Review of recent advances in analytical techniques for the determination of neurotransmitters

This review covers recent advances of capillary electrophoresis (CE) in pharmaceutical analysis. The principle, instrumentation, and conventional modes of CE are briefly discussed. Advances in the different CE techniques (non-aqueous CE, microemulsion electrokinetic chromatography, capillary isotachophoresis, capillary electrochromatography, and immunoaffinity CE), detection techniques (mass spectrometry, light-emitting diode, fluorescence, chemiluminescence, and contactless conductivity), on-line sample pretreatment (flow injection) and chiral separation are described. Applications of CE to assay of active pharmaceutical ingredients (APIs), drug impurity testing, chiral drug separation, and determination of APIs in biological fluids published from 2008 to 2009 are tabulated.

Recent advances of capillary electrophoresis in pharmaceutical analysis

The electro-oxidation of dopamine (DA) is investigated on the unmodified surfaces of five different classes of carbon electrodes: glassy carbon (GC), oxygen-terminated polycrystalline boron-doped diamond (pBDD), edge plane pyrolytic graphite (EPPG), basal plane pyrolytic graphite (BPPG), and the basal surface of highly oriented pyrolytic graphite (HOPG), encompassing five distinct grades with step edge density and coverage varying by more than 2 orders of magnitude. Surfaces were prepared carefully and characterized by a range of techniques, including atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and Raman spectroscopy. Although pBDD was found to be the least susceptible to surface fouling (even at relatively high DA concentrations), the reaction showed sluggish kinetics on this electrode. In contrast, DA electro-oxidation at pristine basal plane HOPG at concentrations ≤100 μM in 0.15 M PBS, pH 7.2, showed fast kinetics and only minor susceptibility toward surface fo...

Comparison and reappraisal of carbon electrodes for the voltammetric detection of dopamine.

Electropolymerized film of functionalized thiadiazole on glassy carbon electrode for the simultaneous determination of ascorbic acid, dopamine and uric acid.

This contribution is a methodological review of the publications about the topic from the last 2 years. Therefore, it is primarily organized according to the methods and procedures used in surveyed papers and the origin and type of sample and specification of analytes form the secondary structure. The introductory part about navigation in the architecture of stacking brings a brief characterization of the various stacking methods, with the description of mutual links to each other and important differences among them. The main body of the article brings a survey of publications organized according to main principles of stacking and then according to the origin and type of the sample. Provided that the paper cited gave explicitly the relevant data, information about the BGE(s) used, procedure, detector employed, and reached LOD and/or concentration effect is given. The papers where the procedure used is a combination of diverse fragments and parts of various stacking techniques are mentioned in a special section on combined techniques. The concluding remarks in the final part of the review evaluate present state of art and the trends of sample stacking in CE.

Contemporary sample stacking in analytical electrophoresis

Determination of dopamine in the presence of ascorbic acid using poly(3,5-dihydroxy benzoic acid) film modified electrode.

A rapid capillary electrophoresis method based on online acid barrage stacking has been successfully established for analysis of trace amounts of genistein in human plasma. Genistein was analyzed within 8 min, with 200 mmol L−1 citric acid (pH 1.7) as acid barrage, and injection times of 180 and 30 s for sample and acid, respectively. Good linearity was obtained in the range 0.05–5 mg L−1 and the limit of detection was 0.03 mg L−1. Compared with normal sample injection, this method resulted in more than a fiftyfold improvement in detection sensitivity. The technique has potential for use in studies of genistein metabolism and of exposure levels in humans.

Hai-Yan Feng

Papers

Determination of dopamine in the presence of ascorbic acid using poly(3,5-dihydroxy benzoic acid) film modified electrode.

Quantitative Analysis of Genistein in Human Plasma by Online Concentration CE with UV Detection