Optimization of separation and migration behavior of cephalosporins in capillary zone electrophoresis

The binding characteristics of sediment-derived dissolved organic matter with ceftazidime: a microstructural and spectroscopic correlation study

This research focused on the characterization of sediment-derived dissolved organic matter (SDOM) extracted from sediment of Yellow River and the binding behaviors of ceftazidime (CAZ) with the presence of SDOM. The morphology, surface composition and structure of SDOM and the complexation between SDOM and CAZ in terms of component features, binding capacity and sequence were studied by multiple approaches. Results showed that SDOM was in situ autochthonous-dominated with a low weight-average molecular weight and aromaticity (the value of S_R was 2.523). The multiple morphological characteristics, high surface oxygen contents (53.49%) and more aliphatic (H/C = 1.91) of SDOM were further confirmed. Studies on SDOM-CAZ interaction suggested that the functional groups and chemical compositions of SDOM were susceptible to CAZ. In more detail, the aromatic protons and aliphatic protons of CAZ impacted significantly, and the binding between CAZ and SDOM might relate to noncovalent. The protein-like fractions were considered to be the primary participant with 49% fractions lost and the aromatics and amides as mainly active site interaction with CAZ. These findings have significant implications on the environmental fate of cephalosporin antibiotics and that of sediment-derived DOM.

Cephalosporin antibiotics in the aquatic environment: A critical review of occurrence, fate, ecotoxicity and removal technologies

Due to their widespread occurrence in the aquatic environment, human and veterinary cephalosporin antibiotics have been studied as water pollutants. In order to characterize environmental risks of this compound class, this review evaluates relevant data about physicochemical properties, occurrence, ecotoxicity and degradation of cephalosporins. Although application of cephalosporins is rather low compared to other antibiotics and their environmental life-time is believed to be short (i.e. days), the available data is insufficient to draw conclusions on their environmental relevance. Few studies concerning the fate of cephalosporins in soil are available, while hydrolysis and photo-degradation are suggested as the main attenuation processes in the aquatic environment. Cephalosporins have been detected in different aqueous matrices in concentrations ranging from 0.30 ng L^-1 to 0.03 mg L^-1, with sewage and wastewater being the main matrices with positive findings. For wastewater treatment purposes, several technologies have been tested for the abatement of cephalosporins, including photolysis and adsorption. In most cases, the technology employed led to complete or significant removal (>95%) of parental drugs but few authors reported on cephalosporins' metabolites and transformation products. Furthermore, the present ecotoxicological data are insufficient for comprehensive ecological risk quotient calculations. Considering the total of 53 cephalosporins, effective values (EC, LC, NOAEC, NOAEL, etc.) are only available for around 30% of parental drugs and are very scarce for cyanobacteria, which is considered to be the most sensitive group of organisms to antibiotics. Furthermore, it has been demonstrated that cephalosporins' transformation products can be more toxic and more persistent than the parental drugs. Few investigations considering this possibility are available. Consequently, more effort on ecotoxicological data generation and verification of biological inactivation of cephalosporins-related products is needed. Likewise, the lack of natural depletion rates and knowledge gaps on mixture effects for cephalosporins' degradation and toxicity have to be overcome.

Determination of acid dissociation constants (pKa) of cephalosporin antibiotics: Computational and experimental approaches

Cefapirin (CEPA) and ceftiofur (CEF) are two examples of widely used veterinarian cephalosporins presenting multiple ionization centers. However, the acid dissociation constants (pK_a) of CEF are missing and experimental data about CEPA are rare. The same is true for many cephalosporins, where available data are either incomplete or even wrong. Environmentally relevant biotic and abiotic processes depend primordially on the antibiotic pH-dependent speciation. Consequently, this physicochemical parameter should be reliable, including the correct ionization center identification. In this direction, two experimental techniques, potentiometry and spectrophotometry, along with two well-known pK_a predictors, Marvin and ACD/Percepta, were used to study the macro dissociation constants of CEPA and CEF. Additionally, the experimental dissociation constants of 14 cephalosporins available in the literature were revised, compiled and compared with data obtained in silico. Only one value was determined experimentally for CEF (2.68 ± 0.05), which was associated to the carboxylic acid group deprotonation. For CEPA two values were obtained experimentally: 2.74 ± 0.01 for the carboxylic acid deprotonation and 5.13 ± 0.01 for the pyridinium ring deprotonation. In general, experimentally obtained values agree with the in silico predicted data (ACD/Percepta RMSE: 0.552 and Marvin RMSE: 0.706, n = 88). However, for cephalosporins having imine and aminothiazole groups structurally close, Marvin presented problems in pK_a predictions. For the biological and environmental fate and effect discussion, it is important to recognize that CEPA and CEF, as well as many other cephalosporins, are present as anionic species in the biologic and environmentally relevant pH values of 6-7.5.

Electrophoretic stacking for sensitive determination of antibiotic ceftazidime in human blood and microdialysates from diabetic foot

An electrophoretic stacking method has been developed for monitoring the therapeutic level of the antibiotic ceftazidime in blood plasma and microdialysates taken from peripheral soft tissues of the lower limbs of patients with diabetic foot syndrome. The biological samples are treated by addition of acetonitrile in an amount of 75% v/v and injected into a capillary in a large volume; after turning on the separation voltage, the residual acetonitrile is forced out of the capillary by the application of hydrodynamic pressure. The clinical samples were separated in an optimised background electrolyte composed of 50 mM chloroacetic acid +20% v/v methanol +0.5% v/v INST coating solution. The attained LOD for ceftazidime equalled 0.42 μg mL^-1 (0.8 μM) and the migration time equalled 3.75 min when using a 25 μm capillary with minimum length of 31.5 cm. The separation was controlled by a maximum voltage of +30 kV and the movement of the analyte was accelerated by a pressure of 50 mbar. The RSD values for intra-day repeatability of the migration time and peak area are 0.14% and 3.8%, respectively; the inter-day values equalled 0.25% for the migration time and 7.3% for peak area, respectively. Pharmacological studies revealed that ceftazidime passes from the blood circulation to the peripheral tissues of the lower limbs with an efficiency of 20%. The introduction of CE control of ceftazidime level in diabetic foot represents a very important improvement in achieving the targeted therapeutic effect.

Study of the Electrophoretic Behavior of Cephalosporins by Capillary Zone Electrophoresis

PURPOSE

The aim of the study was the characterization of the electrophoretic behavior of cephalosporins from different generation having different structural characteristics in order to develop a rapid, simple and efficient capillary electrophoretic method for their identification and simultaneous separation from complex mixtures.

METHODS

Ten cephalosporin derivatives (cefaclor, cefadroxil, cefalexin, cefazolin, cefoxitin, cefuroxime, cefoperazone, cefotaxime, ceftazidime, ceftriaxone) were analyzed by capillary zone electrophoresis using different background electrolyte solutions at different pH values. Electrophoretic mobilities of the analytes were calculated, the influence of the electrophoretic parameteres on the separation was established and the analytical conditions were optimized.

RESULTS

Taking into consideration their structural and chemical properties cephalosporins can be detected over a pH range between 6 and 10. The best results were obtained using a buffer solution containing 25 mM disodium hydrogenophosphate - 25 mM sodium dihydrogenophosphate, at a pH - 7.00, + 25 kV voltage at a temperature of 25 °C, UV detection at 210 nm. Using the optimized analytical conditions we achieved the simultaneous baseline separation for seven cephalosporins in less then 10 minutes.

CONCLUSION

Using the described optimized electrophoretic procedures, capillary electrophoresis can be used for the identification and determination of cephalosporins in formulated pharmaceutical products and for their separation from complex mixtures.

Improving the sensitivity of the determination of ceftiofur by capillary electrophoresis in environmental water samples: In-line solid phase extraction and sample stacking techniques

This paper describes two different approaches for increasing the sensitivity for the analysis of ceftiofur by capillary electrophoresis (CE). Two different techniques based on the introduction of an enlarged volume of sample, namely large volume sample stacking (LVSS) and in-line solid phase extraction (SPE) were studied and compared. LVSS allowed the on-column electrophoretic preconcentration of ceftiofur without modification of the separation capillary. In-line SPE-CE was developed by using a home-made microcartridge that was filled with a reversed-phase sorbent (C(18)). The microcartridge was coupled in-line near the inlet of the separation capillary. LVSS and in-line SPE-CE allowed automated operation and improved sensitivity for the analysis of ceftiofur with respect to conventional CE. When environmental water samples were analyzed, an additional pretreatment step based on off-line SPE was necessary in both cases to further decrease the detection limits. In terms of sensitivity for the determination of ceftiofur in river water samples, the combination of off-line SPE with in-line SPE-CE was found the most sensitive with a detection limit of 10 ng L(-1), whereas the method based on the use of off-line SPE with LVSS presented a detection limit of 100 ng L(-1).

Determination of cefuroxime axetil in tablets and biological fluids using liquid chromatography and flow injection analysis

Cefuroxime axetil is the pro-drug of cephalosporin cefuroxime that is used in the treatment of common community-acquired infections. A simple and precise liquid chromatographic method for the determination of cefuroxime axetil in pharmaceutical tablets, human serum and urine has been developed and validated. Cefuroxime axetil and indapamide (internal standard) were separated by a reversed phase column (Supelco Hypersil 5 microm, 150 mm x 4.6 mm i.d., C18) using a mobile phase consisting of KH2PO4 (0.1 M) and acetonitrile (70:30 v/v) (at pH 4.0). The mobile phase was pumped at 1.0 mL min(-1) flow rate and cefuroxime axetil was detected by ultraviolet detection at 281 nm within an average analysis time of 11 min. Flow injection analysis was performed for pharmaceutical tablet analysis using a carrier stream of methanol:water (10:90v/v) with a flow rate of 1.0 mL min(-1). The LOD and LOQ concentrations of the HPLC method were 1.35 x 10(-7) and 4.08 x 10(-7)M for the HPLC analysis and 1.31 x 10(-7) and 4.00 x 10(-7)M for FIA. The results of the analysis of the tablet formulation obtained by using these methods were statistically comparable with each other and with an additional spectrophotometric method. There was no significant difference between all these methods.

Development of an analytical method for the determination of betaines in higher plants by capillary electrophoresis at low pH

In recent years the role of betaines in higher plants has been extensively investigated in relation to environmental stress response. This paper reports the establishment of a simple, rapid and reliable method for the determination of betaines using capillary electrophoresis (CE) at low pH. Betaines were first converted to their phenacyl esters and the crude reaction mixture was then applied directly to CE without any pre-treatment. Employing an electrolyte running solution at pH 3 gave a well-resolved electropherogram for the esters of glycine betaine (1), trigonelline, proline betaine, gamma-butyro betaine, and carnitine. The content of 1 and its variation in plant samples collected from high-salinity areas in north China and west Australia are presented.

Analysis of antibiotics by capillary electrophoresis

This article reviews recent developments in the characterization of antibiotics. Many capillary electrophoretic techniques have been utilized in their analyses, addressing various aspects of quantifying, profiling and monitoring. Sensitive electrochemical and laser-induced fluorescence detection systems have been utilized, demonstrating trace level determinations in clinical settings and in environmental samples. Different sample introduction methods have been explored, enhancing detection sensitivity, or reducing or eliminating sample manipulation prior to injection.

Measurement of free choline in plant leaves by capillary electrophoresis

A low pH capillary electrophoresis (CE) was used for the measurement of free choline in plant leaves. Choline in the leaf extract was first converted to the benzoyl ester and put into CE. A well-resolved peak in the electropherogram was easily obtained. Involvement of enzymes in a two-step oxidation of choline to glycine betaine was evaluated in different plant species with the same method developed for glycine betaine and betaine aldehyde.