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Choei Wakasugi – One of the best experts on this subject based on the ideXlab platform.

Keizo Sato – One of the best experts on this subject based on the ideXlab platform.

  • High-throughput determination of barbiturates in human plasma using on-line column-switching ultra-fast liquid chromatography–tandem mass spectrometry
    Forensic Toxicology, 2013
    Co-Authors: Xiao-pen Lee, Takeshi Kumazawa, Chika Hasegawa, Tetsuya Arinobu, Hiroshi Seno, Osamu Suzuki, Keizo Sato

    A high-throughput method was developed for determinations of eight barbiturates (barbital, Allobarbital, phenobarbital, cyclobarbital, amobarbital, secobarbital, thiopental, and thiamylal) in human plasma by on-line column-switching ultra-fast liquid chrochromatography–tandem mass spectrometry (MS–MS). Plasma samples (100 μl) spiked with the eight barbiturates and 5-(4-methylphenyl)-5-phenylhydantoin (internal standard) were diluted with 300 μl of 13.3 mM ammonium acetate/acetonitrile (33:67, v/v). After centrifugation and filtration, the clear supernatant was injected directly onto the extraction column (Oasis HLB cartridge column). The following procedure was fully automated. The analytes retained on the extraction column were eluted by backflushing of the extraction column and introduced onto the analytical column (Phenomenex Onyx monolithic C_18 column, 100 mm × 4.6 mm i.d.) by column switching. Quantification was performed by multiple reaction monitoring with negative-ion atmospheric pressure chemical ionization. Good peak separation and peak shapes of the eight drugs were achieved within an analysis time of 3 min, including the extraction time. All drugs spiked into plasma showed recoveries of 80–93 %. The regression equations for the eight drugs showed excellent linearities in the range of 10–5000 ng/ml of plasma, and the limits of detection ranged from 1.0 to 10 ng/ml. The lower and upper limits of quantitation were 10–50 ng/ml and 5000 ng/ml, respectively. Intraday and interday coefficients of variation for all the drugs were not >9.1 %. The accuracies of quantitation were 92.0–108 %. The method was successfully applied to determination of the level of amobarbital in human plasma after its oral administration to a volunteer.

Youwen Tang – One of the best experts on this subject based on the ideXlab platform.

Ronald A Lubet – One of the best experts on this subject based on the ideXlab platform.

  • enhancement of hepatocarcinogenesis and induction of specific cytochrome p450 dependent monooxygenase activities by the barbiturates Allobarbital aprobarbital pentobarbital secobarbital and 5 phenyl and 5 ethylbarbituric acids
    Carcinogenesis, 1994
    Co-Authors: Jerry M Ice, Bhalchandra A Diwan, Jerrold M Ward, Raymond W Nims, Ronald A Lubet

    To test predictions that barbiturates which are long-acting sedatives and/or strong inducers of CYP2B-mediated monooxygenase activities would be effective promoters of hepatocarcinogenesis, a series of clinically-useful barbiturates and structural analogs were tested for ability to promote hepatocellular carcinogenesis in male F344/NCr rats initiated with N-nitrosodiethylamine and for efficacy as inducers of CYP2B activity in non-initiated rats of the same sex and strain. The barbiturates were administered in the diet at concentrations equimolar to 500 p.p.m. of the known liver tumor promoter phenobarbital, which served as the positive control for this study. Phenobarbital, which has the longest duration of sedative action of this series of compounds, caused the greatest induction of CYP2B activity, and displayed strong liver tumor promoting effects. Allobarbital and aprobarbital, two intermediate-duration sedatives, were found to promote hepatocarcinogenesis, with Allobarbital proving to be as effective as phenobarbital in this respect and aprobarbital being somewhat weaker as a promoter. These intermediate-duration sedatives were each relatively weak CYP2B-type inducers, causing approximately 25% of the induction displayed by phenobarbital. The nonsedatives, 5-phenyl- and 5-ethyl-barbituric acids, were essentially inactive as CYP2B-type inducers and were also found to be relatively inactive as promoters of hepatocarcinogenesis. Of the shorter-duration sedatives, pentobarbital was found to promote, and was relatively effective as a CYP2B-type inducer, while secobarbital showed little or no promoting activity and was less effective as an inducer of CYP2B activities. Pentobarbital thus proved an important exception to our hypothesis that only long-acting sedative barbiturates would promote hepatocarcinogenesis. Although both the durations of sedative action and the degrees of CYP2B-type induction exhibited by these compounds correlate with a quantitative parameter for liver tumor-promoting activity (relative promotion index), neither parameter appears to be sufficient, by itself, as a predictor of promoting activity for rat liver.

Jia-ping Lai – One of the best experts on this subject based on the ideXlab platform.

  • Recognition characteristics of molecularly imprinted microspheres for triazine herbicides using hydrogen-bond array strategy and their analytical applications for corn and soil samples.
    Journal of chromatography. A, 2011
    Co-Authors: Qionghui Yuan, Youwen Tang, Xiongjun Zuo, Jia-ping Lai

    The homogeneous molecularly imprinted microspheres (MIMs) based on a biologically inspired hydrogen-bond array were prepared using Allobarbital as the novel functional monomer and divinylbenzene as the cross-linker. The host-guest binding characteristics were examined by molecular simulation and infrared spectroscopy. The resultant MIMs were evaluated using high performance liquid chromatography and solid-phase extraction. The results obtained demonstrate that the good imprinting effect and the excellent selectivity of MIMs are mainly due to the interaction involving the formation of three-point hydrogen bond between host and guest. The complete baseline separation was obtained for five triazine analogues and a metabolite on the MIM HPLC column. The MIMs were further successfully used as a specific sorbent for selective extraction of simetryne from corn and soil samples by molecularly imprinted solid phase extraction. Detection limits and recoveries were 5.8 μg/kg and 0.14 μg/kg and 87.4-105% and 94.6-101% for simetryne in corn and soil sample, respectively.