摘要:

AbstractThe use of capillary electrophoresis/electrochemistry (CEEC) for the analysis of microdialysis samples obtained for pharmacokinetic and neurochemical studies is described, as well as the development of new types of electrodes and waveforms which increase the selectivity of this technique for specific classes of analytes. CEEC with a carbon fiber electrode was employed for the analysis of microdialysis samples. Microdialysis is anin vivosampling technique that yields very small samples for analysis (less than 1 μL). Therefore, capillary electrophoresis, with its small volume requirements, is an excellent choice for the analytical method. CEEC was used to study the pharmacokinetics ofL‐dopa and the release of aspartate and glutamate following a high K+infusion in the brain. Several modified electrodes which increase the applicability of CEEC in pharmaceutical and biomedical analysis are described. One of these is a gold/mercury electrode which is highly selective for thiols and was used for the determination of glutathione in a rat brain. An alternative method for the detection of thiols employed a chemically modified electrode containing cobalt phthalocyanine. In this case, an electrocatalyst reduces the overpotential of thiols at the carbon electrode and makes it possible to detect them at a much lower and more selective oxidation potential. This electrode was used for the detection of cysteine in urine. The development of pulsed amperometric detection for capillary electrophoresis is also described and is demonstrated by the detection of glucose in blood. Lastly, a method for the detection of peptides based on the formation of a copper complexs and detection at a carbon fiber electrode is discuss

ISSN:0173-0835    

DOI:10.1002/elps.1150150112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractUsing cyclodextrin micellar electrokinetic capillary chromatography (CD‐MECC), baseline separation of mephenytoin, 4‐hydroxymephenytoin and 4‐hydroxyphenytoin enantiomers in urine was effected with β‐cyclodextrin. After single‐dose administration of 100 mg of racemic mephenytoin, the 0–8 h urine was collected, and enzymatically hydrolyzed urine specimens were applied. For extensive metabolizers, a single peak for 4‐hydroxymephenytoin was detected corresponding to the S‐enantiomer. This peak was either very small or undectable in samples of poor metabolizers. Typically, mephenytoin could not be detected in these samples. However, application of undeglucu‐ronidated extracts revealed the presence of free S‐4‐hydroxymephenytoin and R,S‐mephenytoin and thus permitted phenotypingviaboth the urinary S:R enantiomeric ratio of mephenytoin and the hydroxylated metabolite. Application of enzymatically hydrolyzed and extracted urines after phenytoin administration (100 mg; 0–8 h urine collection) revealed the presence of S‐4‐hydroxyphenytoin. Thus, CD‐ MECC is shown to be a simple and attractive approach for (i) the confirmation of the stereoselectivity of the aromatic hydroxylation of mephenytoin and phenytoin, (ii) the simple and rapid differentiation between extensive and poor metabolizers for mephenytoin, an

ISSN:0173-0835    

DOI:10.1002/elps.1150150113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA simple, rapid, and quantitative capillary zone electrophoresis method for phenylalanine analysis in serum has been developed, with the aim of providing an analytical tool, as an alternative to liquid and gas chromatography, for the routine laboratory diagnosis of phenylketonuria. Electrophoresis was carried out in a 65 cm long, 50 μm wide bare silica capillary, using 0.025 M borate (adjusted to pH 10 with 1 M NaOH) at a potential of 20 kV, with in‐column UV detection at 214 nm. Under these conditions, the three aromatic amino acids (tryptophan, phenylalanine and tyrosine) migrated according to the pKs of the respective amine (and hydroxyl) groups. The efficiency of separation was about 150000 plates/column for phenylalanine. Diprophylline was adopted as internal standard. The injection of ethanoldeproteinized normal control serum gave rise to only a few major peaks not interfering with phenylalanine; phenylalanine in serum at normal concentrations appeared in a clean region of the electropherogram as a symmetrical peak with a migration time of about 11 min. The sensitivity was ≥ 3 μg/mL, with s/n ratio = 3. The linearity, in the range of 5–175 μg/mL, was described by the equationy1.407–0.583x,r2= 0.9998. Accuracy and precision were satisfactory, with intra‐day and inter‐day coefficients of variation lower than 4% and 7%, respectively. The injection of sera from five phenylketonuria patients gave electropherograms clearly showing huge peaks of phenylalanine, thus allowing an easy laboratory diagnosis of phenylketonuria.A preliminary version of this paper was presented at the 17th International Symposium on Column Liquid Chromatography, HPLC '93, Hamburg,

ISSN:0173-0835    

DOI:10.1002/elps.1150150114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe factors affecting micellar electrokinetic capillary chromatographic separation of hippuric ando‐,m‐,p‐methylhippuric acid were investigated by changing the species of micelles, and adding urea to the micellar solution. The analysis of hippurates in human urine is demonstrated under optimum conditions using 20 mMphosphate buffer (pH 8.0) containing 100 mMdodecyltrimethylammonium bromide and 4Murea at −22 kV applied voltage. This method proved suitable for the screening of hippurates in human urine following occupational exposure to toluene and

ISSN:0173-0835    

DOI:10.1002/elps.1150150115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA quantitative method for the determination of cocaine and related substances by micellar electrokinetic capillary chromatography (MECC) is described. Quantitative results obtained for both monitor materials and a number of actual drug seizures by this new capillary electrophoretic method are comparable to a gas chromatography (GC) run in parallel, both in the values and coefficient of variation achieved. The advantages of this new method include minimal use of solvents, the ability to readily automate the procedure and the ability to quantitate illicit heroin seizures under the same conditions with the exception of detector wavelength alteration. The method has proved rugged and reliable for both heroin and cocaine in a number of inter‐laboratory proficiency studie

ISSN:0173-0835    

DOI:10.1002/elps.1150150116

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0173-0835    

DOI:10.1002/elps.1150150117

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0173-0835    

DOI:10.1002/elps.1150150119

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA theory for field‐inversion gel electrophoresis of a flexible polyelectrolyte bearing an uncharged bulky label at one end is described, and the evolution of the mobility with chain length, field strength, friction of the label, and the duration of the forward and reverse pulses is predicted. A new critical size,Ndetrap, is introduced, and its value calculated. It increases roughly linearly with the duration of the reverse pulses. Chains smaller thanNdetrapare detrapped by reverse pulses, and may have a high mobility, whereas chains larger thanNdetrapare not trapped, and have a very small mobility. This leads to an increase of the mobility (as compared with constant field) in a given range of sizes, and to a strong selectivity aroundNdetrapDepending on the parameters, numerous other effects, including a secondary mobility plateau and band inversion, may appear. The corresponding regimes are predicted and discussed. All predictions are qualitatively consistent with available experimental data. We use them to suggest efficient conditions for the development of pulsed‐field trapping electrophoresis, a possible tool for improved DNA sequencing. In particular, we recommend using a ramping of pulse times, with a constant ratio of forward to reverse time in the range 3 t

ISSN:0173-0835    

DOI:10.1002/elps.1150150120

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractUsing a computer simulation algorithm based on the reptation model, we investigated the effects of pulsed field gel electrophoresis on the separation of single‐stranded DNA molecules in denaturing polyacrylamide gels. Pulsed fields that combine two different field intensities were found to affect the orientation of the reptation tube as well as the electrophoretic velocity, the rate of band broadening, the plate height and the molecular length for which the minimum of mobility was found, in agreement with available experimental results. Due to “memory” effects, pulses alternating between the forward and backward directions can reduce the diffusion constant by many orders of magnitude. Pulses of identical polarity but different intensities reduce the diffusion because stretches of less‐oriented DNA segments are conserved during the migration. We suggest that, for DNA sequencing, pulsed fields of fixed polarity should be used to reduce band broadening and not to overcome band inversion or suppress molecular orientation. We conclude that, using a low intensity, constant electric field will lead to smaller band widths than any pulsed field regime, in a similar length of experimental time, but with less compli

ISSN:0173-0835    

DOI:10.1002/elps.1150150121

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA procedure for the quantification of double‐strand breaks in yeast is presented that utilizes pulsed field gel electrophoresis (PFGE) and a comparison of the observed DNA mass distribution in the gel lanes with calculated distributions. Calculation of profiles is performed as follows. If double‐strand breaks are produced by sparsely ionizing radiation, one can assume that they are distributed randomly in the genome, and the resulting DNA mass distribution in molecular length can be predicted by means of a random breakage model. The input data for the computation of molecular length profiles are the breakage frequency per unit length, α, as adjustable parameter, and the molecular lengths of the intact chromosomes. The obtained DNA mass distributions in molecular length must then be transformed into distributions of DNA mass in migration distance. This requires a calibration of molecular lengthvs.migration distance that is specific for the gel lane in question. The computed profiles are then folded with a Lorentz distribution with adjusted spread parameter Γ to account for and broadening. The DNA profiles are calculated for different breakage frequencies α and for different values of Γ, and the parameters resulting in the best fit of the calculated to the observed profile are det

ISSN:0173-0835    

DOI:10.1002/elps.1150150122

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY