Sayed M. Derayea

Validated spectrofluorimetric method for determination of selected aminoglycosides

New, sensitive, and selective spectrofluorimetric method was developed for determination of three aminoglycoside drugs in different dosage forms, namely; neomycin sulfate (NEO), tobramycin (TOB) and kanamycin sulfate (KAN). The method is based on Hantzsch condensation reaction between the primary amino group of aminoglycosides with acetylacetone and formaldehyde in pH 2.7 yielding highly yellow fluorescent derivatives measured emission (471 nm) and excitation (410 nm) wavelengths. The fluorescence intensity was directly proportional to the concentration over the range 10-60, 40-100 and 5-50 ng/mL for NEO, TOB and KAN respectively. The proposed method was applied successfully for determination of these drugs in their pharmaceutical dosage forms.

Enhancement of the sensitivity of valacyclovir and acyclovir for their spectrofluorimetric determination in human plasma

Two rapid, simple and highly sensitive spectrofluorimetric methods have been developed and validated for determination of valacyclovir hydrochloride (VAC) and acyclovir (ACV). The first method is based on measuring the intrinsic fluorescence of VAC or ACV in an aqueous acidic medium (pH 1.3) at 370 nm after excitation at 280 nm. The fluorescence intensity–concentration plots of VAC and ACV were rectilinear over the concentration ranges of 0.4–5.0 and 0.3–4.0 μg ml−1, respectively. The second method was based on the enhancement of the fluorescence intensity using sodium dodecyl sulfate (SDS) as a micellar system in an aqueous acidic medium (pH 1.3). This is the first attempt for enhancement of the sensitivity of these drugs by spectrofluorimetry. The addition of 2% w/v SDS, produced about 2.7 and 2.9 fold enhancements in the relative fluorescence intensity of VAC and ACV, respectively. The linear range for the second method was 0.2–2.5 and 0.1–1.25 μg ml−1, respectively. The proposed methods were successfully applied for determination of VAC and ACV in pharmaceutical preparations without interference from the common excipients. The high sensitivity of the micellar method permits its application for determination of ACV in human plasma with good percentage recovery.

Derivatization of labetalol hydrochloride for its spectrofluorimetric and spectrophotometric determination inhuman plasma: Application to stability study

Two simple, selective and accurate methods were developed for the determination of Labetalol hydrochloride in pure form and pharmaceutical tablets. Both methods are based on derivatization of the studied drug with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBDCl) in alkaline medium (pH7.5).The reaction product was measured spectrofluorimetrically at 540nm after excitation at 476nm (method I) or spectrophotometrically at 480nm (method II). The calibration graphs were rectilinear over the concentration ranges of 0.10-2.0 and 1.0-11.0μgmL-1 for methods I and II, respectively. The proposed methods were successfully applied to the analysis of commercial tablets without interference from common excipients. Furthermore, the spectrofluorimetric method was utilized for the in vitro determination of labetalol in spiked human plasma, with a percent mean recovery (n=3) of 97.80±1.29%. Moreover, the spectrofluorimetric method was extended to examine the stability study of LBT under different stress conditions such as alkaline, acidic, oxidative, photolytic and a thermal degradation.

Specific and highly sensitive spectrofluorimetric method for determination of febuxostat in its tablets and real human plasma. Application to stability studies

A simple, rapid, specific and highly sensitive spectrofluorimetric method has been developed for determination of febuxostat (FEB) in its tablets and real human plasma. The proposed method is based on the investigation of the fluorescence spectral behavior of FEB in an aqueous acidic system. The fluorescence intensity was measured at 400 nm after excitation at 335 nm. The fluorescence–concentration plot was rectilinear over the range 0.5–20.0 ng ml−1, with a limit of detection of 38.9 pg ml−1 and limit of quantification of 117.3 pg ml−1. The high sensitivity of the proposed method permits its application for the determination of FEB in real human plasma with good percentage recovery (81.73 ± 2.61). The application of the proposed method was further extended to stability studies of FEB after exposure to different forced degradation conditions, such as acidic, alkaline and oxidative conditions, according to ICH guidelines. A proposal for the degradation pathways was postulated.

An application of eosin Y for the selective spectrophotometric and spectrofluorimetric determination of mebeverine hydrochloride

Two rapid and simple methods were developed and validated for the selective determination of mebeverine hydrochloride based on a binary complex formation with eosin Y. In the spectrophotometric method, the absorbance of the formed complex was measured at 551 nm. Beers law is obeyed in the range of 1–12 μg ml−1, the calculated formation constant was 3.95 × 105 and the Gibbs free energy change was −3.1 × 103 J mol−1. The spectrofluorimetric method depends on measuring the quenching effect of the drug on the native fluorescence of eosin Y at 540 nm after excitation at 390 nm. At the optimum reaction conditions, the rectilinear calibration graph between the fluorescence quenching values (ΔF) and the drug concentration was obtained in the drug concentration range of 0.2–3.5 μg ml−1. The analytical performance of both methods was fully validated, and the results were satisfactory. The selectivity of the methods was evaluated by studying the interference liability of the co-formulated drugs such as sulpiride, metronidazole, dimethicone and diloxanide. None of them interfered. The methods were applied successfully for the assay of mebeverine hydrochloride in commercial tablets containing the drug alone or in combination with other drugs.

Spectrofluorimetric determination of certain antidepressant drugs in human plasma

BackgroundCertain antidepressant drugs namely Sertraline hydrochloride, Fluoxetine hydrochloride, Paroxetine hydrochloride, Thioridazine hydrochloride and Amineptine hydrochloride were studied throughout this work using spectrofluorimetric method.MethodsThe spectrofluorimetric method is based on the charge-transfer reaction of these drugs as n-electron donors with 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π-electron acceptor. The drug-TCNQ complexes showed excitation maxima ranged from 290-301 nm and emission maxima ranged from 443-460 nm.Results and discussionThe different experimental parameters affecting the formation and stability of the complexes were carefully studied and optimized. The calibration plots were constructed over the range of 50-450 ng mL-1 for Fluoxetine and Sertraline, 50-550 ng mL-1 for Paroxetine, 50-650 ng mL-1 for Thioridazine and 50-750 ng mL-1 for Amineptine. The proposed method was validated according to ICH and USP guidelines with respect to specificity, linearity, accuracy, precision and robustness.ConclusionA simple, reliable, sensitive and selective spectrofluorimetric method has been developed for determination of certain antidepressant. The proposed method was successfully applied to the analysis of the cited drugs in dosage forms. The high sensitivity of the proposed method allows determination of investigated drugs in spiked and real human plasma.

Development and validation of a stability-indicating spectrofluorimetric method for the determination of H1N1 antiviral drug (oseltamivir phosphate) in human plasma through the Hantzsch reaction

A simple and sensitive spectrofluorimetric method has been described and validated for the determination of oseltamivir phosphate (OSP) in its pure form and pharmaceutical dosage forms. The method is based on the reaction of acetylacetone and formaldehyde with the primary amino group of OSP through the Hantzsch reaction, forming a yellow fluorescent dihydropyridine derivative measured spectrofluorimetrically at 475 nm (excitation at 408 nm). At the optimum reaction conditions, the fluorescence intensity concentration plot is rectilinear over the range of 0.4–2.8 μg mL−1. The lower limits of detection and quantitation were 0.08 and 0.24 μg mL−1, respectively. The developed method was successfully applied for determination of OSP in its commercial capsules and suspension with an average percentage recovery of 99.86 ± 1.20 and 98.36 ± 2.42, respectively (n = 5) without interference from common excipients. The proposed method was utilized for in vitro determination of the cited drug in spiked human plasma, with a percent mean recovery (n = 3) of 98.22 ± 1.27%. Furthermore, the proposed method was extended to study the stability of OSP under different stress conditions; such as hydrolysis (acidic and alkaline), oxidation (30% H2O2 v/v), photolysis, (as per ICH guideline Q1B option 1) and a thermal degradation study. Also the developed method was used to investigate the kinetics of the alkaline and acidic degradations of the cited drug.

Spectrophotometric Determination of Nifedipine and Nicardipine in their Pharmaceutical Preparations

A sensitive and selective spectrophotometric method was developed for determination of nifedipine (NIF) and nicardipine (NIC) in their pharmaceutical preparations. The method based on a rapid reduction of the nitro to primary amino groups using zinc dust and hydrochloric acid. The resulting primary aromatic amine was subjected to a condensation reaction with p-dimethyl amino benzaldehyde to produce a yellowish-green color of Schiff’s bases which quantified spectrophotometrically at the absorption maxima of 434 and 441 nm for NIF and NIC, respectively. Beer’s law was obeyed in the concentration ranges 2.0 to 12.0 μg/mL with a limit of quantitation 1.4 and 1.9 μg/mL and the mean percentage recoveries 98.2±0.3 to 99.5±0.3% NIF and NIC, respectively. The proposed methods were successfully applied to assay NIF and NIC in their capsules and tablets.

Spectrofluorimetric and TLC-densitometric methods for a stability indicating assay of valacyclovir hydrochloride in the presence of its degradation product

Two stability-indicating methods were developed and validated for determination of valacyclovir HCl (VAC) in the presence of its degradation product, acyclovir. The first was a TLC-densitometric method, in which chloroform : methanol : ammonia (50 : 14 : 2 v/v/v) was used as a mobile phase. Silica gel 60 F254 was used as a stationary phase and the chromatogram was scanned at 253 nm. Using this chromatographic system, VAC can be readily separated from its degradation product and gives a compact spot at an RF value of (0.55 ± 0.03). The peak area concentration plot is rectilinear over the range 20–300 ng per band. The second method represents the first attempt for spectrofluorimetric determination of VAC. The method was based on the reaction between VAC and 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in an alkaline medium (pH 8.5) to form a highly fluorescent product that was measured at 500 nm after excitation at 465 nm. The fluorescence intensity concentration plot is rectilinear over the range 1–10 μg ml−1. The proposed methods were successfully applied for the determination of VAC in its commercial tablets with average percentage recovery of 100.13 ± 0.33 and 98.50 ± 1.75 for TLC-densitometric and spectrofluorimetric methods, respectively, without interference from common excipients. The results of the proposed methods were statistically analyzed and found to be in accordance with those given by a reported method. In addition the proposed methods were extended to a stability study of VAC, where the drug was exposed to acidic, alkaline, oxidative and photolytic degradation according to ICH guidelines.

New valid spectrofluorimetric method for determination of selected cephalosporins in different pharmaceutical formulations using safranin as fluorophore

A new validated spectrofluorimetric method has been developed for the determination of some cephalosporins namely; cefepime, cefaclor, cefadroxil, cefpodoxime and cefexime. The method was based on the reaction of these drugs with safranin in slightly alkaline medium (pH 8.0), to form ion-association complexes. The fluorescent products were extracted into chloroform and their fluorescence intensities were measured at 544-565 nm after excitation at 518-524 nm. The reaction conditions influencing the product formation and stability were investigated and optimized. The relative fluorescence intensity was proportional to the drug concentration in the linear ranges of 0.15-1.35, 0.35-1.25, 0.35-1.25, 0.20-1.44 and 0.20-1.25 μg/mL for cefepime, cefaclor, cefadroxil, cefpodoxime proxetil and cefexime, respectively. The detection limits were 40, 100, 100, 60 and 70 ng/mL, respectively. The performance of the developed method was evaluated in terms of Students t-test and variance ratio F-test to find out the significance of proposed methods over the reference spectrophotometric method. Various pharmaceutical formulations were successfully analyzed using the proposed method and the results were in good agreement with those of the previously reported methods.