Hydrophilic interaction liquid chromatography–tandem mass spectrometry for the determination of levofloxacin in human plasma

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.

Comparison of high-performance liquid chromatography and ultraviolet-visible spectrophotometry to determine the best method to assess Levofloxacin released from mesoporous silica microspheres/nano-hydroxyapatite composite scaffolds

An assessment of Levofloxacin by high-performance liquid chromatography (HPLC) or ultraviolet-visible spectrophotometry (UV-Vis) and its pharmacokinetics in serum or plasma was made in a previous study by the present authors. Levofloxacin-loaded mesoporous silica microspheres/nano-hydroxyapatite (n-HA) composite scaffolds comprise a novel synthetic composite scaffold that may be utilized as a drug-delivery system for clinical usage. However, few studies have been published concerning a comparison of HPLC with UV-Vis, which is the preferred method for determination of Levofloxacin. In the present study, an HPLC method was first established, and subsequently a comparison of HPLC with the UV-Vis method was performed. The standard curve was established, and recovery rate from simulated body fluid was calculated. The linear concentration range for Levofloxacin was 0.05–300 µg/ml. The regression equation for HPLC was y=0.033x+0.010, with R²=0.9991, whereas that for UV-Vis was y=0.065x+0.017, with R²=0.9999. The recovery rates of low, medium and high (5, 25 and 50 µg/ml) concentrations of Levofloxacin determined by HPLC were 96.37±0.50, 110.96±0.23 and 104.79±0.06%, respectively, whereas those for low, medium and high concentrations according to UV-Vis were 96.00±2.00, 99.50±0.00 and 98.67±0.06%, respectively. Taken together, these findings demonstrated that it is not accurate to measure the concentration of drugs loaded on the biodegradable composite composites by UV-Vis. HPLC is the preferred method to evaluate sustained release characteristics of Levofloxacin released from mesoporous silica microspheres/n-HA composite scaffolds. The present study also provides guidance on which methods should be selected for investigating the sustained release properties of drugs in tissue engineering. The accurate determination of drug concentration in the drug delivery system provides guidance for the treatment of infectious diseases.

Meropenem, levofloxacin and linezolid in human plasma of critical care patients: A fast semi-automated micro-extraction by packed sorbent UHPLC-PDA method for their simultaneous determination

An ultra high-performance liquid chromatographic (UHPLC) method with PDA detection was developed and validated for the simultaneous quantification of meropenem, linezolid, and levofloxacin in human plasma and applied in human plasma of critical care patients. A semi-automated microextraction by packed sorbent (MEPS) for sample preparation was used. All parameters in the extraction step (pH, sample volume, sample dilution and number of aspiration - ejection cycles) and in the desorption step (percentage of acetonitrile in the solvent of elution and number of aspirations of elution solvent through the device) were statistically significant when the recovery was used as response. The method showed good linearity with correlation coefficients, r²>0.9991 for the three drugs, as well as high precision (RSD%<10.83% in each case). Accuracy ranged from -7.8% to +6.7%. The limit of quantification of the three drugs was established at 0.01μg/mL for linezolid and levofloxacin and 0.02μg/mL for meropenem. Linezolid, meropenem, levofloxacin and the internal standard were extracted from human plasma with a mean recovery ranged from 92.4% to 97.4%. During validation, the concentration of meropenem, linezolid and levofloxacin was found to be stable after 3 freeze-thaw cycles and for at least 24h after extraction. This method will be subsequently used to quantify the drugs in patients to establish if the dosage regimen given is sufficient to eradicate the infection at the target site.

Analytical Methods for Determining Third and Fourth Generation Fluoroquinolones: A Review

ABSTRACT

Fluoroquinolones of the third and fourth generation posses wide bactericidal activity. Monitoring concentrations of antibacterial agents provides effective therapy and prevents the increase of bacterial resistance to antibiotics. The pharmacodynamic parameters that best describe fluoroquinalone activity are AUC/MIC and Cmax/MIC. Determining the level of this type of drug is essential to reach the effective concentration that inhibits the growth of bacteria. Determining the pharmaceutical formulation confirms the purity of a substance. Many methods have been developed to determine the level of these substances. They involve mainly the following analytical techniques: chromatography, capillary electrophoresis, and spectroscopy. The separation techniques were combined with different measuring devices, such as ultraviolet (UV), fluorescence detector (FLD), diode array detector (DAD), and mass spectrometry (MS). The analytical procedures require proper sample pre-conditioning such as protein precipitation, extraction techniques, filtration, or dilution. This paper reviews the reported analytical methods for the determining representatives of the third and fourth generation of fluoroquinolones. Attention was paid to pre-conditioning of the samples and the applied mobile phase. This report might be helpful in the selection of the proper procedure in determining the abovementioned drugs in different matrices.

GRAPHICAL ABSTRACT

Bioanalysis of antitubercular drugs using liquid chromatography

Tuberculosis is a life threatening disease and second to HIV in terms of deaths due to infectious diseases. Drug resistance development of the first-line drugs is a major concern in the treatment of this disease. There is no comprehensive and critical review in the literature of the bioanalytical methods for the determination of anti-tubercular agents from last two decades. This work offers a detailed account on the liquid chromatographic methods reported in the literature for the estimation of various anti-tubercular drugs. Major emphasis is given to sample preparation process, sensitivity of method, chromatographic separation conditions and detection systems used in their bioanalysis.

Selective Electrochemical Detection of Ciprofloxacin with a Porous Nafion/Multiwalled Carbon Nanotube Composite Film Electrode

This study focuses on the development of electrochemical sensors for the detection of Ciprofloxacin (CFX) in natural waters and wastewater effluents. The sensors are prepared by depositing a layer of multiwalled carbon nanotubes (MWCNTs) dispersed in a porous Nafion film on to a boron-doped diamond (BDD) electrode substrate. The porous-Nafion-MWCNT/BDD electrode enhanced detection of CFX due to selective adsorption, which was accomplished by a combination of electrostatic attraction at -SO3(-) sites in the porous Nafion film and the formation of charge assisted hydrogen bonding between CFX and -COOH MWCNT surface functional groups. By contrast, the bare BDD electrode did not show any activity for CFX oxidation. The sensors were selective for CFX detection in the presence of other antibiotics (i.e., amoxicillin) and other nontarget water constituents (i.e., Cl(-), Ca(2+), humic acid, sodium dodecylbenzenesulfonate, salicylic acid, 4-aminobenzoic acid, and 4-hydroxybenzoic acid). A limit of detection of 5 nM (S/N = 5.04 ± 0.26) in a 0.1 M KH2PO4 supporting electrolyte (pH = 4.5) was obtained using differential pulse voltammetry. The linear dynamic ranges with respect to CFX concentration were 0.005-0.05 μM and 0.05-10 μM, and the sensitivities were 41 ± 5.2 μA μM(-1) and 2.1 ± 0.22 μA μM(-1), respectively. Sensor fouling was observed at high concentrations of some organic compounds such as 1 mM 4-aminobenzoic acid and 4-hydroxybenzoic acid. However, a short cathodic treatment fully restores sensor response. The results indicate that these sensors have application in detecting CFX in natural waters and wastewater effluents.

Average bioequivalence of single 500 mg doses of two oral formulations of levofloxacin: a randomized, open-label, two-period crossover study in healthy adult Brazilian volunteers

Average bioequivalence of two 500 mg levofloxacin formulations available in Brazil, Tavanic(c) (Sanofi-Aventis Farmacêutica Ltda, Brazil, reference product) and Levaquin(c) (Janssen-Cilag Farmacêutica Ltda, Brazil, test product) was evaluated by means of a randomized, open-label, 2-way crossover study performed in 26 healthy Brazilian volunteers under fasting conditions. A single dose of 500 mg levofloxacin tablets was orally administered, and blood samples were collected over a period of 48 hours. Levofloxacin plasmatic concentrations were determined using a validated HPLC method. Pharmacokinetic parameters Cmax, Tmax, Kel, T1/2el, AUC0-t and AUC0-inf were calculated using noncompartmental analysis. Bioequivalence was determined by calculating 90% confidence intervals (90% CI) for the ratio of Cmax, AUC0-t and AUC0-inf values for test and reference products, using logarithmic transformed data. Tolerability was assessed by monitoring vital signs and laboratory analysis results, by subject interviews and by spontaneous report of adverse events. 90% CIs for Cmax, AUC0-t and AUC0-inf were 92.1% - 108.2%, 90.7% - 98.0%, and 94.8% - 100.0%, respectively. Observed adverse events were nausea and headache. It was concluded that Tavanic(c) and Levaquin(c) are bioequivalent, since 90% CIs are within the 80% - 125% interval proposed by regulatory agencies.

Quantile normalization approach for liquid chromatography-mass spectrometry-based metabolomic data from healthy human volunteers

In metabolomic research, it is important to reduce systematic error in experimental conditions. To ensure that metabolomic data from different studies are comparable, it is necessary to remove unwanted systematic factors by data normalization. Several normalization methods are used for metabolomic data, but the best method has not yet been identified. In this study, to reduce variation from non-biological systematic errors, we applied 1-norm, 2-norm, and quantile normalization methods to liquid chromatography-mass spectrometry (LC-MS)-based metabolomic data from human urine samples after oral administration of cyclosporine (high- and low-dose) in healthy volunteers and compared the effectiveness of the three methods. The principal component analysis (PCA) score plot showed more obvious groupings according to the cyclosporine dose after quantile normalization than after the other two methods and prior to normalization. Quantile normalization is a simple and effective method to reduce non-biological systematic variation from human LC-MS-based metabolomic data, revealing the biological variance.

Rapid and sensitive determination of levofloxacin in microsamples of human plasma by high-performance liquid chromatography and its application in a pharmacokinetic study

A rapid, sensitive and simple high-performance liquid chromatographic assay with ultraviolet detection was developed for the quantification of levofloxacin in microsamples (100 μL) of human plasma. The extraction procedure included a protein precipitation technique and a short chromatographic running time (4.5 min). Analyses were carried out on a Symmetry C18 column using a mixture of acetonitrile and 0.01 m potassium dihydrogen aqueous solution (pH 3.4; 14:86 v/v) as mobile phase. The method provided specificity and was linear (r ≥ 0.9992) over the concentration range 0.1-12 µg/mL. The average absolute recovery was 93.59%. The intra- and inter-day coefficients of variation were <6%. Additionally, levofloxacin was stable in all evaluations. The usefulness of this method was demonstrated in a pharmacokinetic study of levofloxacin in healthy adult volunteers. The present method offers two main advantages: (a) the use of microsamples reduces the total volume of blood to be collected from patients; and (b) it provides a good cost-effectiveness ratio. It is concluded that the method is rapid, simple, sensitive, economical and suitable for the determination of levofloxacin in human plasma using a small volume of sample.

Method for simultaneous analysis of nine second-line anti-tuberculosis drugs using UPLC-MS/MS

OBJECTIVES

Therapeutic drug monitoring (TDM) of anti-tuberculosis (TB) drugs is beneficial for patients responding slowly to treatment and those with multidrug-resistant TB. We used ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to develop a rapid method for simultaneously measuring the blood concentrations of nine second-line anti-TB drugs: streptomycin, kanamycin, clarithromycin, cycloserine, moxifloxacin, levofloxacin, para-aminosalicylic acid, prothionamide and linezolid.

METHODS

Serum samples were extracted with acidified methanol and neutralized with NaOH. A Waters Acquity HSS T3 column and gradients of ammonium formate and acetonitrile in 0.1% formic acid were used for UPLC separation. Drug concentrations were determined by multiple reaction monitoring in positive ion mode, and assay performance was evaluated. We applied this method to TDM, analysing random serum samples from 85 patients treated with second-line drugs.

RESULTS

Sample preparation using acidified methanol extraction followed by neutralization yielded good recovery and ionization efficiency, with chromatographic separation achieved within 3 min per sample. Within-run and between-run precisions were 1.7%-7.5% and 1.7%-12.4%, respectively, at concentrations representing low and high levels for the nine drugs. Lower limits of detection and quantification were 0.025-0.5 and 0.25-5.0 μg/mL, respectively. Linearity was acceptable at five concentrations for each drug. No ion suppression was observed at the retention time for most compounds, except for streptomycin, kanamycin and cycloserine, which were eluted close to the void volume of the column. In a limited pilot study, all quantifiable human samples had values within the validated assay ranges.

CONCLUSIONS

The performance of our MS/MS detection technique was generally acceptable. The method provided rapid, sensitive and reproducible quantification of nine second-line anti-TB drugs and should facilitate drug monitoring during treatment.

Hydrophilic interaction chromatography in drug analysis

Hydrophilic interaction chromatography (HILIC) is an increasingly popular alternative to conventional HPLC for drug analysis. It offers increased selectivity and sensitivity, and improved efficiency when quantifying drugs and related compounds in complex matrices such as biological and environmental samples, pharmaceutical formulations, food, and animal feed. In this review we summarize HILIC methods recently developed for drug analysis (2006–2011). In addition, a list of important applications is provided, including experimental conditions and a brief summary of results. The references provide a comprehensive overview of current HILIC applications in drug analysis.

Rapid and sensitive spectrofluorimetric determination of enrofloxacin, levofloxacin and ofloxacin with 2,3,5,6-tetrachloro-p-benzoquinone

A highly sensitive spectrofluorimetric method was developed for the first time, for the analysis of three fluoroquinolones (FQ) antibacterials, namely enrofloxacin (ENR), levofloxacin (LEV) and ofloxacin (OFL) in pharmaceutical preparations through charge transfer (CT) complex formation with 2,3,5,6-tetrachloro-p-benzoquinone (chloranil,CLA). At the optimum reaction conditions, the FQ-CLA complexes showed excitation maxima ranging from 359 to 363nm and emission maxima ranging from 442 to 488nm. Rectilinear calibration graphs were obtained in the concentration range of 50-1000, 50-1000 and 25-500ngmL(-1) for ENR, LEV and OFL, respectively. The detection limit was found to be 17ngmL(-1) for ENR, 17ngmL(-1) for LEV, 8ngmL(-1) for OFL, respectively. Excipients used as additive in commercial formulations did not interfere in the analysis. The method was validated according to the ICH guidelines with respect to specificity, linearity, accuracy, precision and robustness. The proposed method was successfully applied to the analysis of pharmaceutical preparations. The results obtained were in good agreement with those obtained using the official method; no significant difference in the accuracy and precision as revealed by the accepted values of t- and F-tests, respectively.

Methods for the analysis of fluoroquinolones in biological fluids

Methods for the analysis of ten selected fluoroquinolone antibiotics in biological fluids are reviewed. Approaches for sample preparation, detection methods, limits of detection and quantitation, and recovery information are provided for both single analyte and multi-analyte fluoroquinolone methods.

Bioanalytical hydrophilic interaction chromatography: recent challenges, solutions and applications

Hydrophilic interaction chromatography (HILIC) has, in recent years, been shown to be an important supplement to reversed-phase liquid chromatography for polar analytes. HILIC, in conjunction with tandem mass spectrometry (MS/MS), has been steadily gaining acceptance in the analysis of polar compounds from complex biological matrices. This hyphenated technique offers the advantages of improved sensitivity by employing high organic content in the mobile phase, shortened sample preparation time with direct injection of the organic-solvent extracts of biological samples and the potential for ultra-fast analysis because of low-column backpressure. This article reviews recent challenges presented by HILIC, advancements in the better understanding of retention characteristics of analytes with different mobile- and stationary-phase compositions and solutions to ion suppression and interference problems encountered in HILIC–MS/MS assays. Applications of HILIC–MS/MS are summarized, including those for pharmacokinetic studies, metabolic studies, therapeutic drug monitoring and clinical diagnostics.

Separation efficiencies in hydrophilic interaction chromatography

Hydrophilic interaction chromatography (HILIC) is important for the separation of highly polar substances including biologically active compounds, such as pharmaceutical drugs, neurotransmitters, nucleosides, nucleotides, amino acids, peptides, proteins, oligosaccharides, carbohydrates, etc. In the HILIC mode separation, aqueous organic solvents are used as mobile phases on more polar stationary phases that consist of bare silica, and silica phases modified with amino, amide, zwitterionic functional group, polyols including saccharides and other polar groups. This review discusses the column efficiency of HILIC materials in relation to solute and stationary phase structures, as well as comparisons between particle-packed and monolithic columns. In addition, a literature review consisting of 2006-2007 data is included, as a follow up to the excellent review by Hemström and Irgum.

Development and validation of a selective and sensitive bioanalytical procedure for the quantitative determination of gaboxadol in human plasma employing mixed mode solid phase extraction and hydrophilic interaction liquid chromatography with tandem mass spectroscopic detection

A selective and sensitive hydrophilic interaction liquid chromatography tandem mass spectrometric bioanalytical method for the quantitative determination of gaboxadol in human heparinized plasma was developed and validated. Gaboxadol and the stable isotope labeled internal standard were extracted from plasma by mixed mode solid phase extraction and analyzed on an Asahipak NH2P HPLC column with a mobile phase composed of 70% acetonitrile and 30% ammonium acetate (20 mM, pH 4). The analytes were detected by a SCIEX API 4000 triple quadropole instrument using turbo electrospray ionization and multiple reaction monitoring negative mode. The method was validated over the concentration range of 0.5-100 ng/mL. The intra-day precision of the assay, as measured by the coefficient of variation (CV%), was within 4%. The intra-day assay accuracy was found to be within 2.2% of the nominal concentration for all the standards. The average recovery of gaboxadol was about 87% and the ion suppression was approximately 8%. To eliminate late eluters including the glucuronides, a "front cut" column switching procedure was added to the chromatographic system. The effectiveness of the column switching in eliminating the absolute matrix effect caused by late eluters was demonstrated by the low variation (CV<3.5%) in the peak areas of the internal standard during the assessment of the inter-day precision and accuracy and no significant relative matrix effect was observed as illustrated by the excellent intra-day precision (CV<1.5%) from the assessment of standard samples prepared in five different lots of control plasma. The described bioanalytical method has been successfully utilized for the analysis of gaboxadol in post-dose samples (>8000) from various clinical studies. Inter-day precision and accuracy were assessed from the daily mean (n=2) of QC values from 52 runs, i.e. more than 3000 samples. The inter-day precision of the assay, based on the coefficient of variation of QC, ranged from 2.1 to 5.1%. The inter-day assay accuracy was found to be within 4% of the nominal concentration for all QC samples.