The selection of suitable columns for a reversed-phase liquid chromatographic separation of beta-lactam antibiotics and related substances via chromatographic column parameters.

The selection of RP-LC columns suitable for a particular analysis in official compendia is difficult as only a general description of the stationary phase in the description of a LC method is given. General methods to characterize RP-LC columns often assume that each of the column parameters is equally important. This can cause the user to select columns inappropriate for particular analyses. This paper focuses on the relationship between the critical peak pairs and the column parameters (H, S, A, B, and C) in the Snyder/Dolan column characterization methodology to find the key parameters influencing real separations. Some varieties of ß-lactam antibiotics and their related compounds were used as test compounds. We found column parameter A to be the most important factor affecting their separation. Parameters B and C also played an important role in some separation processes. This indicated that the hydrogen bonding of column and solute can directly affect the separation of ß-lactam antibiotics. Choosing columns for which column parameter A is near 0.1 can facilitate the ideal separations of impurities from ß-lactam antibiotics. The most suitable column for any common pharmaceutical analysis could be selected easily if the key column parameters would be given in the description of the chromatographic method. For these reasons, key column parameters should be listed in the monographs of official compendia.

Electrochemical determination of cefotaxime based on a three-dimensional molecularly imprinted film sensor.

A novel electrochemical sensor is presented for the determination of cefotaxime (CEF), which is constructed by molecularly imprinted polymer (MIP), gold networks@IL (IL, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]) (GNWs@IL), porous platinum nanoparticles (PPNPs) and carboxyl graphene (COOH-r-GO). The GNWs@IL is prepared by directly reducing HAuCl4 with sodium citrate in [BMIM][BF4] aqueous solution. The PPNPs are well embedded in GNWs@IL due to the adhesion of IL to form GNWs@IL-PPNPs suspension, which is coated on a COOH-r-GO modified glassy carbon electrode to construct a porous three-dimensional networks modified electrode. Then, MIP is prepared by cyclic voltammetry at the modified electrode, using CEF as template and o-phenylenediamine as monomer. The factors concerning this assay strategy are carefully investigated. Under the optimal conditions, the electrochemical sensor offers an excellent response for CEF, the linear response range is 3.9 × 10(-9) ~ 8.9 × 10(-6) mol L(-1) and the detection limit is 1.0 × 10(-10) mol L(-1). The electrochemical sensor has been applied to the determination of CEF in real samples with satisfactory results.

Separation and determination of cefotaxime enantiomers in injections by capillary zone electrophoresis.

Cefotaxime enantiomers have specific effects on Gram-negative bacteria. For quality control of cefotaxime it was necessary to establish a method for enantioseparation by capillary zone electrophoresis (CZE) using cyclodextrin (CD) as a chiral selector. The effects of various parameters on enantioseparation were studied. A fused silica capillary (40 cm effective length x 75 microm ID) was used. The cefotaxime enantiomers were separated on the baseline under conditions of 0.5 mmol/L CM-beta-CD, 75 mmol/L NaH2PO4 buffer at pH 7.0 using UV detection at 280 nm. Applied voltage and capillary temperature were 20 kV and 25 degrees C, respectively. Under these conditions for enantioseparation, linear calibration curves were obtained in the range 2 approximately 160 microg/mL. The limit of detection for both isomers was less than 0.5 microg/mL. The method was used for analysis of pharmaceutical preparations (dosage forms) of cefotaxime from various factories. A simple and specific CZE method was successfully demonstrated for the separation of cefotaxime enantiomers. The enantioseparation method should be established and this method should be used to control the quality of cefotaxime.

Valoración in vitro de discos para antibiogramas de producción nacional / In vitro assessment of discs for antibiograms of national production

Se realizó la valoración in vitro de discos de antibióticos para antibiogramas producidos por primera vez en nuestro país. Estos correspondieron a ceftriaxoma, cefotaxima, cefazolina, cefuroxima, ceftazidima, ciprofloxacina, vancomicina y oxacillín. Dicha valoración comprendió la actividad in vitro de los discos, así como la determinación del grado de estabilidad de éstos. Fueron utilizadas 911 cepas bacterianas, incluidas bacterias gammnegativas y grampositivas, aisladas en pacientes del hospital. Se determinó que la ciprofloxacina fue el antibiótico más efectivo de todos. De forma global los antibióticos probados tuvieron muy buena actividad inhibitoria frente a bacterias grampositivas y en menor grado frente a gramnegativas. Se compararon los resultados obtenidos usando discos de producción nacional de 4 antibióticos y sus similares de producción extranjera. La ceftriaxona y la ceftaxioma nacionales alcanzaron mejores resultados, en oxacillín los resultados fueron idénticos en ambos y sólo en ciprofloxacina los discos nacionales tuvieron resultados ligeramente inferiores. Se comprobó que los discos probados mantuvieron su potencia a lo largo del estudio y no sufrieron alteraciones en su estado físico