The presented study aims to develop a new online enrichment strategy [“pseudostationary ion-exchanger” (PSIE) sweeping] for the analysis of highly hydrophilic nucleosides in urine samples with a special focus on the fundamental aspects regarding the enrichment process itself. In the first method, we employ the ionic liquid (IL)-type surfactant 1-tetradecyl-3-methylimidazolium bromide (C14MImBr) as micelle forming agent under alkaline pH conditions. It is shown that maximum enrichment efficiency can be obtained by keeping the retention factors very high within the sample zone and very low within the background electrolyte (BGE) while maintaining a sufficient resolution for the studied analytes. With this method, detection limits as low as 0.1 µg mL−1 are obtained for all analytes studied. For the nucleosides, adenosine and cytidine, a second method is developed using sodium dodecyl sulfate (SDS) as micelle forming agent under acidic pH conditions. In addition, we investigate the effect of replacing ionic buffering constituents with a zwitterionic/isoelectric buffering compound (aspartic acid) with regard to separation and enrichment efficiency. With the second method, the achieved limits of detection are as low as 0.1 µg mL−1 for Ado and 0.2 µg mL–1 for Cyd. The applicability of the two complementary methods to the analysis of the nucleosides under investigation is shown for blank and spiked human urine samples after their extraction using the commercially available phenylboronate affinity gel.

In the last few decades, many new antiepileptic drugs came out to medicine world, and their use was expanded over a wide range of cases. Analysts from all over the world developed many different separation methods for the determination of these drugs in a quantitative way either in pharmaceutical dosage forms or in biological fluids. In this review article, a summation of previously published separation methods including high-performance thin-layer chromatography, high-performance liquid chromatography, gas chromatography, and electrophoresis used for the determination of eslicarbazepine acetate, levetiracetam, lacosamide, oxcarbazepine, pregabalin, and retigabine are presented. These six drugs are the most commonly used drugs for the treatment of patients diagnosed with partial onset seizures. This article can help researchers and analysts to build upon this knowledge and add further methods of analysis in the future.

In the last few decades, many new antiepileptic drugs came out to medicine world, and their use was expanded over a wide range of cases. Analysts from all over the world developed many different separation methods for the determination of these drugs in a quantitative way either in pharmaceutical dosage forms or in biological fluids. In this review article, a summation of previously published separation methods including high-performance thin-layer chromatography, high-performance liquid chromatography, gas chromatography, and electrophoresis used for the determination of eslicarbazepine acetate, levetiracetam, lacosamide, oxcarbazepine, pregabalin, and retigabine are presented. These six drugs are the most commonly used drugs for the treatment of patients diagnosed with partial onset seizures. This article can help researchers and analysts to build upon this knowledge and add further methods of analysis in the future.

In the last few decades, many new antiepileptic drugs came out to medicine world, and their use was expanded over a wide range of cases. Analysts from all over the world developed many different separation methods for the determination of these drugs in a quantitative way either in pharmaceutical dosage forms or in biological fluids. In this review article, a summation of previously published separation methods including high-performance thin-layer chromatography, high-performance liquid chromatography, gas chromatography, and electrophoresis used for the determination of eslicarbazepine acetate, levetiracetam, lacosamide, oxcarbazepine, pregabalin, and retigabine are presented. These six drugs are the most commonly used drugs for the treatment of patients diagnosed with partial onset seizures. This article can help researchers and analysts to build upon this knowledge and add further methods of analysis in the future.

In the last few decades, many new antiepileptic drugs came out to medicine world, and their use was expanded over a wide range of cases. Analysts from all over the world developed many different separation methods for the determination of these drugs in a quantitative way either in pharmaceutical dosage forms or in biological fluids. In this review article, a summation of previously published separation methods including high-performance thin-layer chromatography, high-performance liquid chromatography, gas chromatography, and electrophoresis used for the determination of eslicarbazepine acetate, levetiracetam, lacosamide, oxcarbazepine, pregabalin, and retigabine are presented. These six drugs are the most commonly used drugs for the treatment of patients diagnosed with partial onset seizures. This article can help researchers and analysts to build upon this knowledge and add further methods of analysis in the future.

This study examines the potential of application of capillary zone electrophoresis (CZE) coupled to laser-induced fluorescence (LIF) detection involving derivatization with fluorescamine for the separation and determination of α-aminocephalosporins in surface water samples. Via their α-amino group, the non-fluorescent cefadroxil and cefalexin are capable of forming a highly fluorescent derivative via their reaction with fluorescamine. This reaction permits the selective and sensitive detection of aliphatic primary amines when combined with CE/LIF, which was achieved with a low-noise diode laser emitting at a wavelength of 375 nm (Pcw = 5.6 mW) in combination with a fiber optic-coupled detection cell. Different types of solid phase extraction cartridges were investigated to select the optimum solid phase providing maximum recovery for the studied antibiotics, which were extracted from spiked Lahn river water samples. Highest recovery (cefalexin 109.4 ± 3.9 % and cefadroxil 92.6 ± 4.0 %) was reached with a polymer-based solid phase (Oasis HLB cartridge), with which a tenfold off-line enrichment was obtained. On-line enrichment was achieved by sweeping and large volume sample stacking (LVSS). The high complex formation constant between the formed derivative and 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) and the low electric conductivity of the extract after the off-line enrichment constitute an ideal basis for additional analyte enrichment by sweeping and LVSS. The enrichment efficiency obtainable with this on-line enrichment step (after having filled the complete capillary with the sample solution) in comparison to field-amplified sample stacking (FASS) reaches approximately an additional 25-fold improvement. With the developed method, combining off-line and on-line enrichment with optimized fluorescence detection, detection limits as low as 4.9 and 7.5 ng L−1 are obtained for cefalexin and cefadroxil, respectively, with a starting sample volume as low as 50 mL. The high repeatability and accuracy of the proposed strategy permits its application to the analysis of α-aminocephalosporins in surface water samples. Its applicability can be extended to other environmental compartments and other types of primary amino group containing compounds. In addition, it provides equivalent sensitivity to other methods using more expensive equipment like HPLC–MS/MS.

In this work, we extend our investigations regarding the separation of urinary nucleosides by MEKC with the ionic liquid type surfactant 1-tetradecyl-3-methylimidazolium bromide (C14MImBr). We study the impact of adding alkyl- and arylboronic acids (in the presence of C14MImBr micelles) to the separation of these highly hydrophilic metabolites and investigate the mechanism of interaction between the negatively charged nucleosides (the negative charge is acquired either due to deprotonation of the amidic group and/or complexation with boronate) and the positively charged pseudostationary phase. This interaction is not only due to electrostatic (Coulombic) forces, but also due to hydrophobic interaction of the alkyl or aryl group of the boronate that forms a complex with the cisdiol group of the nucleoside. In this case, alkylboronates can act as a cosurfactant that increases the partitioning coefficient of the analytes into the micelles. In the presence of an alkylboronate in the BGE (employing only 20 mmol/L C14MImBr), the retention factors of the studied analytes are increased considerably when compared to a BGE without this additive. It is shown that the concept of one-site hydrophobically assisted ion exchange can be applied to describe the observed retention behavior. The high selectivity of boronates toward cis-diol-containing compounds can be used to adjust selectively the migration behavior of members of this compound class. By adding alkylboronic acid to the BGE, the separation selectivity is fine-tuned so that interferences from matrix components can be avoided in real sample analysis.

The combination of dynamic pH junction, sweeping (using borate complexation), and large volume sample stacking (LVSS) is investigated as three consecutive steps for on-line focusing in the sensitive quantitation of urinary nucleosides by CE-UVD. A low conductivity aqueous sample matrix free from borate and a high conductivity BGE (containing borate, pH 9.25) are needed to fulfill the required conditions for dynamic pH junction, LVSS, and sweeping. Parameters affecting the separation and the enrichment efficiency are studied such as buffer concentration, separation voltage, capillary temperature, sample composition, and sample injection volume. Prerequisite for the developed strategy is the extraction of the nucleosides from urine using a phenylboronate affinity gel, which is described to be a unique means for the selective enrichment of cis-diol metabolites under alkaline conditions. The impact of ionic constituents remaining in the eluate after extraction on focusing efficiency and resolution is investigated. The developed method is applied to the analysis of blank and spiked urine samples. Fundamental aspects underlying the proposed enrichment procedure are discussed. A detection limit as low as 10 ng mL−1 is achieved. To the best of our knowledge, this LOD represents the lowest LOD reported so far for the analysis of nucleosides using CE with UV detection and provides a comparable sensitivity to CE/MS. Because of the high sensitivity, the proposed method shows a great potential for the analysis of nucleosides in human urine and other types of biological fluids.

A comprehensive review with 276 references for the analysis of members of an important class of drugs, cephalosporin antibiotics, is presented. The review covers most of the methods described for the analysis of these drugs in pure forms, in different pharmaceutical dosage forms and in biological fluids.

A comprehensive review with 276 references for the analysis of members of an important class of drugs, cephalosporin antibiotics, is presented. The review covers most of the methods described for the analysis of these drugs in pure forms, in different pharmaceutical dosage forms and in biological fluids.