Spectrofluorimetric and micelle-enhanced spectrofluorimetric determination of gatifloxacin in human urine and serum

A spectrofluorimetric method to determine gatifloxacin has been developed and applied to the quantification of this fluoroquinolone in spiked human urine and serum. The native fluorescence of gatifloxacin allow the determination of 0.040-0.700 micro gmL(-1) of this molecule in aqueous solution containing acetic acid-sodium acetate buffer (pH 3.5), with lambda(exc)=292 nm and lambda(em)=484 nm. Micelle-enhanced fluorescence led to 75% higher analytical signals in presence of 12 mM sodium dodecyl sulphate, which allow the determination of 0.020-0.450 microg mL(-1) fluoroquinolone with lambda(exc)=292 nm and lambda(em)=470 nm. Both methods were successfully applied to gatifloxacin determination in spiked human urine and serum.     

Spectrophotometric and spectrofluorimetric determination of atomoxetine in pharmaceutical preparations

Visible spectrophotometric and spectrofluorimetric methods were developed for the determination of atomoxetine in pharmaceutical preparations. The spectrophotometric method was based on a nucleophilic substitution reaction of atomoxetine with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium to form an orange-colored product. The absorbance-concentration plot is rectilinear over the range 5-40 microg mL(-1). The limits of detection and quantification were calculated to be 0.02 microg mL(-1) and 0.06 microg mL(-1), respectively. The spectrofluorimetric method was based on the derivatization reaction of 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) with atomoxetine to produce a fluorescent derivative. The formed highly fluorescent derivative that was measured at 462 nm after excitation at 533 nm. The fluorescence-concentration plot is rectilinear over the range 10-500 ng mL(-1). The limits of detection and quantification were calculated to be 0.19 ng mL(-1) and 0.57 ng mL(-1). The analytical performance of both methods was fully validated, and the results were satisfactory. The methods have been successfully applied for the determination of the studied drug in capsules and the results obtained ware in good agreement with those obtained by the reference method.     

Spectrofluorimetric determination of adrenaline and related compounds in pharmaceutical preparations

A simple and rapid method for the spectrofluorimetric determination of adrenaline and some related compounds in pharmaceutical preparations was developed. The method is based on the measurement of the fluorescence of the compounds at their respective emission maxima after excitation of solutions in 0. 1 M sodium dihydrogen phosphate. The influence of several additives (drugs, preservatives, buffers, etc.) was studied. With the method amounts of 1–4g/ml of the various drugs could be determined. The method was tested with a variety of pharmaceutical formulations.In honour of Prof. Dr. M.Langejan on the occasion of her retirement.     

Simultaneous spectrofluorimetric and spectrophotometric determination of melatonin and pyridoxine in pharmaceutical preparations by multivariate calibration methods

Partial least-squares (PLS) calibration and principal component regression (PCR) methods were utilized for the simultaneous spectrofluorimetric and spectrophotometric determination of pyridoxine (PY) and melatonin (MT). Since emission and adsorption spectra of these drugs overlap, PY and MT cannot be directly determined by fluorimetric nor by spectrophotometric methods. Full-spectrum multivariate calibration PLS and PCR methods were developed for both fluorimetry and spectrophotometry. The conditions were optimized for fluorimetric as well as for spectrophotometric determination of both drugs. The simultaneous determination of PY and MT was carried out in mixtures by recording the emission fluorescence spectrum between 324 and 500 nm (lambda(ex) 285 nm) for fluorimetry, and by recording the absorption spectrum between 250 and 350 nm for spectrophotometry (lambda(max(PY)) 310 nm, lambda(max(MT)) 278 nm). The experimental calibration matrixes were designed orthogonally. At the optimum conditions, dynamic ranges were 0.04-1.3 and 0.1-4 microg ml(-1) for fluorimetry and 1-22 and 1-24 microg ml(-1) for spectrophotometry for MT and PY, respectively. The calibration concentrations were prepared in the dynamic ranges. The parameters of the chemometrics procedure for the simultaneous determination of MT and PY were optimized, and the proposed methods were validated with prediction set. Finally the procedures were successfully applied to simultaneous spectrofluorimetric and spectrophotometric determination of PY and MT in synthetic mixtures and in a pharmaceutical formulation.     

Spectrofluorimetric determination of prenalterol hydrochloride in pharmaceutical preparations and biological fluids

A simple and highly sensitive fluorimetric method was developed for the routine determination of prenalterol hydrochloride in bulk, in dosage forms and in biological fluids. The method is based on the fluorescence induced by reaction of the nitroso-derivative of prenalterol hydrochloride with 2-cyanoacetamide in the presence of ammonia. The different experimental parameters were carefully studied and incorporated into the procedure. The fluorescence is measured at 440 nm after excitation at 368 nm. Fluorescence intensity is a linear function of prenalterol hydrochloride concentration over the range of 0.1–2.8 μg ml⁻¹ in the solution finally measured. A proposal for the reaction pathway was suggested.     

Spectrophotometric and spectrofluorimetric methods for the determination of ropinirole content in pharmaceutical dosage forms

Two simple and rapid spectrofluorimetric and spectrophotometric methods were described for the determination of ropinirole hydrochloride content in pharmaceutical dosage forms. Both methods are based on the reaction of ropinirole hydrochloride and eosin Y in aqueous medium at pH 4.0. Quenching of the fluorescence intensity of eosin Y at 540 nm upon excitation at 350 nm was used for the determination of ropinirole hydrochloride levels after ion-pair complex formation. Also, the absorbance increase of eosin Y at 546 nm after ion-pair complex formation was used for spectrophotometric measurements. Both methods showed linear relationships between the fluorescence quenching or absorbance increase and ropinirole concentration in the range of 6–150 µg/mL and 50–500 µg/mL for spectrofluorimetric and spectrophotometric methods, respectively. As no organic solvents were used in these two methods, they could be categorized as green analytical methods. Both methods were accurate (Error<1.2%) and precise (CV<1.9%), as shown by statistical analysis results. Both methods were used for determination of ropinirole hydrochloride content in pharmaceutical dosage forms without any significant interference from associated impurities.     

Spectrofluorimetric and spectrophotometric determination of rosiglitazone maleate in pharmaceutical preparations and biological fluids

Two simple, sensitive and specific methods were developed for the determination of rosiglitazone maleate (ROZ) in pure form, pharmaceutical preparations, and biological fluids. Method I (spectrophotometry) is based on complex formation of (ROZ) with both copper(II) chloride, and aluminum (III) chloride in borate buffer (pH 6.5). The absorbance of the formed complexes was measured at 318 nm. The absorbance- concentration plots were rectilinear over the concentration range of 8 – 80 and 5 – 70 μg/ml, with detection limits of 1.98 and 1.32 μg/ml for Cu(II) and Al(III), respectively. Method II is based on the spectrofluorimetric determination of ROZ through complex formation with Al⁺3 in acetate buffer of pH 5. The relative fluorescence intensity of the formed complex was twice that of the native fluorescence of the drug and was measured at 376 nm after excitation at 318 nm. The fluorescence intensity – concentration plot was rectilinear over the concentration range of 0.03 – 2.0 μg/ml with minimum quantification limit (LOQ) of 0.02 μg/ml and minimum limit of detection (LOD) of 0.01 μg/ml. The factors affecting the complex formation in both methods (I and II) were carefully studied and optimized. Both methods were applied for the determination of ROZ in its tablets. The results obtained were in good agreement with those obtained by the comparison method. Furthermore, method II was applied for the determination of ROZ in spiked and real human plasma, and the mean % recoveries (n = 4) were 97.54 ±0.56, and 97.38±0.93 respectively. The stability of the formed complexes in both methods was studied, and the proposed methods were found to be stability indicating ones. The composition of these complexes as well as their stability constants was also investigated. Moreover, the methods were utilized to investigate the kinetics of alkaline, acidic, and oxidative induced photodegradation of the drug. The apparent first-order rate constant and halflife of the photodegradation products were calculated. Reaction pathways were postulated.     

Simultaneous spectrofluorimetric determination of thiamin, pyridoxine and riboflavin in pharmaceutical multivitamin preparations

Independent spectrofluorimetric methods have been described for the assay of thiamin, pyridoxine and riboflavin in combination. Thiamin determination is based on the spectrofluorimetric measurements of thiochrome formed by the oxidation with N-bromosuccinimide (N-BS) in isopropanol. The method proved to be a stability indicating method. Pyridoxine and riboflavin are estimated by measuring their independent fluorescence in buffer solution pH = 7. The methods are highly specific and can be performed without prior extraction or separation of the individual vitamins. The sensitivity ranges are 1.5-3.5, 0.5-2.5 and 0.4-2.0 micrograms X ml-1 for thiamine, pyridoxine and riboflavin respectively.     

Kinetic methods for the determination of atenolol in pharmaceutical preparations.

The fixed concentration and the fixed time methods were used for quantitative determination of atenolol employing 0.0515 M ammonium meta vanadate as an oxidant in 2.5 M sulphuric acid at 84 degrees C. The two methods are based on reaction rate measurements following the absorbance of vanadium (IV) species produced, spectrophotometrically at 750 nm. The applicability of the methods was tested by assaying atenolol in drug formulations and comparing the results obtained statistically with the BP method.     

Sensitive spectrofluorimetric and spectrophotometric methods for the determination of thonzylamine hydrochloride in pharmaceutical preparations based on coupling with dimethylbarbituric acid in presence of dicyclohexylcarbodiimide

Two sensitive and selective spectrophotometric and spectrofluoimetric procedures were developed for the determination of thonzylamine hydrochloride (THAH) in tablets and nasal drops. The methods are based on K?nig reaction which resulted in an orange-yellow fluorescent product. The orange-yellow product of the interaction between the dicyclohexylcarbodiimide (DCC), THAH and dimethylbarbituric acid (DMBA) showed an absorption maximum at 492 nm, a first-derivative signal at 494 nm and a fluorescence emission peak at 518 nm (lambda(ex)=492 nm). The orange-yellow color was found to be stable for at least 2 h. The reaction conditions were studied and optimized. The reaction obeys Beer's law over the ranges 8-20 and 0.2-2.0 microg ml(-1) for the derivative spectrophotometric and fluorimetric measurements, respectively. The detection limits were found to be 0.29 and 0.018 microg ml(-1) for the spectrophotometric and fluorimetric measurements, respectively. The proposed methods were applied to the analysis of pharmaceutical formulations containing THAH, either alone or in combination with naphazoline nitrate.     

Spectrofluorimetric determination of sulphonamides in pharmaceutical compounds and foods

Spectrofluorimetry and room temperature photochemically-induced fluorescence (RTPF) have been applied to the determination of sulphacetamide (SAC), sulphaguanidine (SG) and sulphamethazine (SMT) in milk and pharmaceutical formulations. The methods are suitable for determining 0.02-0.10 micrograms ml of SAC, 0.10-0.50 micrograms ml of SG, and 0.40-1.00 micrograms of SMT.     

Comparison of two derivative spectrophotometric methods for the determination of alpha-tocopherol in pharmaceutical preparations

Simple, sensitive and reliable derivative spectrophotometric methods were developed and validated for determination of alpha-tocopherol in pharmaceutical preparations. The solutions of standard and the sample were prepared in absolute ethanol. The quantitative determination of the drug was carried out using the first derivative values measured at 284, 304 nm and the second derivative values measured at 288, 296 nm. Calibration graphs constructed at their wavelengths of determination were linear in the concentration range of alpha-tocopherol using peak to zero 10-250 microg ml(-1) for first and second derivative spectrophotometric methods. Developed spectrophotometric methods in this study are accurate, sensitive, precise, reproducible, and can be directly and easily applied to Evon dragee form as pharmaceutical preparation. Statistical analysis (Student's t-test) of the obtained results showed no significant difference between the proposed two methods.     

Spectrophotometric methods for the determination of ritodrine hydrochloride and its application to pharmaceutical preparations

Two simple and sensitive spectrophotometric methods are described for the determination of ritodrine hydrochloride (RTH) in both pure and dosage forms. The methods are based on the interaction of diazotised p-nitroaniline (DPNA) and sulphanilic acid (DSNA) with RTH in an alkaline medium. The resulting azo dyes are measured at 480 nm (for the DPNA method) and at 440 nm (for the DSNA method) and are stable for more than 1 h. The optimum reaction conditions and other analytical parameters are evaluated. A study of the effect of commonly associated excipients and additives do not interfere with the determinations. Statistical analysis of results indicates that the methods are precise and accurate.     

Spectrofluorimetric and spectrophotometric methods for the determination of vigabatrin in tablets

Two sensitive and selective spectrofluorimetric and spectrophotometric methods have been developed for the determination of vigabatrin in tablets. The methods are based on derivatization with 7-chloro-4-nitrobenzofurazan (NBD-Cl). The product showed an absorption maximum at 460 nm and a fluorescence emission peak at 520 nm in ethyl acetate. The color was found to be stable for at least 48 h in this solvent. The optimum conditions of the reaction were investigated and it was found that the reaction proceeds quantitatively at pH 10.0, 70 degrees C in 50 min when the mole ratio of the reagent to drug was 30. The reaction obeys Beer's law over the ranges of 2-10 and 0.05-1.00 microg ml(-1) for the spectrophotometric and spectrofluorimetric measurements, respectively. The detection limits were found to be 0.50 and 0.01 microg ml(-1) for the spectrophotometric and spectrofluorimetric methods, respectively. The proposed methods were applied to the assay of vigabatrin in tablets. The results were compared statistically with those obtained by the modified spectrofluorimetric method reported in the literature.     

Spectrofluorimetric method for determination of citalopram in bulk and pharmaceutical dosage forms

A simple accurate, sensitive reproducible spectrofluorimetric method was developed for the analysis of citalopram in pure and pharmaceutical dosage form. Citalopram showed strong native fluorescence in 0.05 M sulphuric acid having excitation at 239 nm and emission at 300 nm. All parameters like the effect of different solvents, pH, dilutions, reaction time, temperature and effect of excipients were thoroughly investigated. The calibration graph was linear in the range from 0.100 to 0.900 μg/ml. The proposed method was statistically validated and successfully applied for analysis of tablet dosage forms. The percentage recovery was found to be between 99.08% to 99.28%.     

Study of stability of methotrexate in acidic solution spectrofluorimetric determination of methotrexate in pharmaceutical preparations through acid-catalyzed degradation reaction

Study of the degradation reaction of methotrexate (MTX) in acidic solution was carried out. Optimization of the experimental parameters of MTX acid hydrolysis was investigated. Spectrofluorimetric method for determination of MTX through measurement of its acid-degradation product, 4-amino-4-deoxy-10-methylpteroic acid (AMP), was developed. Stability of the standard solution of MTX prepared in sulfuric acid was discussed in the view of accelerated stability analysis. Two other comparative spectroflourimetric methods based on measuring the fluorescence intensities from either a condensation reaction with acetylacetone-formaldehyde (Hantzsch reaction) or a reaction with fluorescamine were also described. Beer's law validation, accuracy, precision, limits of detection, limits of quantification, and other aspects of analytical merit are presented in the text. The proposed methods were successfully applied for the analysis of MTX in pure drug and tablets dosage form. The sensitivity of the developed methods was favorable, so it was possible to be adopted for determination of MTX in plasma samples for routine use in high-dose MTX therapy.