Simultaneous determination of antiviral drugs in chicken tissues by ultra high performance liquid chromatography with tandem mass spectrometry

An ultra high performance liquid chromatography with tandem mass spectrometry method was established for the rapid and simultaneous analysis of seven antiviral drugs, amantadine, rimantadine, memantine, moroxydine, imiquimod, oseltamivir, and acyclovir, in chicken liver, muscle, and egg. Homogenized samples were extracted with trichloroacetic acid and acetonitrile solutions and then purified by cation‐exchange solid‐phase extraction. The target drugs were analyzed by liquid chromatography with a UPLC BEH Amide column (2.1 mm × 100 mm, 1.7 μm) coupled with a tandem mass spectrometer operating in the positive multiple‐reaction mode. A perfectly linear relationship was obtained within the concentration ranges of 0.5–20 μg/L for acyclovir and 0.1–10 μg/L for the other six antiviral drugs. The average recoveries of the seven antiviral drugs using four addition levels in chicken liver, muscle, and eggs were 82.67–90.10, 82.30–92.27, and 81.98–93.77%, respectively, and the acceptable coefficients of variation were 5.18–9.88, 4.84–11.2, and 42.8–9.95%, respectively. The detection limits and detection capabilities of the analysis method for the seven antiviral drugs were in the ranges of 0.04–0.64 and 0.11–0.78 μg/kg, respectively. Additionally, an inter‐laboratory study among five laboratories further validated the method.     

关于群布尔矩阵的收敛和周期

在文[1]和[2]中,各自得到了如下结果：一个循环布尔矩阵A是本原的当且仅当gcd（i2-i1,…,i1-i1,n）＝1,其中A＝Pi1十Pi2十…＋Pi1,0≤i1＜i2＜…＜i1≤n-1,P是对应于n阶循环置换（123…n）的置换矩阵．在本文中,先把此结果推广到群矩阵（一种循环矩阵的推广）．其次,讨论群布尔矩阵的周期．给出了计算周期的算法,最后,探讨循环布尔矩阵A的使Am p＝Am的最小正整数m.     

Vapour–liquid equilibrium for the systems diethyl sulphide + 1-butene, +cis-2-butene, +2-methylpropane, +2-methylpropene, +n-butane, +trans-2-butene

Isothermal vapour–liquid equilibrium was measured for the systems of diethyl sulphide + 1-butene, +cis-2-butene, and +2-methylpropene at 312.6 K, diethyl sulphide + n-butane was measured at 317.6 K, diethyl sulphide + trans-2-butene at 317.5 K, and diethyl sulphide + 2-methylpropane at 308.0 K. The pressure–temperature–total composition data were converted into pressure–temperature–liquid–vapour composition data using the method of Barker. Error estimates are provided for each variable. The isothermal parameters for the Wilson, NRTL and UNIQUAC activity coefficient models were regressed. The measurements were compared with the predictions by COSMO segment activity coefficient (COSMO-SAC) and UNIFAC.     

求解非凸区域上凸函数比式和问题的全局优化方法

针对非凸区域上的凸函数比式和问题,给出一种求其全局最优解的确定性方法.该方法基于分支定界框架.首先通过引入变量,将原问题等价转化为d.c.规划问题,然后利用次梯度和凸包络构造松弛线性规划问题,从而将关键的估计下界问题转化为一系列线性规划问题,这些线性规划易于求解而且规模不变,更容易编程实现和应用到实际中;分支采用单纯形对分不但保证其穷举性,而且使得线性规划规模更小.理论分析和数值实验表明所提出的算法可行有效.     

Aryl-diamide bridged binuclear ruthenium (II) tris(bipyridine) complexes: Synthesis, photophysical, electrochemical and electrochemiluminescence properties

Several new symmetrical aromatic hydrocarbon bridged bipyridine ligands and their binuclear Ru (II) complexes have been designed, synthesized and characterized on the basis of ¹H NMR, MS and HRMS. Their absorption and emission properties, electrochemical behaviors and electrochemical luminescence were investigated. All ruthenium complexes show characteristic MLCT absorption and similar redox potential. Among the three complexes reported, 4c has the best electrochemical luminescence property.     

Steroid and steroid glucuronide profiles in urine during pregnancy determined by liquid chromatography–electrospray ionization-tandem mass spectrometry

An ultra performance liquid chromatography–electrospray ionization-tandem mass spectrometry (UPLC–MS/MS) method was developed for the analysis of steroids and their glucuronides in urine samples. The method provides high sensitivity and fast analysis, as both steroids and their glucuronides can be analyzed directly without hydrolysis or complex sample preparation. The method was applied in profiling of targeted and nontargeted steroids and steroid glucuronides during pregnancy. The concentrations of 11 of 27 targeted steroids and steroid glucuronides and the concentrations of 25 nontargeted steroid glucuronides increased about 10–400 fold during the pregnancy. The concentrations of most of these 36 compounds began to increase in the first days of the pregnancy, increased gradually during the pregnancy, achieved a maximum in late pregnancy, and decreased sharply after delivery. Exceptionally, the concentrations of allopregnanolone and 17-hydroxypregnenolone started to increase later than those of the other steroids. Moreover, the concentrations of E2 glucuronides began to decrease one week before the delivery, in contrast to most of the steroids and steroid glucuronides, whose concentrations dropped sharply during the delivery. Concentrations of 34 compounds decreased noticeably when the subject was on sick leave owing a series of painful contractions. The results suggest that steroids and especially steroid glucuronides may provide a valuable diagnostic tool to follow the course of pregnancy.     

Fingerprinting the degradation product patterns of different polyester‐ether networks by electrospray ionization mass spectrometry

Fingerprinting of the degradation product patterns by electrospray ionization mass spectrometry (ESI‐MS) was evaluated as a tool to monitor the degree of degradation in polyester‐ether networks. Four different crosslinked caprolactone (CL) and/or 1,5‐dioxepan‐2‐one (DXO) networks were subjected to hydrolytic degradation in aqueous solution at 37 °C for up to 147 days. After predetermined time periods, the water‐soluble degradation products were analyzed by ESI‐MS and tandem ESI‐MS. In addition, changes in pH, mass loss, and copolymer composition were determined. In the case of more slowly hydrolyzed CL‐rich (co)polymers, CL and/or DXO oligomers terminated by hydroxyl and carboxyl end groups were predominantly formed as degradation products. However, on prolonged hydrolysis oligomers with attached crosslinking agent dominated the degradation product patterns of more easily hydrolyzed DXO‐rich (co)polymers. It was shown that in the recorded mass spectra the variation of intensities in the series of ions corresponding to DXO and CL/DXO oligomers with or without attached crosslinking agent could be utilized to monitor the extent of hydrolytic degradation in the polyester matrix and the disruption of the network structure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4617–4629, 2008     

Identification of bupropion urinary metabolites by liquid chromatography/mass spectrometry

Human urinary metabolism of the antidepressant bupropion was studied using liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). A total of 20 metabolites were detected and identified. The phase I metabolism included formation of morpholinohydroxybupropion, threo- and erythrohydrobupropion, aromatic hydroxylation, butyl group hydroxylation with ketone hydrogenation and dihydroxylation. These metabolites were detected either as the free form or as glucuronide and/or sulphate conjugates. In addition also m-chlorohippuric acid was detected. Of the phase I metabolites, a dihydroxylation to the aromatic ring and to the methyl group in the middle of the substrate molecule was reported here for the first time, as well as eight of the glucuronide conjugates (to hydroxy, dihydroxy, hydroxy and hydrogenation metabolites) and three of the sulphate conjugates (to aromatic hydroxy and hydroxy and hydrogenation metabolites).     

In vitro interaction cocktail assay for nine major cytochrome P450 enzymes with 13 probe reactions and a single LC/MSMS run: analytical validation and testing with monoclonal anti-CYP antibodies

A sensitive and rugged LC/MSMS method was developed for a comprehensive in vitro metabolic interaction screening assay with N-in-1 approach reported earlier. A cocktail consisting of ten cytochrome P450 (CYP)-selective probe substrates with known kinetic, metabolic and interaction properties in vivo was incubated in a pool of human liver microsomes, and metabolites of melatonin (CYP1A2), coumarin (CYP2A6), bupropion (CYP2B6), amodiaquine (CYP2C8) tolbutamide (CYP2C9), omeprazole (CYP2C19 and CYP3A4), dextromethorphan (CYP2D6), chlorzoxazone (CYP2E1), midazolam (CYP3A4) and testosterone (CYP3A4) were simultaneously analysed with a single LC/MSMS run. Altogether, 13 metabolites and internal standard phenacetin were analysed in multiple reaction mode. Polarity switching mode was utilized to acquire negative ion mode electrospray data for hydroxychlorzoxazone and positive ionization data for the rest of the analytes. Fast gradient elution was applied, giving total injection cycle of 8 min. The method was modified for two different LC/MSMS systems, and was validated for linear range, detection limit, accuracy and precision for each metabolite. In addition, cocktail inhibition system was further tested using monoclonal anti-CYP antibodies as inhibitors for each probe reaction.