Determination of sulfur-containing antibiotics using high-performance liquid chromatography with integrated pulsed amperometric detection

Analysis of cephalosporin antibiotics

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.

Nanostructured electrode based on multi-wall carbon nanotubes/Pt microparticles nanocomposite for electrochemical determination of thiols in rat striatum by high performance liquid chromatography separation

In this paper, multi-wall carbon nanotubes (MWNTs)/Pt microparticles nanocomposite was prepared by electrodepositing Pt microparticles onto the MWNTs matrix. The surface of glassy carbon electrode was modified with this kind of nanocomposite for measurement of thiols, such as L-cysteine (L-Cys) and glutathione (GSH). Compared with the MWNTs or Pt microparticles modified electrode, the nanocomposite modified electrode exhibited high sensitivity and good stability for detection of thiols. According to the results of experiments, the peak currents of L-Cys and GSH are linear with their concentrations and the detection limits (S/N=3) are 2.9 x 10(-8) mol/L and 4.5 x 10(-8) mol/L, respectively. Coupled with microdialysis, the method has been successfully applied to the determination of these two thiols in rat striatal microdialysates.

A pulsed potential waveform displaying enhanced detection capabilities towards sulfur-containing compounds at a gold working electrode

Pulsed electrochemical detection of sulfur-containing compounds was successfully investigated by applying a four-step potential waveform at a gold working electrode. This potential waveform called APAD, which stands for activated pulsed amperometric detection, is composed of an activation potential step added to a conventional three-step potential waveform. A key advantage of the APAD at the Au electrode is the ability to enhance sensitivity through the use of a short potential pulse (E(ACT) = +750 mV versus Ag/AgCl and tACT approximately 90 ms) during which the formation of redox active species (presumably OH*) are able to efficiently oxidize organosulfur compounds. The APAD waveform parameters were optimized to maximize the signal-to-noise ratio (S/N) and successfully applied for the sensitive detection of lipoic acid, biotin, iminobiotin, methionine, cystine, cysteine, homocysteine, homocystine, N-acetylcysteine and glutathione, following their separations by high-performance anion-exchange chromatography (HPAEC) using alkaline mobile phases. The detection limits (S/N = 3, 10 microL injected) ranged from 0.3 for cysteine (400 pg) to 0.02 micromol/L for biotin (50 pg) and methionine (30 pg). The response of sulfur-, amine- and alcohol-based compounds was compared by using four selected pulsed potential waveforms. It was found that the APAD exhibits excellent sensitivity for thiocompounds outperforming all other pulsed potential waveforms. Ratios of the peak areas for APAD and the six-step potential integrated waveform increased from 3.2 +/- 0.4 to 13.5 +/- 0.6 for lipoic acid and biotin, respectively.

Determination of thio-based additives for biopharmaceuticals by pulsed electrochemical detection following HPLC

Pulsed electrochemical detection (PED) following liquid chromatographic separation has been applied to the direct (i.e., without derivatization) determination of two major sulfur-containing compounds used as pharmaceutical additives, isopropyl-thio-beta-D-galactopyranoside (IPTG) and monothioglycerol (MTG). Limits of detection of IPTG and MTG were found to be 1 ppb (0.2 pmol, 50 microL) and 0.2 ppb (0.1 pmol, 50 microL), respectively, using optimized potential-time waveforms applied to a Au electrode. In addition to high sensitivity as compared to optical detection, the simultaneous detection of free thiols and disulfides can be used to study the kinetics of these conversions, as is shown for MTG. A practical application of HPLC-PED is demonstrated in determining MTG in a pharmaceutical formulation. The high selectivity of PED for thiocompounds reduces sample preparation and produces simpler chromatograms in a variety of matrices.

Lincomycin, cultivation of producing strains and biosynthesis

Lincomycin and its derivatives are antibiotics exhibiting biological activity against Gram-positive bacteria. The semi-synthetic chlorinated lincomycin derivative is used in clinical practice. The chemical structure of lincosamide antibiotics, cultivation of producing strains and analytical procedures used for separation and isolation of these compounds are described in this review. Biosynthesis of lincomycin and related compounds and its genetic control are briefly discussed.