Validated spectrofluorimetric and spectrophotometric methods for the determination of brimonidine tartrate in ophthalmic solutions via derivatization with NBD-Cl. Application to stability study.

Two simple, selective and accurate methods were developed and validated for the determination of brimonidine tartrate (BT) in pure state and pharmaceutical formulations. Both methods are based on the coupling of the drug with 4-chloro-7-nitro-2,1,3-benzoxadiazole in borate buffer (pH 8.5) at 70 °C and measurement of the reaction product spectrophotometrically at 407 nm (method I) or spectrofluorimetrically at 528 nm upon excitation at 460 nm (method II). The calibration graphs were rectilinear over the concentration ranges of 1.0-16.0 and 0.1-4.0 µg/mL with lower detection limits of 0.21 and 0.03, and lower quantification limits of 0.65 and 0.09 µg/mL for methods I and II, respectively. Both methods were successfully applied to the analysis of commercial ophthalmic solution with mean recovery of 99.50 ± 1.00 and 100.13 ± 0.71%, respectively. Statistical analysis of the results obtained by the proposed methods revealed good agreement with those obtained using a comparison method. The proposed spectrofluorimetric method was extended to a stability study of BT under different ICH-outlined conditions such as alkaline, acidic, oxidative and photolytic degradation. Furthermore, the kinetics of oxidative degradation of the drug was investigated and the apparent first-order reaction rate constants, half-life times and Arrhenius equation were estimated. The proposed methods are practical and valuable for routine applications in quality control laboratories for the analysis of BT.

Simultaneous determination of desloratadine and montelukast sodium using second-derivative synchronous fluorescence spectrometry enhanced by an organized medium with applications to tablets and human plasma.

A rapid, simple, and sensitive second-derivative synchronous fluorimetric method has been developed and validated for the simultaneous analysis of a binary mixture of desloratadine (DSL) and montelukast sodium (MKT) in their co-formulated tablets. The method is based on measurement of the synchronous fluorescence intensities of the two drugs in McIlvaine's buffer, pH 2.3, in the presence of carboxy methyl cellulose sodium (CMC) as a fluorescence enhancer at a constant wavelength difference (Δλ) of 160 nm. The presence of CMC enhanced the synchronous fluorescence intensity of DSL by 216% and that of MKT by 28%. A linear dependence of the concentration on the amplitude of the second derivative synchronous fluorescence spectra was achieved over the ranges of 0.10-2.00 and 0.20-2.00 µg/mL with limits of detection of 0.02 and 0.03, and limits of quantification of 0.05 and 0.10 µg/mL for DSL and MKT, respectively. The proposed method was successfully applied for the determination of the studied compounds in laboratory-prepared mixtures and tablets. The results were in good agreement with those obtained with the comparison method. The high sensitivity attained by the proposed method allowed the determination of MKT in spiked human plasma with average % recovery of 100.11 ± 2.44 (n = 3).

Second-derivative synchronous spectrofluorimetric determination of nebivolol hydrochloride and amlodipine besylate in their combined dosage form.

A rapid, simple, accurate and highly sensitive spectrofluorimetric method was developed for the simultaneous analysis of nebivolol hydrochloride (NEB) and amlodipine besylate (AML). The method was based on measuring the synchronous fluorescence intensity of the drugs at Δλ = 40 nm in methanol. Various experimental parameters affecting the synchronous fluorescence of the studied drugs were carefully studied and optimized. The calibration plots were rectilinear over concentration ranges of 0.05-1.5 µg/mL and 0.5-10 µg/mL for NEB and AML with limits of detection (LOD) of 0.010 and 0.051 µg/mL and limits of quantitation (LOQ) of 0.031 and 0.156, respectively. The peak amplitudes ((2) D) of the second derivative synchronous fluorimetry (SDSF) were estimated at 282 nm for NEB and at 393 nm for AML. Good linearity was obtained over the concentration ranges. The proposed method was successfully applied to the determination of the studied compounds in laboratory-prepared mixtures, commercial single and laboratory-prepared tablets. The results were in good agreement with those obtained using the comparison method. The mean percent recoveries were found to be 100.12 ± 0.77 and 99.91 ± 0.77 for NEB and AML, respectively.

Stability-Indicating Spectrofluorimetric Methods for the Determination of Metolazone and Xipamide in Their Tablets. Application to Content Uniformity Testing.

A highly sensitive, simple and rapid stability-indicating spectrofluorimetric method was developed for the determination of metolazone (MET) and xipamide (XPM) in their tablets. The proposed method is based on the measurement of the native fluorescence of MET in methanol at 437 nm after excitation at 238 nm and XPM in alkaline methanolic solution at 400 nm after excitation at 255 nm. The fluorescence-concentration plots were rectilinear over the range of 2.0- 20.0 ng/mL for MET and 0.2- 2.0 µg/mL for XPM, with lower detection limits (LOD) of 0.35 ng/mL and 0.02 µg/mL and a lower quantification limit (LOQ) of 1.05 ng/mL and 0.07 µg/mL for MET and XPM, respectively. The method was successfully applied to the analysis of MET and XPM in their commercial tablets and the results were in good agreement with those obtained using the official and comparison methods, respectively. Furthermore, content uniformity testing of the studied pharmaceutical tablets was also conducted. The application of the proposed method was extended to stability studies of MET and XPM after exposure to different forced degradation conditions, such as acidic, alkaline, oxidative and photolytic degradation conditions, according to ICH Guidelines. Moreover, the method was utilized to investigate the kinetics of the alkaline, acidic and photolytic degradation of MET. The apparent first-order rate constants and half-life times were calculated. Proposals for the degradation pathways for both MET and XPM were postulated.

Micelle-enhanced spectrofluorimetric method for determination of sitagliptin and identification of potential alkaline degradation products using LC-MS.

A novel, quick, simple and highly sensitive spectrofluorimetric method was developed and validated for the determination of sitagliptin (SG) in its pharmaceutical formulations. The proposed method is based on investigation of the fluorescence spectral behavior of sitagliptin in an SDS micellar system. In an aqueous solution of phosphate buffer pH 4.0, the fluorescence intensity of SG in the presence of SDS was greatly enhanced, by 200%, i.e. twofold enhancement. The fluorescence intensity of SG was measured at 300 nm after excitation at 270 nm. The method showed good linearity in the range 0.03-10.0 µg/mL with a good correlation coefficient (r = 0.9998). The limits of detection and quantitation values were 5.31 and 16.1 ng/mL, respectively. The proposed method was successfully applied to the analysis of SG in its single and co-formulated commercial tablets; the results were in good agreement with those obtained using a reference method. Application of the proposed method was extended to stability studies of SG after exposure to different forced degradation conditions according to the ICH guidelines, such as acidic, alkaline, thermal, photo- and oxidative stress. The chemical structure of certain potential degradation products (DPs) were investigated using LC-MS.

Simultaneous determination of aliskiren and hydrochlorothiazide in tablets and spiked human urine by ion-pair liquid chromatography.

An alternative method for analysis of aliskiren (ALI) and hydrochlorothiazde (HCT) in combined dosage forms by ion-pair reversed phase high performance liquid chromatography was developed and validated. The pharmaceutical preparations were analyzed using a C18 column (250 mm x 4.6 mm, 3 microm) with a mobile phase consisting of 25% methanol, 50% sodium monobasic phosphate aqueous solution containing 6 mM tetrabutylammonium bromide and 25% water at pH 7.2. Isocratic analysis was performed at a flow rate of 1 mL/min and a column temperature of 30 degrees C under direct UV detection at 210 nm. Paracetamol was used as internal standard. The validation was performed according to the ICH guidelines. The proposed method was linear over the concentration range of 0.250 to 60 and 0.1 to 10 microg/mL for ALI and HCT, respectively. The limits of detection and quantitation (LOD and LOQ) were 0.075 and 0.198 microg/mL, respectively, for ALI and 0.04 and 0.062 microg/mL, respectively, for HCT. The method proved to be specific, sensitive, precise and accurate with mean recovery values of 101.1 +/- 0.32% and 100.9 +/- 0.41% for ALI and HCT, respectively. The method robustness was evaluated by means of an experimental design. The proposed method was applied successfully to spiked human urine samples with mean recoveries of 98.8 +/- 0.36% and 98.1 +/- 0.21% for ALI and HCT, respectively.

Spectrofluorimetric determination of oseltamivir phosphate through derivatization with o-phthalaldehyde. Application to pharmaceutical preparations with a preliminary study on spiked plasma samples.

A simple and sensitive spectrofluorimetric method has been developed and validated for the determination of oseltamivir phosphate (OST) in pharmaceutical preparations. The method is based on the reaction between oseltamivir phosphate and o-phthalaldehyde in presence of 2-mercapto-ethanol in borate buffer, pH 10.8, to give a highly fluorescent product measured at 450 nm after excitation at 336 nm. The different experimental parameters affecting the development and stability of the reaction product were studied and optimized. The fluorescence intensity-concentration plot is rectilinear over the range 0.05-1.0 µg/mL, with a lower detection limit of 5 ng/mL and limit of quantitation of 16 ng/mL. The developed method was successfully applied to the analysis of the drug in its commercial capsules and suspension, mean recoveries of OST were 99.97 ± 1.67% and 100.17 ± 1.18%, respectively (n = 3). Statistical comparison of the results obtained by the proposed and comparison method revealed no significant difference in the performance of the two methods regarding accuracy and precision. The proposed method was further extended to in vitro determination of the studied drug in spiked human plasma as a preliminary investigation; the mean recovery (n = 3) was 98.68 ± 5.8%. A reaction pathway was postulated.

Concurrent estimation of some co-administered antimicrobial drugs applying conventional and first derivative synchronous fluorescence spectroscopy techniques.

For the estimation of some co-administered antimicrobials, two highly accurate and precise spectrofluorimetric methods were developed. Fluconazole (FLZ) is co-administered with either ciprofloxacin (CPR) or ofloxacin (OFX) for the treatment of certain microbial infections. On the other hand, another antimicrobial drug, vancomycin (VNC) is co-administered with ciprofloxacin (CPR) for peritonitis treatment. In method I, conventional spectrofluorimetry has been introduced for the concurrent quantitative estimation of FLZ in presence of OFX or CPR. While in method II, a first derivative synchronous spectrofluorimetric technique was adapted for quantitation of VNC and CPR co-administered combination. Both of them were utilized for estimation of the considered drugs in raw materials, laboratory prepared mixtures, dosage forms, and biological fluids. Method I was relied on simultaneous measuring of the native fluorescence of FLZ and OFX or CPR without any overlapping between the emission spectra of each binary mixture (FLZ / OFX) and (FLZ / CPR). Fluorescence intensities were measured at 283.0, 483.0 and 436.0 nm after excitation at 262.0, 292.0 and 275.0 nm for FLZ, OFX and CPR, respectively. Method II was utilized the synchronous fluorescence intensity of VNC and CPR in methanol at Δλ = 40 nm. The first derivative synchronous spectra were calibrated at 297.0 nm for VNC and at 379.5 nm for CPR. Different variables influencing conventional and synchronous fluorescence intensities of the four antimicrobials under investigation were precisely optimized. Both methods were successfully investigated for the determination of the studied drugs in plasma. The linear data analysis for the calibration curves reveals a good relationship in the ranges of 1.0-10.0, 0.25-2.5 and 0.06-0.6 µg/mL for FLZ, OFX and CPR for method I with limits of detection 0.144, 0.038 and 0.007 µg/mL and limits of quantitation of 0.437, 0.114 and 0.021 µg/mL for FLZ, OFX and CPR, respectively. Linearity range for method II was 0.5 -10.0 µg/mL for VNC and CPR with detection limits of 0.127 and 0.110 µg/mL and quantitation limits of 0.380 and 0.334 µg/mL for VNC and CPR, respectively. International Council on Harmonization ICH Q2 (R1) Guidelines were followed in the developed methods validation. The achieved outcomes were statistically compared with those found by the reported ones, and no significant difference was observed.

Tracing the influence of caffeine on the pharmacokinetic parameters of three headache relieving pharmaceuticals applying synchronous fluorescence spectroscopy.

A simple, sensitive, and selective first derivative synchronous fluorimetric method was developed and optimized to track the influence of caffeine content in beverages on the pharmacokinetic parameters of three pharmaceuticals used in relieving headache namely, aspirin (ASP), ibuprofen (IBU), and ergotamine tartrate (ERG). A full validation procedure was carried out to impart validity to the proposed method to apply it to biological fluids. The unique dissolving power of micellar solutions was utilized to avoid multiple extraction steps for both thein vitroandin vivoexperiments, aiming to obtain acceptable recoveries and to accomplish sustainability, where 0.1 M sodium dodecyl sulphate (SDS) was used for this purpose. Moreover, the developed bioanalytical method was subjected to full validation to avoid interferences emerging from biological matrices. The greenness of the proposed method was assessed according to the Analytical Eco-Scale and proved to be excellent green carrying a score of 98%.

Determination of oxybutynin in pharmaceuticals via reaction with mixed acids anhydrides: application to content uniformity testing.

Sensitive and simple spectrophotometric (Method I) and spectrofluorimetric (Method II) methods were developed and validated for the determination of oxybutynin HCl (OXB) in its dosage forms. The method was based on the reaction of OXB with malonic acid anhydride in acetic acid anhydride to form a highly yellow colored product that was measured at 375 nm spectrophotometrically. The same reaction product exihibits strong fluorescence that was measured at 440 nm after excitation at 390 nm. The factors affecting formation and stability of the reaction product were carefully studied and optimized, and the reaction mechanism was postulated. The absorbance-concentration plot is rectilinear over the range 4-40 µg/mL with LOD of 1.12 µg/mL and LOQ of 3.39 µg/mL. The fluorescence-concentration plot is rectilinear over the range 0.5-6 µg/mL with LOD of 0.11 µg/mL and LOQ of 0.33 µg/mL. The method was applied to the analysis of commercial tablets Detronin® and Uripan®. Statistical comparison of the results with those of the reference method revealed good agreement and proved that there were no significant difference in the accuracy and precision between the two methods respectively. The study was extended to content uniformity testing.

Simple and sensitive spectrofluorimetric method for the determination of pregabalin in capsules through derivatization with fluorescamine.

A new, simple and sensitive spectrofluorimetric method has been developed for the determination of pregabalin (PG) in capsules. The method is based on the reaction between pregabalin and fluorescamine in borate buffer solution of pH 10 to give a highly fluorescent derivative that is measured at 487 nm after excitation at 390 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence intensity concentration plot was rectilinear over the range of 0.01-0.3 µg mL⁻¹ with a lower detection limit of 0.0017 µg mL⁻¹ and limit of quantitation of 0.005 µg mL⁻¹. The developed method was successfully applied to the analysis of the drug in its commercial capsules. The mean percentage recovery of PG in its capsule was 99.93±1.24 (n = 3). Statistical comparison of the results with those of the comparison method revealed good agreement and proved that there was no significant difference in the accuracy and precision of the two methods. A proposed reaction pathway was postulated.

Stability-indicating micelle-enhanced spectrofluorimetric method for determination of loratadine and desloratadine in dosage forms.

A highly sensitive and simple spectrofluorimetric method was developed for the determination of loratadine (LRT) and desloratadine (DSL) in their pharmaceutical formulations. The proposed method is based on investigation of the fluorescence spectral behaviour of LRT and DSL in a sodium dodecyl sulphate (SDS) micellar system. In aqueous solution of acetate buffer of pH 4.5, the fluorescence intensities of both LRT and DSL were greatly enhanced (240%) in the presence of SDS. The fluorescence intensity was measured at 438 nm after excitation at 290 nm for both drugs. The fluorescence-concentration plots were rectilinear over the range 0.05-2.0 µg/mL for both LRT and DSL, with lower detection limits of 5.13 × 10(-3) and 6.35 × 10(-3) µg/mL for LRT and DSL, respectively. The method was successfully applied to the analysis of the two drugs in their commercial tablets, capsules and syrups, and the results were in good agreement with those obtained with the official or comparison methods. The proposed method is specific for the determination of LRT in the presence of other co-formulated drugs, such as pseudoephedrine. The application of the proposed method was extended to stability studies of LRT and DSL after exposure to different forced degradation conditions, such as acidic, alkaline and oxidative conditions, according to ICH guidelines.

Green and sensitive spectrofluorimetric method for the determination of two cephalosporins in dosage forms.

Using two green and sensitive spectrofluorimetric methods, we quantified two cephalosporins, cefepime (CFM) and cefazolin (CFZ), in raw and pharmaceutical formulations. The first method is based on the reaction between CFM and fluorescamine (borate buffer, pH 8), which yields a highly fluorescent product. After excitation at 384 nm, the fluorescent product emits light at 484 nm. At concentration ranges from 12.0 to 120.0 ng ml-1, the relative fluorescence intensity/concentration curve was linear with a limit of quantification (LOQ) of 2.46 ng ml-1. The second method relied on measuring the CFZ quenching action on acriflavine fluorescence through formation of an ion-associate complex using Britton-Robinson buffer at pH 8. We measured acriflavine fluorescence at 505 nm after excitation at 265 nm. The decrease in acriflavine fluorescence intensity was CFZ concentration-dependent. Using this method, we quantified CFZ in concentrations ranging from 1 to 10 µg ml-1 with a LOQ of 0.48 µg ml-1. We studied and optimized the factors influencing reaction product formation. Moreover, we adapted our methods to the investigation of the mentioned drugs in raw and pharmaceutical formulations with greatly satisfying results. We statistically validated our methods according to International Council on Harmonisation Guidelines. The obtained results were consistent with those obtained with the official high-performance liquid chromatography methods.

Investigation of some univariate and multivariate spectrophotometric methods for concurrent estimation of Vancomycin and Ciprofloxacin in their laboratory prepared mixture and application to biological fluids.

Four simple, rapid, accurate and precise spectrophotometric methods were established and validated in accordance with ICH Q2 (R1) guidelines for the simultaneous determination of Vancomycin (VNC) and Ciprofloxacin (CPR) in their raw materials, laboratory prepared mixtures and pharmaceutics. Method A depends on using first derivative spectrophotometry (D1) where VNC and CPR were resolved at 243.6 and 262.0 nm, respectively. Concerning method B, it is based on utilizing first derivative of ratio spectra (DD1) where determination was performed at the peak maxima at 244.0 nm and 258.0 nm for VNC and CPR, respectively. Two chemometric models were applied for the quantitative analysis of both drugs in their laboratory prepared mixtures, namely, partial least squares (PLS) (method C) and artificial neural network (ANN) (method D). For univariate methods linearity range for both drugs was in the range of 3-30 and 1-10 µg/mL for VNC and CPR, respectively. Multivariate calibration methods using five level, two factor calibration model for the development of 25 mixtures were also applied for the simultaneous estimation of the two drugs in their laboratory prepared mixture using spectral region from 200.0 to 300.0 nm using interval 1 nm. The suggested methods have been successfully extended to the assay of the two studied drugs in laboratory-prepared mixtures and pharmaceuticals with excellent recovery. First derivative spectrophotometry (D1) was also applied for the assay of both analytes in spiked human plasma with good recovery. No interaction with common pharmaceutical additives has been observed which indicate the selectivity of the method. The results obtained were favourably compared with those obtained applying the reported methods. The methods are validated in compliance with the ICH Q2 (R1) guidelines and the measured accuracy and precision are assessed to be within the accepted limits.

Spectrofluorimetric determination of famotidine in pharmaceutical preparations and biological fluids. Application to stability studies.

A simple, economic, selective, and stability indicating spectrofluorimetric method was developed for the determination of famotidine (FMT); is based on its reaction with 9, 10-phenanthraquinone in alkaline medium to give a highly fluorescent derivative measured at 560 nm after excitation at 283 nm. The fluorescence intensity-concentration plot was rectilinear over the concentration range of 50-600 ng/ml with minimum quantification limit (LOQ) of 13.0 ng/ml and minimum detection limit (LOD) of 4.3 ng/ml. The factors affecting the development of the fluorescence intensity of the reaction product were carefully studied and optimized. The method was applied for the determination of FMT in its dosage forms. The stability of the compound was studied, and the proposed method was found to be stability indicating one. The results obtained were in good agreement with those obtained by the official method. Furthermore, the method was applied for the determination of FMT in spiked and real human plasma. The mean % recovery (n = 4) was found to be 99.94 +/- 0.24, and 105.13 +/- 0.64 for spiked and real human plasma, respectively. The composition of the reaction product as well as its stability constant was also investigated. Moreover, the method was utilized to investigate the kinetics of both alkaline and oxidative induced degradation of the drug. The apparent first order rate constant and half life time of the degradation product was calculated. A proposal of the reaction pathway was postulated.

Second-derivative synchronous fluorescence spectroscopy for the simultaneous determination of fluphenazine hydrochloride and nortriptyline hydrochloride in pharmaceutical preparations.

A rapid, simple, and highly sensitive second-derivative synchronous fluorimetric (SDSF) method has been developed for the simultaneous analysis of binary mixtures of fluphenazine hydrochloride (FLZ) and nortriptyline hydrochloride (NTP) in their co-formulated tablets. The method is based upon measurement of the native fluorescence of these drugs at constant wavelength difference (Deltalambda) = 120 nm in acetic acid. The different experimental parameters affecting the fluorescence intensity of the studied drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.25-3.0 and 1-10 microg/ml for FLZ and NTP respectively, with lower detection limits (LOD) of 0.05 and 0.18 microg/ml and quantitation limits of 0.15 and 0.53 microg/ml for FLZ and NTP respectively. The proposed method was successfully applied for the determination of the studied compounds in their synthetic mixtures and in commercial co-formulated tablets. The results obtained were in good agreement with those obtained by the reference methods.

The alternating current polarographic behavior and determination of lansoprazole and omeprazole in dosage forms and biological fluids.

The alternating current (ACt) polarographic behavior of lansoprazole (LNS) and omeprazole (OMP) was studied in Britton Robinson buffers (BRb) over the pH range 4.1-11.5. In BRb of pH 9.6 and 10.5, well-defined ACt peaks were obtained for both LNS and OMP, respectively. The current-concentration plots were rectilinear over the ranges of 0.4-20 microg mL(-1) and 0.2-10 microg mL(-1) for LNS and OMP respectively. The minimum detection limits (S/N=2) were 0.02 microg mL(-1) (5.4x10(-8) M) and 0.01 microg mL(-1) (2.9x10(-8) M) for LNS and OMP, respectively. The proposed method was successfully applied to the analysis of the two drugs in their commercial capsules. The average percent recoveries were favorably compared to those obtained by reference methods. Co-administered drugs such as naproxen and methotrexate did not interfere with the proposed method. The proposed method was further extended to the in-vitro determination of the lansoprazole in spiked plasma, the percentage recoveries was 98.47+/-1.29 (n=4). The pathway for the electrode reaction for both drugs involved reduction of the sulphonyl group into the corresponding thiol group at the Dropping Mercury Electrode. The advantages of the method were time saving and more sensitive than the other published voltammetric method. Yet The present study is the first report on the use of alterating current polarography (ACt) in this respect.

Method development and validation for the simultaneous determination of cinnarizine and co-formulated drugs in pharmaceutical preparations by capillary electrophoresis.

Rapid and simple capillary electrophoresis (CE) methods were developed for the simultaneous determinations of cinnarizine and domperidone (CN/DOM) and cinnarizine and nicergoline (CN/NIC) in their co-formulated tablets. The optimized CE conditions were as follows: running buffer, methanol-acetate buffer (pH 3.0, 10 mM) (80:20 and 85:15 (v/v) for CN/DOM and CN/NIC, respectively); applied voltage, 20 kV; UV detection wavelengths, 215 and 227 nm for CN/DOM and CN/NIC, respectively; hydrodynamic injection was performed at a height of 25 mm for 30 s. Quinine hydrochloride and nicardipine hydrochloride were used as internal standards for the determination of CN/DOM and CN/NIC, respectively. Calibration curves were linear over the ranges 0.25-20/0.375-15 microg/ml (CN/DOM) and 0.25-25/0.4-10 microg/ml (CN/NIC) in each optimized condition. Detection limits were 0.074/0.119 microg/ml and 0.072/0.116 microg/ml for CN/DOM and CN/NIC, respectively. The proposed methods were successfully applied for the simultaneous determination of both CN/DOM and CN/NIC in their co-formulated tablets without interfering peaks due to the excipients present in the pharmaceutical tablets. The estimated amounts of CN/DOM and CN/NIC were almost identical with the certified values, and their percentage relative standard deviation values (%R.S.D.) were found to be < or =2.34% (n=3).

Differential pulse polarographic determination of ofloxacin in pharmaceuticals and biological fluids.

A sensitive method is described for the determination of ofloxacin in its pure form, dosage forms and biological fluids. The proposed method depends upon the polarographic activity of ofloxacin in Britton Robinson buffers, whereby a well-defined cathodic wave is produced over the pH range 4.1-10.3. The wave was characterized as being irreversible, diffusion-controlled with limited adsorption properties. The current-concentration relationship was found to be rectilinear over the range 5x10(-5)-5x10(-4) M and 1x10(-5)-5x10(-4) M using the DC(t) and DPP modes respectively, with a minimum detectability (S/N=3) of 3x10(-7) M. The proposed method was successfully applied to the determination of ofloxacin in tablets and biological fluids. The results obtained were found to be in agreement with those obtained by a reference method.

Anodic polarographic determination of ciclopirox olamine in pure and certain pharmaceutical preparations.

The anodic polarographic behavior of ciclopirox have been studied in Britton Robinson buffer (BRb) over the pH range 6-11. In BRb of pH 7 a well defined anodic wave was produced with diffusion current constant (Id) of 4.86+/-0.048 (n=6) using DC(t) mode. Adopting both of direct current (DC(t)) and differential pulse polarographic (DPP) modes, the current-concentration relationship was found to be rectilinear over the range 4 to 24 and 2 to 12 microg ml(-1) respectively, with minimum detectability (S/N=2) of 0.2 microg ml(-1) (1 x 10(-6) M) using the DPP mode. The average percent recovery was favourably compared to a reference method, with a satisfactory standard deviation, the proposed method was further applied to the determination of ciclopirox olamine in certain pharmaceutical preparations including lotion and cream. The average percentage recoveries for lotion were 100.06+/-0.94 and 100.06+/-1.08 using DC(t) and DPP modes respectively, and for cream were 100.17+/-0.64 and 100.34+/-1.28 using DC(t) and DPP modes, respectively. A pathway for the electrode reaction was postulated.