Development and validation of a fully automated LC method for the determination of cloxacillin in human plasma using anion exchange restricted access material for sample clean-up

Subcritical water oxidation of 6-aminopenicillanic acid and cloxacillin using H2O2, K2S2O8, and O2

This study was undertaken to investigate the degradation of 6-aminopenicillanic acid (6-APA) and cloxacillin in aqueous solution by the combined effect of subcritical water and the oxidising agents O₂, H₂O₂, and K₂S₂O₈. Nano ZnO was used as a solid catalyst. Response surface methodology was used to determine the optimum experimental parameters (temperature, treatment time, and concentration of oxidising agent). For 6-APA, the maximum organic carbon (TOC) removal rates of 83.54%, 81.11% and 42.42% were obtained using H₂O₂, K₂S₂O₈, and O₂, respectively. For cloxacillin, the maximum TOC removal rates of 67.69%, 76.02% and 14.45% were obtained using H₂O₂, K₂S₂O₈, and O₂, respectively. Additionally, the impact of nano and commercial ZnO on TOC removal rates was determined. Secondary ions produced during the degradation process-such as nitrite, nitrate, sulphate and chloride-were determined using ion chromatography.

Circular dichroism spectroscopy: An efficient approach for the quantitation of ampicillin in presence of cloxacillin

Ampicillin exhibited a negative and a positive cotton effects on the circular dichroism (CD) spectra in the wavelength range of 200-280nm. Cloxacillin showed a positive cotton band peaking at 228nm. Three sensitive, precise and accurate CD spectroscopic methods have been developed for the determination of ampicillin and cloxacillin. Method A was used for the determination of ampicillin in presence of cloxacillin by measuring ellipticity at 206nm. Method B and C were employed to determine ampicillin and cloxacillin based on evaluation of ellipticity at 233nm and 228nm, respectively. Methods A, B and C showed linearity in the concentration range of 10-40μgmL(-1), 5-40μgmL(-1) ampicillin and 10-80μgmL(-1) cloxacillin, respectively. The method A was successfully applied to the determination of ampicillin in commercial dosage forms containing equivalent amount of cloxacillin.

Flow-injection chemiluminescence determination of cloxacillin in water samples and pharmaceutical preparation by using CuO nanosheets-enhanced luminol-hydrogen peroxide system

In this paper, a rapid and sensitive flow-injection chemiluminescence (flow-CL) system was developed for the determination of cloxacillin sodium in environmental water samples and pharmaceutical preparations. The method was based on the enhancement effect of cloxacillin sodium on the CL reaction of luminal-H₂O₂-CuO nanosheets (NSs) in alkaline medium. The CuO nanosheets were synthesized using a green sonochemical method. The physical properties of the synthesized CuO nanosheets were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The influences of various experimental factors such as H₂O₂, NaOH, luminol and CuO nanosheets concentrations were investigated. Under the optimum conditions, the enhanced CL intensity was linearly related to the concentration of cloxacillin sodium in the range of the 0.05-30.00 mg L(-1) with a correlation coefficient of 0.995. The corresponding detection limit (3σ) was calculated to be 0.026 mg L(-1). The relative standard deviation (RSD) of the developed method was 2.21% with 11 repeated measurements of 4.00 mg L(-1) cloxacillin sodium. Also, a total analysis time per sample was 30 s which confirmed the rapidity of the proposed method. The analytical applicability of the proposed CL system was assessed by determining cloxacillin sodium in spiked environmental water samples and pharmaceutical preparation. Furthermore, the possible mechanism of CL reaction was discussed.

Restricted-access media supports for direct high-throughput analysis of biological fluid samples: review of recent applications

This review presents an update on the use of restricted-access materials (RAMs) for direct injection of biological samples. The fundamental improvements in the preparation of tailored RAMs and the diversity of applications with these phases are presented. Insights into diminishing the matrix effect by the use of RAM supports in methods by LC–MS and into the low number of methods for enantiomeric separations by direct injections of biological samples are addressed. The diversity of systems that incorporate RAMs for selective sample clean-up or fractionation in proteome and peptidome analysis is also covered.

Harmonization of strategies for the validation of quantitative analytical procedures: a SFSTP proposal part IV. Examples of application

A harmonized approach for the validation of analytical methods based on accuracy profile was introduced by a SFSTP commission on the validation of analytical procedure. This fourth and last document aims at illustrating this methodology and the statistics used. Therefore the validation of real case methods are proposed such as methods for the quality control of drugs, for the quantitation of impurities in drug substances, for bioanalysis or for the determination of nutriments. Furthermore, different types of analytical methods are used in order to demonstrate the applicability of the proposed approach to a wide range of methods such as liquid chromatography (LC-UV, LC-MS), spectrophotometry or ELISA.

Development of a validated HPLC method for the determination of four penicillin antibiotics in pharmaceuticals and human biological fluids

A quantitative method for the determination of four penicillin antibiotics, amoxicillin (AMO), oxacillin (OXA), cloxacillin (CLO), and dicloxacillin (DICLO), has been developed. Separation was achieved on an Inertsil ODS-3 (250 x 4 mm, 5 microm) column after selective extraction of penicillin drugs from biological matrices by means of SPE. Gradient elution with a mobile phase consisting of 0.1% TFA (pH 1) and ACN, and PDA detection with monitoring at 240 nm was applied. Salicylic acid (5 ng/microL) was used as the internal standard. RP-8 Adsorbex Merck cartridges provided high absolute recoveries (98-101%). The developed method was fully validated in terms of selectivity, linearity, accuracy, precision, stability, and sensitivity. Repeatability (n = 8) and between-day precision (n = 8) revealed RSD <10%. Recoveries from biological samples ranged from 91 to 103%. The detection limits were estimated as 3.3 ng for AMO, OXA, and CLO, and 6.6 for DICLO in blood plasma. LOD in whole blood and urine was 6.6 ng. Injection volume was 20 microL. The method was applied to commercially available AMO containing pharmaceuticals and spiked biological matrices. The method was also applied to biological samples after AMO oral administration, where the drug was successfully identified and quantified.

Recent developments in extraction procedures relevant to analytical toxicology

Sample preparation is an important step in the development of an analytical method but is often regarded as time-consuming, laborious work. Optimum sample preparation leads to enhanced selectivity and sensitivity, however, and reduces amounts of interfering matrix compounds, resulting in less signal suppression or enhancement. Recent developments in extraction techniques that could be of interest in clinical and forensic toxicology, for example liquid-liquid, solid-phase, and headspace extraction, are summarized in this review. The advantages and disadvantages of several extraction techniques are discussed, to enable the reader to choose an appropriate method of extraction for his or her application. Attention is paid to current trends in analytical toxicology, for example miniaturization, high throughput, and automation.

Sensitive determination of aspirin and its metabolites in plasma by LC-UV using on-line solid-phase extraction with methylcellulose-immobilized anion-exchange restricted access media

We describe a sensitive determination of aspirin (ASA) and its three metabolites (salicylic acid [SA], 2,3-dihydroxybenzoic acid [2,3-DHBA], and 2,5-dihydroxybenzoic acid [gentisic acid (GA)]) in rat plasma. Analysis was carried out by on-line solid-phase extraction (SPE) using a methylcellulose-immobilized-strong anion-exchanger (MC-SAX), followed by liquid chromatography (LC) coupled with UV detection. The lower limits of quantitation for ASA and SA were 60 ng/mL in 100 microL of plasma, respectively. This method was validated with respect to intra- and inter-day precision, accuracy, and linearity up to concentrations of 20,000 ng/mL for ASA, SA, 2,3-DHBA and gentisic acid, respectively. The method was successfully applied to an analysis of the pharmacokinetics of ASA and SA in rats.

Chromatographic analysis of penicillins in pharmaceutical formulations and biological fluids

Natural penicillin (benzylpenicillin) is the oldest antibiotic observed by Alexander Fleming in 1928. To broaden its spectrum of activity, natural penicillin was modified, giving rise to a group of antibiotics under the name 'penicillins'. Although an increasing number of bacteria appear to be resistant to them, penicillins are used to treat a variety of bacterial infections including Gram-positive, Gram-negative aerobic and anaerobic bacteria. Consequently, they are widely used in human and veterinary medicine to prevent and treat diseases. This review covers the analytical methodologies, mainly chromatographic, employed to the penicillins determination in pharmaceutical formulations, biological fluids and in production-scale fermentations reported in the literature. Results of published assays are comparatively presented focusing on sample preparation regarding isolation and purification, chromatographic conditions and method validation. Information on chemical structure, spectrum of activity and action mechanism of common penicillins has also been given.

HPLC determination of ciprofloxacin, cloxacillin, and ibuprofen drugs in human urine samples

This paper reports, for the first time, a liquid chromatographic method for the simultaneous determination of three frequently co-administered active principles, two antibiotics, ciprofloxacin (CIPRO) and cloxacillin (CLOXA) belonging to the fluoroquinolones and beta-lactam families, respectively, and ibuprofen (IBU), a non-steroidal anti-inflammatory drug. The chromatographic separation was performed on a C-18 analytical column, using isocratic elution with methanol-acetonitrile-pH 3 formate buffer (CT = 0.1 M) (15:12:73, v/v/v) for 3 min and, after that, a linear gradient with methanol-acetonitrile (88:12, v/v) for 8 min. Several absorption spectra were obtained for each peak using a DAD detector. Chromatograms at the maximum absorption wavelength for each analyte, 220 nm for both IBU and CLOXA, and 280 nm for CIPRO were selected as the most suitable. The proposed chromatographic method requires about 15 min per sample. The presence of a urine background was tested and no interference was found. The method was satisfactorily applied to the determination of CIPRO, CLOXA, and IBU, in fortified urine, and in urine samples from a patient undergoing treatment with these three active principles, among others. Limits of quantification in urine were 1.00, 1.70, and 2.87 microg/mL for CIPRO, CLOXA, and IBU, respectively.

A new approach to evaluate regression models during validation of bioanalytical assays

The quality of bioanalytical data is highly dependent on using an appropriate regression model for calibration curves. Non-weighted linear regression has traditionally been used but is not necessarily the optimal model. Bioanalytical assays generally benefit from using either data transformation and/or weighting since variance normally increases with concentration. A data set with calibrators ranging from 9 to 10000 ng/mL was used to compare a new approach with the traditional approach for selecting an optimal regression model. The new approach used a combination of relative residuals at each calibration level together with precision and accuracy of independent quality control samples over 4 days to select and justify the best regression model. The results showed that log-log transformation without weighting was the simplest model to fit the calibration data and ensure good predictability for this data set.

Development of restricted-access media supports and their application to the direct analysis of biological fluid samples via high-performance liquid chromatography

A quick overview of published methods for analyzing compounds in complex biological samples reveals that the most difficult step is the clean-up or extraction of a required compound from the matrix. The strategy required to analyze exogenous compounds in biological fluids depends greatly upon the nature of the compound and upon the biomatrix. Coupled-column separation using restricted-access media as the first dimension in order to exclude macromolecules and retain micromolecules has been successfully used for a number of biological fluids. This paper presents the history of the development of restricted-access media supports and of their application to the direct injection of biological fluid samples in high-performance liquid chromatography.

On-line pretreatment using methylcellulose-immobilized cation-exchange restricted access media for direct liquid chromatography/mass spectrometric determination of basic drugs in plasma

A novel methylcellulose-immobilized restricted access media column with strong cation-exchange groups on an internal surface (MC-SCX) was evaluated for the direct injection analysis of basic polar drugs in plasma by column-switching liquid chromatography/mass spectrometry (LC/MS). Analytical conditions, including an automated pretreatment step and MS detection, were optimized for a series of basic drugs (doxepin, desipramine, imipramine, nortriptyline, amitriptyline, clomipramine). On-line pretreatment with the MC-SCX column followed by fast gradient analysis using a C18 column resulted in a total analysis cycle time of 7 min for each spiked plasma sample. More than 150 plasma samples spiked with target compounds were measured without compromising MS detection (relative standard deviations less than 11% for all compounds, and regression coefficients greater than 0.99).