Highly sensitive trivalent copper chelate-luminol chemiluminescence system for capillary electrophoresis chiral separation and determination of ofloxacin enantiomers in urine samples

Online preconcentration and chiral separation of ofloxacin in exhaled breath condensate by capillary electrophoresis

Breath analysis is an effective method of monitoring systemic or respiratory ailments. A simple chiral capillary electrophoresis method coupled with an online field-amplified sample injection stacking method is presented for ultratrace quantification of the enantiomers of ofloxacin in exhaled breath condensate (EBC). The study is focused on the use of EBC as an easily available biological sample to monitor ofloxacin's enantiomers levels with good patient compliance. The proposed method was validated in accordance with FDA guidelines over the concentration range of 0.004-1.0 µg mL-1 of racemic ofloxacin. Inter- and intra-day precision and accuracy were within the acceptable limit (below 8.50 %). The method was specific for routine analysis of ofloxacin's enantiomers. A small volume of EBC samples from seven patients under ofloxacin therapy was analyzed using the proposed method in which the concentrations of "R" and "S" enantiomers were between 0.0026 and 0.056 µg mL-1.

Enhanced antibacterial activity of levofloxacin/hydroxypropyl-β-cyclodextrin inclusion complex: In vitro and in vivo evaluation

Levofloxacin is the levo-enantiomer of ofloxacin (a fluoroquinolone class of antibacterial drug). Cyclodextrins (CDs) including hydroxypropyl-β-cyclodextrin (HPβCD) are generally used as a chiral selector for the enantioseparation of some drugs including levofloxacin or as a drug/food nanocarrier for the efficacy improvement of many pharmaceuticals. We hypothesized that the cyclodextrin inclusion is potentially able to further improve the antibacterial activity of levofloxacin. To test this hypothesis, the levofloxacin/HPβCD inclusion complex was prepared by the freeze-drying method and characterized by phase solubility diagram, differential scanning calorimetry (DSC), X-ray diffractometry (XRD), UV-Vis spectrophotometer, and ¹H NMR spectroscopy, confirming the successful HPβCD inclusion of levofloxacin. The in vitro antibacterial effects of HPβCD, levofloxacin, and the levofloxacin/HPβCD inclusion complex against four different bacterial strains in liquid media and on agar plates were determined/compared (an MIC₉₀ of 0.5-1.0 μg/mL for the inclusion complex compared with that of 1.0-2.0 μg/mL for free levofloxacin in liquid). Moreover, the in vivo antibacterial effects of levofloxacin and levofloxacin/HPβCD inclusion complex were tested by using a skin scald model in mice infected with Staphylococcus aureus, and decreased amounts of both bacteria and leukocytes were detected in scalded skin after the inclusion complex treatment. The data revealed that the levofloxacin/HPβCD inclusion complex had an enhanced antibacterial activity compared with free levofloxacin. It implies that cyclodextrins (e.g. HPβCD) may have a beneficial role when using as a chiral selector or as a drug nanocarrier for levofloxacin and that the levofloxacin/HPβCD inclusion complex has the potential of being developed into a pharmaceutical for antibacterial therapies.

Optimization of a Ligand Exchange Chromatography Method for the Enantioselective Separation of Levofloxacin and Its Chiral Impurity

BACKGROUND

Levofloxacin is a third-generation fluoroquinolone that has several advantages over its (R) ofloxacin isomer. It is used to treat different types of infection, including urinary infection and prostatitis.

OBJECTIVE

A new HPLC method for the enantioselective separation of levofloxacin and its chiral impurity was developed and validated to improve the separation of the enantiomers of levofloxacin [impurity(R) and active principle (S)] by increasing the value of the resolution between the eutomer and the distomer.

METHOD

Chromatographic separation was performed on a Prodigy ODS -2, 5 µm 4.6 × 150 mm column, with a gradient of buffer solution and methanol (80:20, v/v). A Box-Behnken design was considered when optimizing the enantioseparation involving the effects of many factors such as the concentration of d-phenylalanine, the pH of the buffer, the percentage of organic modifier in the mobile phase, the flow rate, the temperature of the column, and the type of column.

RESULTS

Chiral separation was achieved with an optimal resolution of 3.8. The method was successfully validated following the International Conference on Harmonization Q2 (R1) guideline, fulfilling the acceptance criteria for selectivity [no interference in the retention time of (S) levofloxacin and (R) levofloxacin], linearity (r ≥0.999 in the range 1.25-3.75 µg/mL for all enantiomers), and precision (RSD <2%). Accuracy was assessed by the application of the analytical method to an analyte of known purity, providing evidence for the usefulness of this monitoring system.

CONCLUSIONS

The method was successfully used for the determination of levofloxacin impurity in raw material and pharmaceutical dosage forms.

HIGHLIGHTS

The following method is accurate and robust to quantify and characterize the presence of levofloxacin impurity in raw material for pharmaceutical compounds.

Determination of levofloxacin by HPLC with fluorescence detection in human breast milk

Aim: A new HPLC method with fluorescence detection has been developed and validated for the determination of levofloxacin, one of the fluoroquinolone class antibiotics, in breast milk. Materials & methods: Chromatographic separation was carried out on a reversed phase C18 column with acetonitrile and 10 mM o-phosphoric acid (25:75, v/v) mobile phase composition. Moxifloxacin was used as internal standard and the peaks were detected by fluorescence detection. Results & conclusion: Calibration graph was found linearly within the range of 2.5-500 ng/ml. Limit of detection and limit of quantification were found to be 0.63 and 2.11 ng/ml, respectively. Mean absolute recovery was 96.18%. The developed method has been successfully applied to the determination of levofloxacin in human breast milk taken from two healthy volunteers.

Kinetics and Mechanism of Oxidation of Carbenicillin by Copper (III) Periodate Complex in Aqueous Alkaline Medium

Kinetics and mechanism of oxidation of carbenicillin by diperiodatocuprate [DPC-III] in aqueous alkaline medium were studied spectrophotometrically at 298 K and an ionic strength of 0.10 mol·dm−3. The reaction between DPC (III) and carbenicillin in the alkaline medium showed (CRBC : DPC-III) 1 : 4 stoichiometry. The reaction products were identified by the CHNS test, FT-IR, and LC-MS spectral reports. The reaction was of pseudo-first order with respect to DPC (III) and fractional order with respect to carbenicillin as well as alkali but retarding effect with respect to periodate. Monoperiodatocuprate (MPC-III) was found to be the main active species in the alkaline medium in the form of [Cu (H2IO6) (H2O)2]. Activation and thermodynamic parameters with respect to uncatalyzed rate constants (ku) and slow step rate constant (k) as well as equilibrium constants were determined. The plausible mechanism consistent with experimental results was proposed and discussed in detail.

Applications of capillary electrophoresis with chemiluminescence detection in clinical, environmental and food analysis. A review

This paper reviews the latest developments and analytical applications of chemiluminescence detection coupled to capillary electrophoresis (CE-CL). Different sections considering the most common CL systems have been included, such as the tris(2,2'-bipyridine)ruthenium(II) system, the luminol and acridinium derivative reactions, the peroxyoxalate CL or direct oxidations. Improvements in instrumental designs, new strategies for improving both resolution and sensitivity, and applications in different fields such as clinical, pharmaceutical, environmental and food analysis have been included. This review covers the literature from 2010 to 2015.