRd in AD group were significantly higher than those in normal group; moreover, the GRb1 absorbed more rapidly in model group. The different characters of pharmacokinetics might be caused by pharmacological effects of the analytes. Copyright © 2013 John Wiley & Sons, Ltd.     

Development and application of a UPLC‐MS/MS method for simultaneous determination of fenofibric acid and berberine in rat plasma: application to the drug–drug pharmacokinetic interaction study of fenofibrate combined with berberine after oral administration in rats

With the purpose of carrying out pharmacokinetic interaction studies ofnberberine (BBR) and fenofibrate (FBT), an UPLC‐MS/MS method has been developed and validated. The analytes, BBR and fenofibric acid (FBA, metabolite of FBT) and the internal standard, tetrahydropalmatine, were extracted with dichloromethane–diethyl ether (3:2, v/v) and separated on an Agilent Eclipse XDB C₁₈ column using a mobile phase composed of acetonitrile and water. With positive ion electrospray ionization, the analytes were monitored on a triple quadrupole mass spectrometer in multiple reaction monitoring mode. Linear calibration curves were obtained over the concentration ranges of 0.1–100.0 ng/mL for BBR and 10.0–50,000.0 ng/mL for FBA. For BBR and FBA, the intra‐ and inter‐day precisions were <11.5 and 11.9%, respectively. The accuracy was within 11.7% and 11.3%. The mean recoveries of BBR at three concentrations of 0.2, 20.0, 80.0 ng/mL were >85.6%, and those of FBA at three concentrations of 20.0, 2500.0, 40,000.0 ng/mL were >87.9%. Consequently, the proposed method was applied to the pharmacokinetic interaction study of FBT combined with BBR after oral administration in rats and was proved to be sensitive, specific and reliable to analyze BBR and FBA in biological samples simultaneously. Copyright © 2016 John Wiley & Sons, Ltd.