Journal of capillary electrophoresis and microchip technology最新文献

In order to speed up the trial-and-error process during enantioselective capillary electrophoresis methods development, a systemized approach is proposed to develop methods by applying several screening methods in the search for an initial separation. Screening methods combine high selectivity with broad applicability and are applied to find an initial enantiomeric separation during early pharmaceutical development (pre-Phase 1 to Phase 1). The goal is to achieve enantiomeric separation rapidly in order to characterize the chiral purity of pharmaceutical products. Dedicated, highly efficient screening methods are suggested for basic, neutral, and acidic compounds. In these screening methods, multiple chiral selectors are applied in mixtures at different buffer pH values. For the compounds studied, the technique allows fast method development. Furthermore, it is potentially applicable to a wide range of low-molecular-weight compounds and permits rapid analysis at low cost, since runs are performed in inexpensive, bare silica capillaries using ordinary buffer systems with only typical cyclodextrins as the selector. Along with simplicity and robustness, the approach results in sufficient efficacy (i.e., it is easy, straightforward, and reproducible, with a high success rate). Typical pharmaceutical applications are described. The major advantage of the screening approach to methods development is the decrease in development cycle time. The total screening time for one compound was about 5.3 hr on one CE instrument.

This work presents a comparative evaluation of extraction procedures for the capillary analysis of seven opiates (meperidine, morphine, naloxone, tramadol, fentanyl, sufentanyl, and alfentanyl) in human hair. Pieces of hair (50-150 mg) were subjected to acidic hydrolysis (0.25 mmol L(-1) HCl at 45 degrees C, overnight) followed by pH adjustment and either liquid-liquid extraction (LLE) in hexane, petroleum ether, dichloromethane, and ethyl acetate solvents, or solid-phase extraction (SPE) in octadecyl, cyanopropyl, and aminopropyl bonded silica and cation exchange polymeric phases. Excellent recoveries of approximately 70% (naloxone and fentanyl and its analogues), 88% (meperidine), and ca. 100% (morphine and tramadol) were obtained using SPE in a M-fixed-mode cation exchange reversed-phase cartridge (Oasis MCX LP, Waters Corp., Milford, MA, U.S.A.), making this type of procedure eligible for novel clinical and forensic methodologies for hair analysis. The utility of the proposed extraction technique was demonstrated by the analysis of hair extracts from patients using morphine as part of their pain management protocol.

Easy applicability of modern microfabrication technology to electrophoresis microchips has initiated a rapidly moving interdisciplinary field in analytical chemistry. Electric field-mediated separations in microfabricated devices are significantly faster than conventional electrophoresis methods and are usually completed in seconds to minutes. The flexibility of fluidic manipulations in electrophoresis microchips allows the use of a variety of separation techniques and conditions. In this study, large-scale genotyping of the repeat polymorphism in the regulatory (promoter) region of the serotonin transporter gene 5-HTT linked polymorphic region (5-HTTLPR) was attempted using polymerase chain reaction (PCR) amplification followed by rapid microchip electrophoresis analysis of the amplicons.

A method for the separation and quantification of aristolochic acids by capillary electrophoresis is described. Buffer solutions composed of sodium dihydrogen phosphate, sodium borate, and sodium dodecyl sulfate at pH 6.5-7 were found to be suitable for the separation of aristolochic acids, which can be well resolved in a few minutes. The separation and identification of six aristolochic acids contained in a commercial tincture called charrua, a traditional herbal medicine consisting of a hydroalcoholic extract of Aristolochia argentina, corroborate the usefulness of the method. The eventual toxic properties of the aristolochic acid containing charrua tincture are discussed.

This article evaluates the potential of using fiber optics as a detection tool during electrophoretic separations or identification and quantification of analytes in miniaturized systems, including microchips. This paper covers reports in the literature from 1989 to June 2002. The articles have been chosen based on various aspects of the instrumentation including the microchip substrates, channel size and geometry, pathlength, fiber and detector types, light source, separation conditions, detection limits, and applications-all with the goal of comparing and contrasting optical detections. This review has been divided into three groups: fluorescence measurement-based studies, absorbance measurement-based studies, and innovative studies in chronological order.

The combined use of an in-tube enzyme assay and capillary electrophoresis for determining beta-hydroxyacyl CoA-dehydrogenase (beta-HADH) activity in meat was investigated. Beta-HADH is a significant mitochondrial enzyme in food muscle; thus, the determination of its activity is important in food analysis. The enzymatic assay and the separation of the reaction products were carried out by electrophoretically mediated microanalysis (EMMA) using a plug-plug reaction mode at variable potential. For the quantification of beta-HADH activity, the rate of conversion of reduced beta-nicotinamide adenine dinucleotide (NADH) to beta-nicotinamide adenine dinucleotide (NAD+) was calculated by determining NAD+ at 260 nm. A calibration curve for NAD+ concentration versus normalized areas showed a highly significant (p < 0.001) linear relationship (R2 = 0.993). Accurate quantification of beta-HADH activity was achieved since on-line monitoring allowed us to account for the NAD+ produced from NADH degradation by applying a correction factor. An average reaction time of 0.66 +/- 0.06 sec was determined for a protein concentration in the range of 0.1-0.5 mg protein/mL. The assay was reproducible since coefficients of variation of less than 6.2% were calculated for triplicate analyses.

High-performance liquid chromatography is usually used to assay the main compound and organic impurity content of drug substance and drug product during pharmaceutical development. A crucial validation parameter of these methods is specificity--the ability to unequivocally assess the analyte in the presence of component expected to be present. Typically, these include impurities, degradation products, and matrices. Besides adequate chromatographic separation with sufficient selectivity, additional 2- or 3-D spectroscopic or chromatographic tools are frequently necessary for this purpose. In our current practice, HPLC is used with ultraviolet photodiode array detection and on-line mass spectrometry (LC-UVDAD-MS) during the assessment of specificity. Although this approach is very powerful and can solve the majority of problems, separation of isomers of the main compound is still difficult. Since HPLC usually cannot offer the required selectivity and because of the similar molecular weights, structural isomers are not specifically detected using LC-MS. Capillary electrophoresis, on the other hand, offers high separation efficiency and can be applied as an adjunct to HPLC. Therefore, a set of highly selective CE methods is used orthogonally in the specificity assessment of HPLC methods.

The last few years have seen a growing interest in the study of the sources and metabolism of isoflavones due to their potential role in the prevention and treatment of chronic disease (i.e., coronary artery disease, osteoporosis, and certain types of cancer). Furthermore, isoflavonoids have reportedly been instrumental in relieving menopausal symptoms (i.e., hot flashes, night sweats, other vasomotor symptoms, and bone loss). Isoflavonoids are compounds that occur naturally in plants and belong to the phytoestrogen family, as do coumestans and lignans. There is much to learn about the effects of isoflavonoids and their potential health benefits; thus they are researched extensively through molecular, preclinical, and clinical studies. Capillary zone electrophoresis (CZE) was explored as a new tool for characterizing the content of isoflavonoids in the urine of subjects who consume large amounts of soy and derivative products. The effect of pH, buffer concentration, and instrument parameters on the migration behavior of these products was studied. Due to the phenolic nature of isoflavonoids, alkaline pHs (8.20-9.90) were tested. The influence of electrolyte concentration in the 50-250 mM range on migration times and resolution was researched. Solid-phase extraction (SPE) was carried out for sample cleanup and preconcentration.

Histones are the most intensively studied group of basic nuclear proteins and are of great importance with regard to the organization of chromatin structure and control of gene activity. The complexity of this protein family places very high demands on the analytical methods applied. The advent of high-performance capillary electrophoresis provided a promising new tool for their separation, which is an essential prerequisite for studying the biological role of this protein family. Problems inherent to histone analysis due to their unique physical and chemical properties are reviewed, and the pros and cons of distinct strategies developed for CE separation of these proteins are discussed.