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1.
An optimized HPLC method for the quantification of metoclopramide (MCP) in human plasma and urine is described. MCP and internal standard are extracted from alkalinized substrate into diethyl ether and back-extracted into dilute acid. The analytes are separated with a ternary mobile phase at cyanopropyl-silica and detected at 312 nm (UV detection). The lower limit of quantification is 0.5 ng/ml in plasma and 50 ng/ml in urine. Optimization of extraction, chromatography, and detection is discussed. The method is selective to numerous common drug substances with excellent accuracy and precision data. After validation, the method is applied to the samples of a pharmacokinetic study. Pharmacokinetic parameters indicate the need for a sophisticated method as tool for optimization of metoclopramide formulations. 相似文献
2.
Jane S. Murray Pat Lane Anian Nieder Thomas M. Klapötke Peter Politzer 《Theoretical chemistry accounts》2010,127(4):345-354
Si-pentaerythritol tetranitrate (PETN), Si[CH2ONO2]4, is a silicon analog of the widely used explosive PETN, C[CH2ONO2]4. Si-PETN is extremely sensitive to impact, much more so than PETN. This was attributed by Liu et al. to Si-PETN having a
much lower activation barrier to decomposition, via a facile rearrangement that is not as readily available to PETN, and which
releases considerable energy that can promote further steps. We have investigated computationally why the barrier to the rearrangement
is so much lower for Si-PETN than for PETN, using 5, (H3C)3C–CH2ONO2, and 6, (H3C)3Si–CH2ONO2, as models for PETN and Si-PETN. Reaction force analysis shows that most of the difference between the rearrangement barriers
for 5 and 6 comes about in the initial (reactant) stages of the processes, in which 6 benefits from a 1,3 electrostatic interaction involving a positive σ–hole on the silicon and the negative linking oxygen.
The analogous interaction is weaker in 5, since the central carbon does not have positive σ–holes; furthermore, this carbon is less able than silicon to temporarily
expand its coordination sphere. A similar explanation involving a positive silicon σ–hole and a linking oxygen is proposed
for Si-PETN. The greater exothermicity of the rearrangement of 6 (and also Si-PETN) can be rationalized, following Liu et al., in terms of the formation of the strong Si–O bond. 相似文献
3.
The antidiabetic drug glibenclamide can be reliably quantitated in human serum with high performance liquid chromatography. The serum is buffered and extracted with toluene. The organic solvent is evaporated, the residue dissolved in the mobile phase and an aliquot sampled automatically and chromatographed. UV-detection at 229 m allows a lower limit of quantitation of 5 ng/ml. Precise handling of exact volumes facilitates external calibration. Statistical data for imprecision and inaccuracy are given and illustrate reliable quantification. Application of the method to experimental and clinical pharmacokinetic studies with specific problems is illustrated. 相似文献
4.
Nieder B Buus S Cazals Y Scharf B 《The Journal of the Acoustical Society of America》2007,122(1):35-37
The induced reduction in the loudness (ILR) of a weaker tone caused by a preceding stronger tone was measured with both tones in the same ear (ipsilateral ILR) and also in opposite ears (contralateral ILR). The two tones were always equal in duration and were presented repeatedly over several minutes. When the tone duration was 200 ms, for 24 listeners the loudness reduction averaged 11 dB under ipsilateral ILR and 6 dB under contralateral ILR. When the duration was 5 ms, ILR was 8 dB whether ipsilateral or contralateral. For each duration, ipsilateral and contralateral ILR were strongly correlated (r around 0.80). 相似文献
5.
Work-up procedures and HPLC separation systems for determination of taurocholic, glycocholic, chenodeoxycholic, and cholic acids and lysolecithin in artificial and natural gastric juice are described. These compounds are used for testing the binding capacity of antacida to the individual analytes. Work-up is simple, no extraction or filtration being required. The optimized combinations of stationary and mobile phases allow selective and sensitive determination of the respective bile acids in gastric juice. For optimization, the capacity factors of two related bile acids were evaluated for numerous commercial stationary phases. The mechanism of retention is different for free and conjugated bile acids. Special aspects of routine analysis are discussed. 相似文献
6.
The bronchosecretolytic drug ambroxol can be reliably quantified in human plasma by high performance liquid chromatography. Plasma is buffered alkaline, extracted with ether, and the organic solvent back-extracted with diluted acid. An automatically sampled aliquot is separated by reversed phase HPLC; the analyte is well separated from two metabolites that interfered strongly in earlier methods. UV detection at 230 nm enables a lower limit of quantitation of 5 ng/ml. Internal standardization with propranolol allows accurate and precise quantification. Evaluation of the optimized combination of mobile and stationary phase is described, and application of the method to experimental and clinical pharmacokinetic studies is illustrated. 相似文献
7.
The antihypertensive agent urapidil (Ebrantil Byk-Gulden, Konstanz) can be reliably quantitated with three metabolites in human serum using high performance liquid chromatography. Serum is alkalinized and extracted with ethyl acetate. The organic phase is back-extracted with diluted acid. An aliquot is sampled automatically and chromatographed in an optimized combination of mobile and stationary phase. UV-detection at 273 nm allows a quantitation limit of 5 ng/ml for all analytes. Precise handling of exact volumes facilitates external calibration. The coefficient of variation for spiked samples is less than 5% within and less than 7% between studies. Application of the method to experimental and clinical pharmacokinetic studies of urapidil is illustrated. 相似文献
8.
Summary A method for the selective quantification of doxycycline in human plasma and urine has been developed using HPLC with UV-detection
at 350 nm. Analyte and internal standard were extracted from plasma by extraction columns filled with octadecylsilica. Urines
were only mixed with diluted acid prio to injection. The influence of pH on peak shapes is discussed as well as comparative
investigations on selectivity and peak symmetry on commerical octadecylsilica. The method was successfully applied to the
samples of a clinical study with an oral single dose of 100 mg. Precision and accuracydata of the assay and calculated pharmacokinetic
parameters are presented. 相似文献
9.
10.
Sensitive quantification of pseudoephedrine in human plasma and urine by high-performance liquid chromatography 总被引:4,自引:0,他引:4
An assay for the selective quantification of pseudoephedrine in human plasma and urine was developed using high-performance liquid chromatography with UV detection at 205 nm. Analyte and internal standard were extracted from alkaline plasma or urine into a mixture of n-hexane and diethyl ether, and the organic phase was back-extracted into dilute acid. The chromatographic system comprises microparticulate cyanopropyl-silica as stationary phase and a ternary solvent mixture with ion-pair reagents as mobile phase. Using 0.25 ml plasma, the lower limit of quantification was 25 ng/ml with excellent linearity up to 1000 ng/ml. In urine, the calibration ranged from 2.5 to 100 micrograms/ml. The selectivity of the method was demonstrated for several pharmaceuticals with similar structures. The validated method was applied to a pharmacokinetic study with a single oral dose of 100 mg of pseudoephedrine in two galenic formulations. Precision and accuracy data of the assay and calculated pharmacokinetic parameters are presented. 相似文献