Competitive sorption and desorption behavior for three fluoroquinolone antibiotics in a wastewater treatment wetland soil

Significant amounts of pharmaceuticals are discharged into the environment through wastewater effluent. Sorption has been shown to be a significant aqueous removal pathway for many of these compounds. Competition between ciprofloxacin (CIP), ofloxacin (OFL) and norfloxacin (NOR) and their sorption to, and desorption from, a surrogate Louisiana wastewater treatment wetland soil were investigated to gain insight into the fate and transport of the pollutants within wastewater treatment wetlands. This study was undertaken in the context of a treatment wetland that continuously receives pharmaceuticals. Therefore it is important to understand the total capacity of this soil to sorb these compounds. Sorption to this treatment wetland soil was found to provide a major and potentially long-term removal pathway for these antibiotics from wastewater. LogK(F) values for all three compounds were between 4.09 and 3.90 for sorption and 4.24 and 4.05 microg(1-1/)(n)(cm(3))(1/)(n)g(-1) for desorption. The compounds were sorbed in amounts ranging from 60% to 90% for high and low loading, respectively. The majority of the compounds were sorbed to the soil within the first 20h, indicating that treatment wetland may not need long retention times (weeks to months) in order to remove these compounds. Sorption K(D) values for competition (20 ppm of each compound for 60 ppm of total fluoroquinolones) ranged from 2300 to 3800 cm(3)g(-1) which is between both the 20 (4300-5800 cm(3)g(-1)) and 60 (1300-3000 cm(3)g(-1)) ppm single compound K(D) values, indicating that there is competition between these three compound for sorption sites. Sorption and desorption data (single component and mixture) collectively provide the following evidence: (1) NOR and, to a lesser extent, CIP outcompete OFL for sorption sites, (2) OFL sorbes to its share of "quality" sorption sites, and (3) competition only occurs for lesser "quality" binding sites.

Reduced effect of bromide on the genotoxicity in secondary effluent of a municipal wastewater treatment plant during chlorination

Chlorination of wastewater can form genotoxic, mutagenic, and/or carcinogenic disinfection byproduct (DBPs). In this study, the effect of bromide on genotoxicity in secondary effluent of a municipal wastewater treatment plant during chlorination was evaluated by the SOS/umu test. The presence of bromide notably decreased the genotoxicity in secondary effluent during chlorination, especially under conditions of high ammonia concentration. Bromide significantly decreased the concentration of ofloxacin, a genotoxic chemical in secondary effluent, during chlorination with high concentration of ammonia, while genotoxic DBPs formation of humic acid and aromatic amino acids associated with bromide limitedly contributed to the changes of genotoxicity in secondary effluent under the conditions of this study. By fractionating dissolved organic matter (DOM) in the secondary effluent into different fractions, the fractions containing hydrophilic substances (HIS) and hydrophobic acids (HOA) contributed to the decrease in genotoxicity induced by bromide. Chlorination of HOA without bromide increased genotoxicity, while the addition of bromide decreased genotoxicity.

Determination of ofloxacin and gatifloxacin by mixed micelle-mediated cloud point extraction-fluorimetry combined methodology

A cloud point extraction process using mixed micelle of the anionic surfactant sodium dodecyl sulfate (SDS) and the non-ionic surfactant polyoxyethylene(7.5)nonylphenylether (PONPE 7.5) to extract two fluoroquinolone antimicrobial agents, ofloxacin and gatifloxacin, from aqueous media was investigated. The method is based on the mixed micelle-mediated extraction of fluoroquinolones in the presence of NaCl as an inducing agent in phase separation, followed by spectrofluorimetric determination. The effect of different variables such as pH, PONPE7.5 concentration, SDS concentration, NaCl concentration, cloud point temperature, and time was investigated, and optimum conditions were established. At optimum conditions, the rectilinear calibration graphs were obtained in the concentration range of 0.1-150 and 0.1-250ngmL(-1) for ofloxacin and gatifloxacin, and the limits of detection were 0.04 and 0.06ngmL(-1), respectively. The proposed procedure was applied successfully for the detection of the investigated drugs in their pharmaceutical dosage forms, in spiked plasma, spiked urine, and urine samples, with good precision and accuracy.

A capillary zone electrophoretic method for simultaneous determination of seven drugs in pharmaceuticals and in human urine

A simple, sensitive, and novel method has been developed and validated for the separation and simultaneous quantitation of seven structurally different drugs-pipemidic acid and ofloxacin quinolone antibiotics, pseudoephedrine decongestant, piroxicam anti-inflammatory, thiamin, pyridoxine, and cobalamin-in a mixture by capillary zone electrophoresis. Factors affecting the separation were pH, concentration of buffer, and applied voltage. Separation was carried out in < 9 min with a 50 mM sodium tetraborate buffer, pH 10, and an applied voltage of 30 kV in an uncoated silica capillary tube. The carrier electrolyte gave baseline separation with good resolution, reproducibility, and accuracy. Calibration plots were linear over at least three orders of magnitude of analyte concentrations, and the lower LODs were within the range of 1-5 microg/mL. Detection was performed by UV absorbance at 230 nm. The method was validated for the analysis of drugs in pharmaceutical preparations and in urine samples with RSD of 0.5-2.4% and recovery of > 99%.

Quantitative determination of levofloxacin hemihydrate in bulk and tablets by UV-spectrophotometry and first order derivative methods

Two simple, rapid, accurate and economical 'UV Spectrophotometry' and 'First Order Derivative' methods have been developed for determination of levofloxacin hemihydrate in bulk and tablets. In (10% v/v) acetonitrile, the lambdamax of the drug was found to be 288 nm. The same spectrum was derivatised into first order derivative, using UV probe software of instrument (Shimadzu-2450), at Deltalambda=4. The amplitude of the trough was recorded at 297 nm. In both the proposed methods, levofloxacin hemihydrate follows linearity in the concentration range 2-12 microg/ml with a correlation coefficient of 0.9999. Assay results were in good agreement with label claim. The methods were validated statistically and by recovery studies. The relative standard deviation were found to be less than 2% with excellent precision and accuracy.

[Simultaneous analysis of 7 fluoroquinolone residues in chicken muscle by ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry]

A confirmative method of ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) for the simultaneous determination of 7 fluoroquinolone residues (norfloxacin (NOR), ciprofloxacin (CIP), danofloxacin (DAN), enrofloxacin (ENR), ofloxacin (OFL), sarafloxacin (SAR) and marbofloxacin (MAR)) in chicken muscle was developed. The sample was extracted with acidified acetonitrile, defatted with n-hexane, and purified by an HLB solid phase extraction cartridge. The UPLC separation was performed on an ACQUITY UPLC BEH C18 column (50 mm x 2.1 mm, 1.7 microm) utilizing a gradient elution program of acetonitrile and water (containing 0.1% formic acid) as the mobile phase. The identification and quantification were achieved by using ESI-MS/MS in positive ion mode and multiple reaction monitoring (MRM). The linear ranges were from 5 to 100 microg/kg with the correlation coefficients above 0.99 for all the 7 fluoroquinolones. The average recoveries spiked at the 3 concentration levels of 5, 25, 50 microg/kg ranged from 79. 2% to 108.6% with the relative standard deviations of 4.2% - 8.9%. The limits of detection were 0.2 - 1.4 microg/kg. The method was proved to be good reproducibility, high sensitivity, rapid, reliable and suitable for the simultaneous determination of multi-residues of fluoroquinolones in chicken muscle.

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.

[Multi-residue determination of 11 quinolones in chicken muscle by high performance liquid chromatography with fluorescence detection]

A high performance liquid chromatographic (HPLC) method with fluorescence detection was developed for the simultaneous determination of 11 quinolones (QNs) (norfloxacin, ofloxacin, ciprofloxacin, pefloxacin, lomefloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid and flumequine) residues in chicken muscle. The chicken muscle samples were extracted by 10% trichioroacetic acid/acetonitrile (7:3, v/v) twice, diluted and cleaned up by a reversed-phase solid-phase extraction (SPE) cartridge. The QNs were separated on a reversed-phase C18 column (Hypersil BDS-C18) with mobile phase gradient elution (acetonitrile and water as mobile phases) and detected by a fluorescence detector with a wavelength program. The linear ranges of quinolone calibrations were 5-1200 microg/L in chicken muscle with the correlation coefficients more than 0.998. The recoveries for chicken muscle fortified with 11 QNs at three levels were 56%-119% with acceptable intra-batch relative standard deviations (RSD) (0.4%-16.1%) and inter-batch RSD (1.4%-23.0%). The limits of detection (LOD) and limits of quantification (LOQ) were 1-23 microg/kg and 4-40 kg/kg for the 11 QNs, respectively. The sensitivity meets the quantification requirements for the residue analysis.

Sequential determination of norfloxaxin and levofloxacin in the presence of other fluorquinolones using synchronous scanning room-temperature phosphorimetry and Th (IV) as the selective signal inducer

The selective determination of norfloxacin in mixtures with other fluorquinolones was achieved by synchronous scanning solid surface room-temperature phosphorimetry (SSRTP) and Th(NO(3))(4) as selective phosphorescence inducer. The method also allowed the determination of levofloxacin in a sequential way. The optimization of experimental conditions was made through an univariate approach, in order to find the best conditions for norfloxacin phosphorescence, followed by a 2(3) factorial design in order to verify interaction among relevant variables, to check robustness for each variable and to perform final adjustment of parameters. Absolute limit of detection (ALOD) for norfloxacin was 12ng with a linear signal response extending up to 400ng. Under the same experimental conditions set for norfloxacin, the ALOD for levofloxacin was 13ng with linear signal response up to 450ng. Accuracy of the method, using Th (IV) as selective phosphorescence inducer, was evaluated through the analysis of commercial and simulated pharmaceutical formulations with recoveries between 94.4 and 101% for norfloxacin and 95.9 and 103.8% for levofloxacin. The use of Cd (II), a traditional phosphorescence inducer for fluorquinolones, did not allow selective determination of norfloxacin. Further studies indicated the potential application of the method in urine samples.

Study of fluorescence characteristics of the charge-transfer reaction of quinolone agents with bromanil

A spectrofluorimetric method was discussed for the determination of three antibacterial quinolone derivatives, ofloxacin (OFL), norfloxacin (NOR) and ciprofloxacin (CIP) through charge-transfer complexation (CTC) with 2,3,5,6-tetrabromo-1,4-benzoquinone (bromanil, TBBQ). The method was based on the reaction of these drugs as n-electron donors with the pi-acceptor TBBQ. TBBQ was found to react with these drugs to produce a kind of yellow complexes and the fluorescence intensities of the complexes were enhanced by 29-36 times more than those of the corresponding monomers. UV-vis, (1)H NMR and XPS techniques were used to study the complexes formed. The various experimental parameters affecting the fluorescence intensity were studied and optimized. Under optimal reaction conditions, the rectilinear calibration graphs were obtained in the concentration range of 0.021-2.42 microg mL(-1), 0.017-2.63 microg mL(-1) and 0.019-2.14 microg mL(-1) for OFL, NOR and CIP, respectively. The methods developed were applied successfully to the determination of the subject drugs in their pharmaceutical dosage forms with good precision and accuracy compared to official and reported methods as revealed by t- and F-tests.

Cleaning validation of ofloxacin on pharmaceutical manufacturing equipment and validation of desired HPLC method

Inadequate cleaning of a pharmaceutical manufacturing plant or inadequate purging of the individual pieces of equipment used in multi-product manufacturing or equipment not dedicated to individual products may lead to contamination of the next batch of pharmaceutics manufactured using the same equipment. Challenges for cleaning validation are encountered especially when developing sensitive analytical methods capable of detecting traces of active pharmaceutical ingredients that are likely to remain on the surface of the pharmaceutical equipment after cleaning. A method's inability to detect some residuals could mean that either the method is not sensitive enough to the residue in question or the sampling procedure is inadequate. A sensitive and reproducible reversed-phase, high-performance liquid chromatographic method was developed for the determination of ofloxacin in swab samples. The method for determining ofloxacin residues on manufacturing equipment surfaces was validated in regard to precision, linearity, accuracy, specificity, limit of quantification, and percent recovery from the equipment surface, as well as the stability of a potential contaminant in a cleaning validation process. The active compound was selectively quantified in a sample matrix and swab material in amounts as low as 0.55 ng/mL. The swabbing procedure using cotton swabs was validated. A mean recovery from stainless steel plate of close to 85% was obtained. Chromatography was carried out on a pre-packed Merck (Dermstadt, Germany) Lichrospher model 100 Rp-18 (5.0 microm, 250 mm X 4.0 mm) column using a mixture of sodium lauryl sulfate (0.024% aqueous solution), acetonitrile, and glacial acetic acid (500:480:20,v/v) as the mobile phase at a flow rate of 1.5 mL/min with a column temperature of 35 degrees C and 294 nm detection. The assay was linear over the concentration range of 2 ng/mL to 2000 ng/mL (R approximately 0.99998). The method was validated for accuracy and precision. The stability of ofloxacin in the swab samples was also assessed. In regard to the 10-ppm acceptance criteria in the succeeding batch, the calculated limit was 437 microg/cm2 while according to the 0.1% dosing approach the calculated value was 116 microg/cm2. The calculated recovery values from swab samples were below these acceptable limits during three consecutive cleaning trials. This confirms that the desired level of cleanliness is achieved using the current cleaning procedures, which were consequently validated.

NIR spectroscopic investigation of two fluoroquinolones, levofloxacin and ofloxacin, and their tablets for qualitative identification of commercial products on the market

A rapid and nondestructive identification method for ofloxacin (OFLX) and levofloxacin (LVFX) utilizing diffusion reflectance near-infrared (NIR) spectroscopy was developed. An obvious difference in spectral patterns between LVFX that is used for commercial tablets and LVFX HCl that can be purchased as a reagent at a low price was also observed. These quinolones are especially important for use as drugs against bio-terrorism because of their effectiveness against anthrax infection. Therefore, the possibility of a distribution of counterfeit drugs containing LVFX HCl on the market would be expected. NIR spectroscopic analysis would be applicable to on-site quality analysis that can be carried out easily and nondestructively.

Development and validation of column high-performance liquid chromatographic and derivative spectrophotometric methods for determination of levofloxacin and ornidazole in combined dosage forms

The manuscript describes validated reversed-phase column high-performance liquid chromatographic (RP-HPLC) and first-derivative UV spectrophotometric methods for the estimation of levofloxacin (LFX) and ornidazole (ORNI) in combined dosage forms. The RP-HPLC separation was achieved on a Phenomenex C18 column (250 mm x 4.6 mm id, 5 microm) using KH2PO4 buffer (pH 6.8)-methanol-acetonitrile (70 + 15 + 15, v/v/v) mobile phase at a flow rate of 1.5 mL/min and ambient temperature (25 +/- 2 degrees C). Quantification was achieved with photodiode array detection at 295 nm over the concentration range of 1-10 microg/mL for both LFX and ORNI, with mean recovery of 101.7 +/- 0.23 and 99.23 +/- 1.57%, respectively, by the RP-HPLC method. The derivative spectrophotometric method was based on the determination of both the drugs at their respective zero crossing point (ZCP). The first-order derivative spectra were obtained at N = 1 (scaling factor), Deltalambda = 2.0 nm (wavelength interval), and the determinations were made at 310 nm (ZCP of ORNI) for LFX and 295 nm (ZCP of LFX) for ORNI over the concentration range of 2-40 microg/mL for both LFX and ORNI. Mean recovery was 99.46 +/- 0.96 and 100.9 +/- 0.72%, respectively, by the first-derivative UV spectrophotometric method. Standard and sample solutions were prepared with methanol as the solvent in both of the methods. These methods were found to be simple, accurate, precise, and sensitive and were applicable for the simultaneous determination of LFX and ORNI in combined dosage forms.

Stress-activated bioluminescent Escherichia coli sensors for antimicrobial agents detection

A DNA cartridge encoding Photinus pyralis luciferase (luc), lacZ homology extensions and an excisable marker was constructed to facilitate the conversion of Escherichia coli lacZ fusions to luc fusions by lambda Red-mediated recombination. This tool was used to transform a cspA::lacZ strain into a luminescent biosensor for C-group translational inhibitors. Comparison of cspA::lacZ and cspA::luc cells showed native firefly luciferase to be a more rapid and sensitive reporter than beta-galactosidase for chloramphenicol detection. To evaluate the usefulness of a red-shifted variant of P. pyralis luciferase (LucR1) for biosensor development, a single copy translational fusion between the SOS-inducible sulA promoter and the lucR1 gene was inserted at the malP site of the E. coli chromosome. The sulA::lucR1 fusion allowed high signal detection of the quinolone ofloxacin to levels as low as 15% of the minimum inhibitory concentration and could be combined with a cspA::lacZ fusion to yield a biosensor suitable for the independent and dual detection of chloramphenicol and ofloxacin.

The ocular penetration of levofloxacin 1.5% and gatifloxacin 0.3% ophthalmic solutions in subjects undergoing corneal transplant surgery

OBJECTIVE

To compare corneal tissue and aqueous humor concentrations of levofloxacin 1.5% and gatifloxacin 0.3% ophthalmic solutions after topical dosing.

RESEARCH DESIGN AND METHODS

This was a randomized, observer-masked, parallel-group, multicenter study. Fifty-nine subjects undergoing planned penetrating keratoplasty were randomly assigned to receive either levofloxacin 1.5% or gatifloxacin 0.3% as follows: one drop 15 min prior to surgery and a second drop 10 min before surgery. Corneal button and aqueous humor samples were collected during surgery and immediately stored at -70 degrees C. Levofloxacin and gatifloxacin concentrations were determined by high-pressure liquid chromatography and mass spectrometry.

MAIN OUTCOME MEASURES

Corneal tissue and aqueous humor concentrations of levofloxacin and gatifloxacin.

RESULTS

Levofloxacin achieved statistically significantly higher concentrations in both corneal tissue and aqueous humor compared to gatifloxacin in patients undergoing penetrating keratoplasty. In corneal tissue the mean concentration of levofloxacin was 64.8 +/- 123.4 mug/g vs. 7.0 +/- 9.3 mug/g for gatifloxacin (p < 0.0001). Mean aqueous humor concentration of levofloxacin was 0.976 +/- 2.215 mug/mL vs. 0.0523 +/- 0.143 mug/mL for gatifloxacin (p = 0.0002).

CONCLUSIONS

The high concentrations of levofloxacin achievable in corneal tissue with topical dosing suggest that levofloxacin 1.5% should be a useful agent in the treatment of ocular bacterial infections. However, the corneal concentrations achieved in this study may not be representative of concentrations in patients using less frequent dosing.

UV partial least-squares calibration and liquid chromatographic methods for direct quantitation of levofloxacin in urine

Levofloxacin was determined in human urine samples by application of a spectrophotometric multivariate calibration partial least-squares (PLS-1) method. A calibration set consisting of standards was prepared by using a multilevel multifactor experimental design. In order to ensure accurate results, the calibration matrix included a urine sample free of levofloxacin (i.e., urine blank). The components of the calibration matrix were levofloxacin and urine. The concentration of levofloxacin ranged from 0.5 to 16.5 microg/mL. Different urine concentrations were used as the second component of the calibration matrix in order to include the information inherent in the changes in the UV spectrum for urine upon dilution. In addition, a high-performance liquid chromatographic method was proposed. In this method, a Shim-pack amino column was used at ambient temperature with a mobile phase of 25 mM potassium dihydrogen phosphate (pH adjusted to 3.1 with phosphoric acid)-acetonitrile (70 + 30, v/v), and the flow rate was 1 mL/min. UV detection at 293 nm was used for quantitation. The proposed methods were applied to the determination of the dissolution rate for tablets containing levofloxacin. The urinary excretion pattern for the cumulative amount of levoflacin excreted was also calculated.

[Determination of 16 quinolone residues in animal tissues using high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry]

A confirmative method was developed with high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC-MS/MS) to simultaneously detect 16 quinolone residues in animal tissues, which included nalidixinic acid, oxolinic acid, flumequine, norfloxacin, enoxacin, ciprofloxacin, lomefloxacin, danofloxacin, enrofloxacin, ofloxacin, sarafloxacin, difloxacin, marbofloxacin, pefloxacin, sparfloxacin and orbifloxacin. In the method, the 16 residues were extracted with acidified acetonitrile, cleaned-up with hexane, and concentrated with a rotary evaporator. Then the reconstituted sample solution was analyzed using HPLC-MS/MS in positive mode, with a Inertsil C8-3 column as the analytical column. The method was validated at 10, 50 and 100 microg/kg. The validation results were as follows: the linear ranges were from 10 to 100 microg/kg; the overall recoveries were from 62.4% to 102% with the relative standard deviations of 1.4%-11.9%. The method is simple, rapid, and accurate, and its performance could meet the requirements of the domestic and international legislation. The method is applicable to simultaneously confirm multi-residues of quinolones in animal tissues such as chicken muscle, chicken liver and fish muscle.

Resolution of Ofloxacin–Ciprofloxacin and Ofloxacin–Norfloxacin Binary Mixtures by Flow-Injection Chemiluminescence in Combination with Partial Least Squares Multivariate Calibration

A flow-injection chemiluminescence (CL) method is described for the determination of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL), commonly used antibiotics of the fluoroquinolones family. The method is based on the CL reaction of the fluoroquinolones with tris(2,2'-bipyridyl) ruthenium(II) and Ce (IV), in sulfuric acid medium. The maximum CL emission, given at 0.45 min for CIP, at 0.35 min for NOR and at 0.04 min for OFL, respectively, were measured, allowing the simple application of the proposed method to the routine analysis of the antibiotics. The methods were applied to the determination of CIP, NOR and OFL, in several pharmaceutical preparations, with very satisfactory results, and validated by a previously reported HPLC method. The time-resolved equipment allowed the measurement of the kinetic evolution of the chemiluminescence signals. In base to the differences in the kinetic behaviour of ofloxacin with respect to ciprofloxacin and norfloxacin, binary mixtures of the drugs were resolved by using the time-resolved chemiluminescence signals, in combination with first-order partial least-squares (PLS) multivariate calibration.

Development of a monoclonal antibody-based broad-specificity ELISA for fluoroquinolone antibiotics in foods and molecular modeling studies of cross-reactive compounds

A competitive indirect enzyme-linked immunosorbent assay (ciELISA) using monoclonal antibodies (Mabs) having broad specificity for fluoroquinolone (FQ) antibiotics is described. Four FQs, ciprofloxacin (CIP), enrofloxacin (ENR), norfloxacin (NOR), and ofloxacin (OFL), were conjugated to bovine serum albumin for immunogens and to ovalbumin for coating antigens. A Mab C4A9H1 raised against the CIP hapten exhibited high cross-reactivity (35-100%) with 12 of 14 FQs and detected these FQs in a ciELISA below their maximum residue levels (MRLs) with good sensitivity at 50% binding inhibition (IC50). The quantitative structure-activity relationship (QSAR) between Mab C4A9H1 and various FQs by comparative molecular field analysis (CoMFA) showed a high predictive ability with a cross-validation q2 value of 0.866. Using a simple purification process and the broad-specificity ciELISA adapted for analysis of FQs in chicken muscle, chicken liver, honey, shrimp, and whole egg samples demonstrated recoveries of 60-93% for CIP, ENR, NOR, OFL, flumequine, and danofloxacin.

Optimization of levofloxacin analysis by RP-HPLC using multivariate calibration technique

A rapid and sensitive reverse phase high performance liquid chromatographic (RP-HPLC) method for the analysis of levofloxacin from bulk materials, dosage formulations and human serum is described. This isocratic method employs, a Nucleosil, C18 (10 microm, 25 cm x 0.46 cm) column with a mobile phase of water and acetonitrile (6:5), where in phosphoric acid was used to adjust the pH to 2.9 and propylparaben as an internal standard. Optimization of levofloxacin analysis was carried out using multivariate calibration technique and detector response was recorded at five different wave lengths. A linear response (r > 0.9999) was observed in the range of 40 to 10000 ng ml(-1). The method shows good recoveries, intra and inter-day relative standard deviations were less than 1.2 %. Validation parameters as specificity, accuracy and robustness were also determined. The method can conveniently be used for analysis of levofloxacin pharmacokinetic levels in human serum and pharmaceutical formulations.

A pilot study testing whether concentrations of levofloxacin in interstitial space fluid of soft tissues may serve as a surrogate for predicting its pharmacokinetics in lung

Recent observations indicate that pharmacokinetics of beta-lactam antibiotics in the lung can be predicted by the use of concentration versus time profiles in peripheral soft tissues. If this observation is transferred to other classes of antimicrobials, measurement of antimicrobial concentrations in peripheral tissues would enable prediction of the pharmacokinetics of antimicrobials at the site of the respiratory tract infection. We set out to test the hypothesis that concentrations of the fluoroquinolone levofloxacin in the respiratory tract can be predicted on the basis of knowledge of its pharmacokinetics in peripheral soft tissues. After administration of a single intravenous dose of 500mg of levofloxacin, microdialysis was used to describe the concentration versus time profiles of levofloxacin in the interstitial space fluid of lung tissue of patients (n=5) undergoing elective lung surgery. These data were compared with the concentration versus time courses in the interstitial space fluid of skeletal muscle and subcutaneous adipose tissue of healthy volunteers (n=7). The median AUC(0-infinity) of free levofloxacin in lung (2267mg x min/L, 1980-2355) was about 2-fold and 1.5-fold lower compared with skeletal muscle (4381mg x min/L, range 1720-8195) and adipose tissue (3492mg x min/L, range 1323-6420) of healthy controls, respectively. Concentrations in the interstitial space fluid of the lung were descriptively lower compared with corresponding concentrations in peripheral soft tissues. This is in contrast to previous observations made for the class of beta-lactam antibiotics, and indicates that pharmacokinetics of levofloxacin derived from soft tissues may not be used uncritically for prediction of levofloxacin concentrations in the interstitium of the lung.

Determination of selected antibiotics in the Victoria Harbour and the Pearl River, South China using high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

Nine selected antibiotics in the Victoria Harbour of Hong Kong and the Pearl River at Guangzhou, South China, were analyzed using high-performance liquid chromatography-electrospray ionization tandem mass spectrometry. The results showed that the concentrations of antibiotics were mainly below the limit of quantification (LOQ) in the marine water of Victoria Harbour. However, except for amoxicillin, all of the antibiotics were detected in the Pearl River during high and low water seasons with the median concentrations ranging from 11 to 67 ng/L, and from 66 to 460 ng/L, respectively; and the concentrations in early spring were about 2-15 times higher than that in summer with clearer diurnal variations. It was suggested that the concentrations of antibiotics in the high water season were more affected by wastewater production cycles due to quick refreshing rate, while those in the low water season may be more sensitive to the water column dynamics controlled by tidal processes in the river.

Rapid chiral separation and impurity determination of levofloxacin by ligand-exchange chromatography

A sensitive, simple, and accurate method for determination of levofloxacin and its (R)-enantiomer was developed to determine the chiral impurity of levofloxacin in Cravit Tablets material by ligand-exchange high performance liquid chromatography. The effects of different kinds of ligands, concentration of ligands in mobile phase, organic modifier, pH of mobile phase, and temperature on enantioseparation were investigated and evaluated. Chiral separation was performed on a conventional C(18) column, where the mobile phase consisted of a methanol-water solution (containing 10 mmol L(-1)l-leucine and 5 mmol L(-1) copper sulfate) (88:12, v/v) and its flow-rate was set at 1.0 mL min(-1). The conventional C(18) column offers baseline separation of two enantiomers with a resolution of 2.4 in less than 20 min. Thermodynamic data (DeltaDeltaH and DeltaDeltaS) obtained by Van't Hoff plots revealed the chiral separation is an enthalpy-controlled process. The standard curves showed excellent linearity over the concentration range from 0.5 to 400 mg L(-1) for levofloxacin and its (R)-enantiomer. The linear correlation equations are: y=1.33 x 10(5)x+6297 (r=0.9991) and y=1.34 x 10(5)x+3565 (r=0.9997), respectively. The relative standard deviation (RSD) of the method was below 2.3% (n=3).

Determination of ofloxacin, norfloxacin, and ciprofloxacin in sewage by selective solid-phase extraction, liquid chromatography with fluorescence detection, and liquid chromatography–tandem mass spectrometry

A solid-phase extraction (SPE) and liquid chromatographic (LC) method was developed for the determination of selected fluoroquinolone (FQ) drugs including ofloxacin, norfloxacin, and ciprofloxacin in municipal wastewater samples. Extraction of the FQs was carried out with a weak cation exchanger SPE cartridge, the Oasis WCX. The cartridge was washed with water and methanol as a cleanup before the FQs were eluted by a mixture of methanol, acetonitrile, and formic acid. Separation of the FQs was achieved by using a Zorbax SB-C8 column under isocratic condition at a flow rate of 0.2mL/min. Recoveries of the FQs in spiked final effluent samples were between 87 and 94% with a relative standard deviation of less than 6%. Several techniques have been evaluated for the detection of FQs in sewage extracts; they included fluorescence detection and electrospray ionization (ESI) mass spectrometry using either mass-selective detection or tandem mass spectrometry (MS/MS). When they were applied to sewage influent and effluent samples, the LC-MS/MS technique operating in the multiple reaction monitoring (MRM) mode proved to be best suited for the determination of FQs in sewage samples as it provided the highest sensitivity (limit of quantification 5ng/L) and selectivity. The observation of signal suppression (matrix effect) for some FQs in ESI LC-MS and LC-MS/MS is discussed and a solution is proposed. The three FQs were detected in all the sewage samples tested in this work, with median concentrations between 34 and 251ng/L.

Ofloxacin-delivery system of a polyanhydride and polylactide blend used in the treatment of bone infection

We developed a local drug-release system consisting of two biodegradable polymers, poly(sebacic anhydride) (PSA) and poly-D,L-lactide (PLA), for the treatment of chronic osteomyelitis. PSA and PLA were dissolved and blended at different ratios in tetrahydrofuran. Ofloxacin was loaded with an 8:1 weight ratio of the blend to the drug. The ofloxacin-containing beads of the PSA/PLA blend were made by preheating and compressing them in a mold. The in vitro drug release showed that changing the ratio between the two polymers caused the effective ofloxacin-release duration to vary from 6 to 68 days. The ofloxacin-containing beads with 10% PSA and 90% PLA produced an inhibition zone for the bacteria Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa within 89 days of the experiment. The in vivo drug release of the beads in rabbits demonstrated that the average ofloxacin concentration in the local bone was 20.1 +/- 10.3 microg/g, while that in the plasma was 35.6 +/- 18.8 ng/mL, within 8 weeks. Roentgenography, bacterial cultures, and histological examinations showed that the local release of ofloxacin by the beads could cure osteomyelitis in rabbits. Our findings suggested that using PSA/PLA blends with different ratios as carriers for antibiotics might be useful in the treatment of chronic osteomyelitis and in the prophylaxis of bone infection.