Spectrofluorometric determination of certain quinolone through charge transfer complex formation

Spectrophotometric studies of low-cost method for determination of ceftriaxone using a novel charge transfer acceptor, N-(2,4-dinitro-1-naphthyl)-p-toluenesulphonamide

Background

This study reports a new, cost-effective and validated method for the determination of ceftriaxone (CFR). The method involved charge transfer (CT) complexation reaction of ceftriaxone (as n-electron donor) and N-(2,4-dinitro-1-naphthyl)-p-toluenesulphonamide {N-(2,4-DN1NL) PTS} as π-electron acceptor to form a complex. Ultraviolet, infrared and 1H NMR spectra of CFR, N-(2,4-DN1NL) PTS and adduct were then studied to predict the site of interaction between the donor and acceptor.

Result

The complex formed had deep golden-yellow colour, having a new absorption band at 440 nm. Molar absorptivity of 1.667 × 105 L M−1 cm−1 was obtained. The complexation reaction was completed at 30 °C optimal temperature within 10 min. Acetonitrile was found to be the best diluting solvent for optimal detector response and the complex was stable (absorbance unchanged) at room temperature for hours. At concentration of 1.708–11.956 µg mL−1, with low limits of detection of 0.143 µg mL−1, Beer’s law was observed. Between-day recovery statistics of CFR from quality control samples were 102.15 ± 0.062 (% RSD = 0.61, n = 12) over three days. The site of interaction of donor and acceptor molecules, as revealed through infrared (IR) and proton nuclear magnetic resonance studies (1H NMR) and the formation of charge transfer complex is through intermolecular hydrogen bonding between the amino group of the donor and the acidic proton of the acceptor. Common tablet excipients, as observed, did not interfere with the analytical method and no significant difference existed between the results of this new method and the high performance liquid chromatographic procedures (p > 0.05) documented in the USP. The new CT procedure described in this paper is not only simple but also fast, accurate and precise. Also, the reactions were carried out at room temperature compared to previously described procedures.

Conclusions

This novel method could therefore be adopted as a fast but cost-effective alternative for the qualitative and quantitative assessment of CFR in its pure and dosage form. It could find usefulness in on-the-spot detection of counterfeit drugs and in field inspections with reliable accurate results that compares with established methods.

Fiberoptic-Coupled Spectrofluorometer with Array Detection as a Process Analytical Chemistry Tool for Continuous Flow Monitoring of Fluoroquinolone Antibiotics

Nowadays, there is an increasing need for sensitive real-time measurements of various analytes and monitoring of industrial products and environmental processes. Herein, we describe a fluorescence spectrometer in continuous flow mode in which the sample is fed to the flow cell using a peristaltic pump. The excitation beam is introduced to the sample chamber by an optical fiber. The fluorescence emitted upon excitation is collected at the right angle using another optical fiber and then transmitted to the fluorescence spectrometer which utilizes an array detector. The array detection, as a key factor in process analytical chemistry, made the fluorescence spectrometer suited for multiwavelength detection of the fluorescence spectrum of the analytes. After optimization of the experimental parameters, the system has been successfully employed for sensitive determination of four fluoroquinolone antibiotics such as ciprofloxacin, ofloxacin, levofloxacin, and moxifloxacin. The linear dynamic ranges of four fluoroquinolones were between 0.25 and 20 μg·mL-1, and the detection limit of the method for ciprofloxacin, ofloxacin, levofloxacin, and moxifloxacin were 81, 36, 35, and 93 ng·mL-1, respectively. Finally, the proposed system is carried out for determination of fluoroquinolones in some pharmaceutical formulations.

Structure elucidation and degradation kinetic study of Ofloxacin using surface enhanced Raman spectroscopy

A simple, fast and sensitive surface enhanced Raman spectroscopy (SERS) method for quantitative determination of fluoroquinolone antibiotic Ofloxacin (OFX) is presented. Also the stability behavior of OFX was investigated by monitoring the SERS spectra of OFX after various degradation processes. Acidic, basic and oxidative force degradation processes were applied at different time intervals. The forced degradation conditions were conducted and followed using SERS method utilizing silver nanoparticles (Ag NPs) as a SERS substrate. The Ag NPs colloids were prepared by reduction of silver nitrate using polyethyelene glycol (PEG) as a reducing and stabilizing agent. Validation tests were done in accordance with International Conference on Harmonization (ICH) guidelines. The calibration curve with a correlation coefficient (R=0.9992) was constructed as a relationship between the concentration range of OFX (100-500ng/ml) and SERS intensity at 1394cm^-1 band. LOD and LOQ values were calculated and found to be 23.5ng/ml and 72.6ng/ml, respectively. The developed method was applied successfully for quantitation of OFX in different pharmaceutical dosage forms. Kinetic parameters were calculated including rate constant of the degradation of the studied antibiotic.

Positively charged carbon nanoparticulate/sodium dodecyl sulphate bilayer electrode for extraction and voltammetric determination of ciprofloxacin in real samples

The modified electrode was prepared using a layer-by-layer method with functionalized CNPs and SDS. The ability of modified electrode to adsorb ciprofloxacin was investigated. Ciprofloxacin was analyzed in real samples.

Micellar liquid chromatographic method for the simultaneous determination of Levofloxacin and Ambroxol in combined tablets: Application to biological fluids

BACKGROUND

Levofloxacin hemihydrate (LEV) and ambroxol HCl (AMB) are available for the treatment of upper and lower respiratory tract infections. A survey of the literature reveals that two reversed phase HPLC methods were e reported for the simultaneous determination of LEV and AMB in pharmaceutical preparations. However the reported methods suffers from the low sensitivity, no application of the method in the combined tablets and no application to biological fluids. Also the toxic effects of the used solvents which are harmful to human beings. For this reason, our target was to develop a simple sensitive, less hazardous micellar HPLC method for the simultaneous determination of LEV and AMB in their combined dosage forms and plasma.

RESULTS

The method showed good linearity over the ranges of 1-44 μg/mL and 1-20 μg/mL with limits of detection 0.26 and 0.07 μg/mL and limits of quantification 0.80 and 0.20 μg/mL for LEV and AMB, respectively. The method was further extended to the determination of LEV in spiked human plasma with mean percentage recoveries of 100.10% ± 1.14 as well as determination of LEV in real human plasma without prior extraction. Statistical evaluation of the data was performed according to ICH Guidelines.

CONCLUSION

The suggested method was successfully applied for the simultaneous analysis of the studied drugs in their co-formulated tablets and human plasma. The mean percentage recoveries in combined tablets were 100.20 ± 1.64 and 100.72 ± 1.11 for LEV and AMB, respectively and 100.10 ± 1.14 for LEV in spiked human plasma. Statistical comparison of the results with those of the comparison method revealed good agreement and proved that there were no significant difference in the accuracy and precision between the two methods respectively.

Aluminium sensitized spectrofluorimetric determination of fluoroquinolones in milk samples coupled with salting-out assisted liquid-liquid ultrasonic extraction

An aluminium sensitized spectrofluorimetric method coupled with salting-out assisted liquid-liquid ultrasonic extraction for the determination of four widely used fluoroquinolones (FQs) namely norfloxacin (NOR), ofloxacin (OFL), ciprofloxacin (CIP) and gatifloxacin (GAT) in bovine raw milk was described. The analytical procedure involves the fluorescence sensitization of aluminium (Al(3+)) by complexation with FQs, salting-out assisted liquid-liquid ultrasonic extraction (SALLUE), followed by spectrofluorometry. The influence of several parameters on the extraction (the salt species, the amount of salt, pH, temperature and phase volume ratio) was investigated. Under optimized experimental conditions, the detection limits of the method in milk varied from 0.009 μg/mL for NOR to 0.016 μg/mL for GAT (signal-to-noise ratio (S/N)=3). The relative standard deviations (RSD) values were found to be relatively low (0.54-2.48% for four compounds). The calibration graph was linear from 0.015 to 2.25 μg/mL with coefficient of determinations not less than 0.9974. The methodology developed was applied to the determination of FQs in bovine raw milk samples. The main advantage of this method is simple, accurate and green. The method showed promising applications for analyzing polar analytes especially polar drugs in various sample matrices.

Determination of ethambutol by a sensitive fluorescent probe

The competitive reaction between ethambutol and two fluorescent probes (i.e., berberine and palmatine) for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by spectrofluorometry. The CB[7] reacts with these probes to form stable complexes, and the fluorescence intensity of the complexes is greatly enhanced. In addition, the excitation and emission wavelengths of their complexes moved to wavelengths of 343 nm and 495 nm, respectively. However, the addition of ethambutol dramatically quenches the fluorescence intensity of the two complexes. Accordingly, a couple of new fluorescence quenching methods for the determination of ethambutol were established. The methods can be applied for quantifying ethambutol. A linear relationship between the fluorescence quenching values (ΔF) and ethambutol concentration exists in the range of 5.0-1000.0 ng mL(-1), with a correlation coefficient (r) of 0.9997. The detection limit is 1.7 ng mL(-1). The fluorescent probe of berberine has higher sensitivity than palmatine. This paper also discusses the mechanism of fluorescence indicator probes.

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.

Simultaneous determination of proline and pipemidic acid in human urine by capillary electrophoresis with electrochemiluminescence detection

Pipemidic acid is extensively used in the treatment of Gram-negative urinary tract infections, and the contents of proline in human urine vary in association with chronic uremia. The simultaneous determination of pipemidic acid and proline in human urine is of significance for quality control of the dosage and clinical study. The coupling of Ru(bpy)(3)(2+)-based electrochemiluminescence detection with capillary electrophoresis was developed for the simultaneous determination of proline and pipemidic acid in human urine. Parameters related to the separation and detection were investigated and optimized. The standard curves were linear between 0.1 and 90 µg mL(-1) for proline and between 0.4 and 100 µg mL(-1) for pipemidic acid. Underoptimized conditions, the detection limits (3σ) were 0.02 µg mL(-1) for proline and 0.06 µg mL(-1) for pipemidic acid. Relative standard derivations for the electrochemiluminescence intensity and the migration time were 3.2 and 0.9% for proline and 3.7 and 1.2% for pipemidic acid, respectively. The developed method was successfully applied to determine proline and pipemidic acid in human urine. The result showed that the content and decreasing rates of proline in urine for male were higher than that for female, and the content and decreasing rate of pipemidic acid in urine for male and female were consistent, respectively.

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.

Highly sensitive spectrofluorimetric determination of lomefloxacin in spiked human plasma, urine and pharmaceutical preparations

A sensitive, simple and selective spectrofluorimetric method was developed for the determination of lomefloxacin in biological fluids and pharmaceutical preparations. The method is based on the reaction between the drug and 4-chloro-7-nitrobenzodioxazole in borate buffer of pH 8.5 to yield a highly fluorescent derivative that is measured at 533 nm after excitation at 433 nm. The calibration curves were linear over the concentration ranges of 12.5-625, 15-1500 and 20-2000 ng/mL for plasma, urine and standard solution, respectively. The limits of detection were 4.0 ng/mL in plasma, 5.0 ng/mL in urine and 7.0 ng/mL in standard solution. The intra-assay accuracy and precision in plasma ranged from 0.032 to 2.40% and 0.23 to 0.36%, respectively, while inter-assay accuracy and precision ranged from 0.45 to 2.10% and 0.25 to 0.38%, respectively. The intra-assay accuracy and precision estimated on spiked samples in urine ranged from 1.27 to 4.20% and 0.12 to 0.24%, respectively, while inter-assay accuracy and precision ranged from 1.60 to 4.00% and 0.14 to 0.25%, respectively. The mean recovery of lomefloxacin from plasma and urine was 98.34 and 98.43%, respectively. The method was successfully applied to the determination of lomefloxacin in pharmaceuticals and biological fluids.

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.

Utility of 7,7,8,8-tetracyanoquinodimethane charge transfer reagent for the spectrophotometric determination of trazodone, amineptine and amitriptyline hydrochlorides

A simple and rapid spectrophotometric method has been developed for the determination of tricyclic anti-depressant drugs such as trazodone (TZH), amineptine (APH) and amitriptyline (ATPH) hydrochlorides in pure form and in different pharmaceutical preparations. The charge transfer (CT) reaction between TZH, APH and ATPH as electron donors and TCNQ as electron acceptor was utilized for their spectrophotometric determination. The optimum experimental conditions, like time, temperature, stoichiometry, solvents, for the CT complex formation are established. The method permits the determination of TZH, APH and ATPH over a concentration range of 10-400, 10-440 and 10-300 microg ml(-1), respectively. The sensitivity (S) is found to be 0.09, 0.087 and 0.069 g cm(-2) for TZH, APH and ATPH, respectively. The SD values are found to be 0.146-0.293, 0.154-0.285 and 0.091-0.212 and RSD values are 0.142-1.92, 0.297-1.92 and 0.212-0.915 for TZH, APH and ATPH, respectively. The low values of the relative standard deviation indicate the high accuracy and precision of the method. The mean recovery values obtained together with a high correlation coefficient values, amount in the range 98-101.5, 98.7-102.9 and 93-101.9 for TZH, APH and ATPH, respectively. The method is applicable for the assay of the investigated drugs in different dosage forms and the results are in good agreement with those obtained by the official method.

Separation of seven fluoroquinolones by microemulsion electrokinetic chromatography and application to ciprofloxacin, lomefloxacin determination in urine

A simple, reliable microemulsion electrokinetic chromatography (MEEKC) method is developed for the simultaneous separation of seven fluoroquinolones (FQs). The best separation is achieved in a carrier electrolyte containing 1% (v/v) heptane, 100 mmol/L sodium dodecyl sulfate (SDS), 10% (v/v) 1-butanol, and 8 mmol/L phosphate-sodium tetraborate buffer at pH 7.30. The proposed method was directly applied to the determination of ciprofloxacin (CPF) and lomefloxacin (LMF) in urine samples of subjects administered either with CPF or LMF.

Fluoroquinolone antibiotics in the environment

Fluoroquinolones (FQs) are used in large amounts for human and animal medical care. They are excreted as parent compound, as conjugates, or as oxidation, hydroxylation, dealkylation, or decarboxylation products of the parent compound. A considerable amount of FQs and their metabolites may reach the soil as constituents of urine, feces, or manure. The residues of FQs in foods of animal origin may pose hazards to consumers through emergence of drug-resistant bacteria. FQs bind strongly to topsoil, reducing the threat of surface water and groundwater contamination. The strong binding of FQs to soil and sediments delays their biodegradation and explains the recalcitrance of FQs. Wastewater treatment is an efficient elimination step (79%-87% removal) for FQs before they enter rivers. FQs are susceptible to photodegradation in aqueous medium, involving oxidation, dealkylation, and cleavage of the piperazine ring.

Spectrophotometric determination of trazodone, amineptine and amitriptyline hydrochlorides through ion-pair formation with molybdenum and thiocyanate

Extraction spectrophotometric method has been developed for the determination of tricyclic drugs such as trazodone (TZH), amineptine (APH) and amitriptyline (ATPH) hydrochlorides in pure form and in the dosage forms coming from different Egyptian markets. The method based on the formation of ion-pairs between these drugs under investigation and inorganic complex of Mo(V)-thiocyanate followed by its extraction with methylene chloride. The optimum conditions for the ion-pairs formation are established. The method permits the determination of TZH, APH and ATPH over the concentration range of 2-28, 2-32 and 1-30 microg ml(-1), respectively. The Sandell sensitivity (S) is found to be 0.105, 0.138 and 0.118 g cm(-2) for TZH, APH and ATPH, respectively. The SD is found to be 0.16-0.377, 0.12-0.259 and 0.091-0.286 and the R.S.D. are 0.14-0.55, 0.12-0.399 and 0.095-0.485 for TZH, APH and ATPH, respectively. The method is applicable for the assay of the investigated drugs in different dosage forms and the results are in good agreement with those obtained by the official method.

Spectrofluorimetric study on the inclusion interaction between lomefloxacin and p-sulfonated calix[4]arene and its analytical application

The characteristics of host-guest complexation between p-sulfonated calix[4]arene (SC4A) and lomefloxacin (LMFX) were investigated by fluorescence spectrometry. A 1:1 stoichiometry for the complexation was established and an association constant of 6.48x10(4) l mol-1 at 25 degrees C was calculated by applying a deduced equation. The interaction mechanism of the inclusion complex was discussed and the various factors affecting the inclusion process were examined in detail. It was found that an appropriate amount of cationic surfactant cetyltrimethylammonium bromide (CTAB) can remarkably enhance the fluorescence intensity of the supramolecular complex system. Based on the obtained results, a novel sensitive spectrofluorimetric method for the determination of lomefloxacin based on supramolecular complex was developed with a linear range of 0.01-3.0 microg ml-1 and a detection limit of 0.008 microg ml-1, for the first time. The method was applied for the determination of lomefloxacin in pharmaceutical preparations successfully.

Investigation of chromatographic conditions for the separation of ofloxacin and its degradation products

A sensitive, precise, and accurate reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for simultaneous determination of fluoroquinolone antibacterial ofloxacin and its degradation products: decarboxy ofloxacin, 9-piperazino ofloxacin, des-methyl ofloxacin, and ofloxacin-N-oxide. The proposed RP-HPLC method allowed separation of all five compounds simultaneously with the total time of the analysis not more than 15 min. The relative standard deviation (RSD) values for quantification of DOF, POF, MOF, OF, and NOF were of 0.77, 0.58, 0.51, 0.10, and 0.70%, respectively, indicating a good precision of the method. The limits of detection for DOF, POF, MOF, OF, and NOF were 0.10, 0.13, 0.06, 0.03, and 0.03 microg mL(-1), respectively. The described method can be used for simultaneous identification and quantification of all analysed compounds in different pharmaceutical formulations.

Validation of a novel HPLC sorbent material for the determination of ten quinolones in human and veterinary pharmaceutical formulations

A novel sorbent material of ultrapure silica gel provided with novel State of the Art Bonding- and Endcapping Technology commercially available under the name PerfectSil Target (250 x 4 mm, ODS-3, 5 microm, by MZ-Analysentechnik, Germany) was used and validated for the sensitive HPLC determination of ten quinolone antibiotics: enoxacin, ofloxacin, norfloxacin, ciprofloxacin, danofloxacin (DAN), enrofloxacin (ENR), sarafloxacin, oxolinic acid (OXO), nalidixic acid (NAL), and flumequine. The analytical column validation was performed in terms of separation efficiency, precision, and peak asymmetry. The separation was achieved at ambient temperature using a mobile phase of TFA (0.1%)-CH3OH-CH3CN delivered under the optimum gradient program, at a flow rate of 1.2 mU/min. Photodiode array detection was used and eluant was monitored at 275 nm. For the quantitative determination caffeine (7.5 ng/microL) was used as internal standard. The achieved LODs were 0.03 ng/microL per 50 microL injected volume for OXO, 0.1 ng/microL for DAN, ENR, and NAL, and 0.2 ng/microL for the remaining six studied quinolones. The method was validated in terms of interday (n = 6) and intraday (n = 5) precision and accuracy. The proposed method was successfully applied to the analysis of pharmaceutical formulations destined either for human or for veterinary use.