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.

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.

Sweeping is an important online focusing method in capillary zone electrophoresis and electrokinetic chromatography, which is employed in numerous methods for analyte enrichment and improvement of detection and quantitation limits. This review intends to summarize the present state of developments in the understanding of sweeping processes with special emphasis on the modeling of moving and stationary boundaries with assumed moving and/or stationary accelerating or decelerating planes. Starting from the description of sweeping for a neutral analyte under homogeneous field conditions, it is shown that the methodology of modelling zone focusing processes with moving and/or stationary accelerating or decelerating planes allows extending the description to charged analytes, inhomogeneous field conditions, retention factor gradient effect conditions, complex formation ligand as sweeping carrier and dynamic pH junction conditions. The present article introduces a generalized theoretical basis that allows a better understanding of the various factors influencing sweeping processes. The discussion is completed with a section on limitations of the presented approach.

A novel, simple and sensitive electrochemical method for the determination of ledipasvir (LED), the newly FDA approved Hepatitis C antiviral drug was developed and validated using ε-MnO2-modified graphite electrode. Two different MnO2 polymorphs (g- and ε-MnO2 nanoparticles) were synthesized and characterized using X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive X-ray (EDX) and thermogravimetric analysis (TGA). Surface area measurements show that ε-MnO2 NPs have large surface area of 345 m2 /g, which is extremely high if compared to that of g-MnO2 NPs (38 m2 /g). In addition, a comprehensive study of the difference in the electrochemical behavior of LED while using pencil graphite electrode (PGE) modified with either g- or ε-MnO2 NPs is carried out. It was found that surface area and percentage of surface hydroxyls of MnO2 NPs are the key factors governing the sensitivity of the fabricated electrode toward the oxidation of the positively charged LED. Scanning electron microscopy (SEM) was employed to investigate the morphological shape of MnO2 NPs and the surface of the bare and modified electrodes. Moreover, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used for the surface analysis of the modified electrodes. Based on the obtained results, ε-MnO2/PGE was applied as a selective and sensitive electrode for determination of LED. Under the optimized experimental conditions, ε-MnO2/PGE provides a linear response over the concentration range of 0.025e3.60 mmol L1 LED with a low limit of detection, which was found to be 5.10 nmol L1 (4.50 ng mL1 ) for the 1st peak and 9.20 nmol L1 (8.10 ng mL1 ) for the 2nd one. In addition, the oxidation behavior of LED is discussed with a full investigation of the oxidized product using FT-

A novel, simple and sensitive electrochemical method for the determination of ledipasvir (LED), the newly FDA approved Hepatitis C antiviral drug was developed and validated using ε-MnO2-modified graphite electrode. Two different MnO2 polymorphs (g- and ε-MnO2 nanoparticles) were synthesized and characterized using X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive X-ray (EDX) and thermogravimetric analysis (TGA). Surface area measurements show that ε-MnO2 NPs have large surface area of 345 m2 /g, which is extremely high if compared to that of g-MnO2 NPs (38 m2 /g). In addition, a comprehensive study of the difference in the electrochemical behavior of LED while using pencil graphite electrode (PGE) modified with either g- or ε-MnO2 NPs is carried out. It was found that surface area and percentage of surface hydroxyls of MnO2 NPs are the key factors governing the sensitivity of the fabricated electrode toward the oxidation of the positively charged LED. Scanning electron microscopy (SEM) was employed to investigate the morphological shape of MnO2 NPs and the surface of the bare and modified electrodes. Moreover, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used for the surface analysis of the modified electrodes. Based on the obtained results, ε-MnO2/PGE was applied as a selective and sensitive electrode for determination of LED. Under the optimized experimental conditions, ε-MnO2/PGE provides a linear response over the concentration range of 0.025e3.60 mmol L1 LED with a low limit of detection, which was found to be 5.10 nmol L1 (4.50 ng mL1 ) for the 1st peak and 9.20 nmol L1 (8.10 ng mL1 ) for the 2nd one. In addition, the oxidation behavior of LED is discussed with a full investigation of the oxidized product using FT-