Micelle-enhanced spectrofluorimetric method for determination of lacidipine in tablet form; application to content uniformity testing.

A highly sensitive, simple and rapid spectrofluorimetric method was developed for the determination of lacidipine (LCP) in tablets. The proposed method is based on the investigation of the fluorescence spectral behavior of LCP in both sodium dodecyl sulphate (SDS) and the tween-80 micellar system. In aqueous solutions of acetate buffer (pH 4.5), the fluorescence intensities of LCP were greatly enhanced (ca. 2.4 and 4.3 folds) in the presence of either SDS or tween-80, respectively. The fluorescence intensity was measured at 444 nm after excitation at 277 nm using either SDS or tween-80 as a surfactant. The fluorescence-concentration plots were rectilinear over the ranges of 50.0-500.0 ng/ml and 5.0-200.0 ng/ml with lower detection limits of 5.11 and 2.06 ng/ml and lower quantification limits of 17 and 6.87 ng/ml using SDS and tween-80, respectively. The method was successfully applied to the analysis of LCP in commercial tablets and the results were in good agreement with those obtained with the comparison method. Furthermore, content uniformity testing of pharmaceutical tablets was also conducted.

Novel validated spectrofluorimetric methods for the determination of taurine in energy drinks and human urine.

Two sensitive, selective, economic and validated spectrofluorimetric methods were developed for the determination of taurine in energy drinks and spiked human urine. Method Ι is based on fluorimetric determination of the amino acid through its reaction with Hantzsch reagent to form a highly fluorescent product measured at 490 nm after excitation at 419 nm. Method ΙΙ is based on the reaction of taurine with tetracyanoethylene yielding a fluorescent charge transfer complex, which was measured at λex /em of (360 nm/450 nm). The proposed methods were subjected to detailed validation procedures, and were statistically compared with the reference method, where the results obtained were in good agreement. Method Ι was further applied to determine taurine in energy drinks and spiked human urine giving promising results. Moreover, the stoichiometry of the reactions was studied, and reaction mechanisms were postulated.

Micellar HPLC and derivative spectrophotometric methods for the simultaneous determination of fluconazole and tinidazole in pharmaceuticals and biological fluids.

Micellar high-performance liquid chromatography (HPLC) and first-derivative ultraviolet spectrophotometry were used to simultaneously determine fluconazole (FLZ) and tinidazole (TNZ) in combined pharmaceutical dosage forms. The derivative procedure is based on the linear relationship between the drug concentration and the first derivative amplitudes at 220 and 288 nm for FLZ and TNZ, respectively. The calibration graphs were linear in the range of 1.5-9.0 µg/mL for FLZ and 10.0-60.0 µg/mL for TNZ. Furthermore, an HPLC procedure with ultraviolet detection at 210 nm was developed. For the HPLC procedure, good chromatographic separation was achieved using an ODS C18 column (250 × 4.6 mm i.d.). The mobile phase containing 0.15M sodium dodecyl sulphate, 0.3% triethylamine and 12% n-propanol in 0.02M orthophosphoric acid at pH 5.5 was pumped at a flow rate of 1 mL/min. Indapamide was used as an internal standard. The method showed good linearity over the concentration ranges of 1.5-30.0 and 10.0-200.0 µg/mL, with limits of detection of 0.36 and 2.70 µg/mL and limits of quantification of 1.1 and 8.2 µg/mL for FLZ and TNZ, respectively. The suggested methods were successfully applied for the simultaneous analysis of the drugs in their laboratory prepared mixture, co-formulated tablet and single dosage forms. Moreover the second method was also extended to the determination of the drugs in biological fluids.

Fluorometric determination of bopindolol and celiprolol in pharmaceutical preparations and biological fluids.

Two sensitive fluorometric methods were developed for the determination of both bopindolol malonate (BOP) and celiprolol HCl (CLP) based on measuring their native fluorescence in methanol and acetonitrile, respectively. For BOP, the fluorescence was measured at 316 nm after excitation at 278 nm. The proposed method was successfully applied to the assay of commercial tablets as well as content uniformity testing. For CLP, the fluorescence was enhanced by the addition of carboxymethylcellulose solution and measured at 455 nm after excitation at 339 nm. The method was successfully applied to the analysis of CLP in tablets and biological fluids. In both methods, interference likely to be introduced from co-formulated, co-administered, or chemically related drugs was studied. The results were statistically compared with those obtained by reference methods and were found to be in good agreement.

First derivative synchronous fluorescence spectroscopy for the simultaneous determination of sulpiride and mebeverine hydrochloride in their combined tablets and application to real human plasma.

A rapid, simple and highly sensitive first derivative synchronous fluorometric method has been developed for the simultaneous analysis of binary mixture of sulpiride (SUL) and mebeverine hydrochloride (MEB). The method is based upon measurement of the synchronous fluorescence intensity of these drugs at ∆λ = 100 nm in water. The different experimental parameters affecting the fluorescence of the two drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.05-1 µg/mL and 0.2-3.2 µg/mL for SUL and MEB respectively with lower detection limits (LOD) of 0.006 and 0.01 µg/mL and quantification limits (LOQ) of 0.0.02 and 0.05 µg/mL for SUL and MEB, respectively. The proposed method was successfully applied for the determination of the two compounds in synthetic mixtures and in commercial tablets. The high sensitivity attained by the proposed method allowed the determination of both of SUL and MEB metabolite (veratic acid) in real human plasma samples applying second derivative synchronous fluorometric technique. The mean% recoveries (n = 3) for both MEB metabolite (veratic acid) and SUL were 99.82 ± 2.53 and 98.84 ± 6.20 for spiked human plasma respectively, while for real human plasma, the mean% recoveries (n = 3) were 91.49 ± 4.25 and 91.36 ± 8.46 respectively.

Kinetic determination of ribavirin in drug formulations.

Two simple and sensitive kinetic methods were developed for the determination of ribavirin in bulk and in its pharmaceutical preparations using alkaline potassium permanganate as an oxidizing agent. The methods are based upon a kinetic investigation of the oxidation reaction of the drug at room temperature for fixed times of 20 and 30 minutes. In the first method, the absorbance of the colored manganate ion was measured at 610 nm, while in second method the reduction in the absorbance of permanganate was measured at 525 nm. The absorbance concentration plots were linear over the range of 3-15 µg/ml with detection limits of 0.028 µg/ml in the first method and 0.229 µg/ml for the second method. The proposed methods were applied successfully for the determination of the drug in its pharmaceutical formulations, the percentage recoveries were 100.15 ± 1.34, 100.06 ± 0.86 in the first method, and 99.60 ± 0.54, 100.43 ± 0.82 in the second method. The results obtained were compared statistically with those obtained by the official method and showed no significant differences regarding accuracy and precision.

Spectrophotometric determination of nizatidine and ranitidine through charge transfer complex formation.

Two Spectrophotometric procedures are presented for the determination of two commonly used H2-receptor antagonists, nizatidine (I) and ranitidine hydrochloride (II). The methods are based mainly on charge transfer complexation reaction of these drugs with either p-chloranilic acid (rho-CA) or 2, 3 dichloro-5, 6-dicyanoquinone (DDQ). The produced colored products are quantified spectrophotometrically at 515 and 467 nm in chloranilic acid and DDQ methods, respectively. The molar ratios for the reaction products and the optimum assay conditions were studied. The methods determine the cited drugs in concentration ranges of 20-200 and 20-160 microg/mL for nizatidine and ranges of 20-240 and 20-140 microg/mL for ranitidine with chloranilic acid and DDQ methods, respectively. A more detailed investigation of the complexes formed was made with respect to their composition, association constant, molar absorptivity and free energy change. The proposed procedures were successfully utilized in the determination of the drugs in pharmaceutical preparations. The standard addition method was applied by adding nizatidine and ranitidine to the previously analyzed tablets or capsules. The recovery of each drug was calculated by comparing the concentration obtained from the spiked mixtures with those of the pure drug. The results of analysis of commercial tablets and the recovery study (standard addition method) of the cited drugs suggested that there is no interference from any excipients, which are present in tablets or capsules. Statistical comparison of the results was performed with regard to accuracy and precision using student's t-test and F-ratio at 95% confidence level. There is no significant difference between the reported and proposed methods with regard to accuracy and precision.

Spectrophotometric determination of fenoterol hydrobromide in pure form and dosage forms.

A sensitive and rapid spectrophotometric procedure has been investigated for the determination of fenoterol either per se or in pharmaceutical preparations. The proposed procedure is based on the reaction between the drug and 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) at pH 7.2, using borate buffer, to produce a yellow adduct. The latter has maximum absorbance at 400 nm and obeys Beer's law within the concentration range 5-30 microg/ml. Regression analysis of the calibration data showed a good correlation coefficient (r=0.9996) with minimum detection limit of 0.24 microg/ml (6.2 x 10(-8) M). The proposed procedure has been successfully applied to the determination of this drug in its tablets and in syrup, the mean percent recoveries were 97.45+/-0.59 and 98.7+/-0.64%, respectively. The results obtained are in good agreement with those given using a reference method. The pharmaceutical additives other than active ingredient did not interfere. A proposal of the reaction pathway has been postulated.

Application of difference spectroscopy to the determination of some pharmaceutically important nitro compounds.

A simple and selective spectrophotometric method for the determination of some pharmaceutically important nitro compounds has been developed. The suggested method depends upon the spectral changes induced by reduction using either Zn/HCl or Zn/NH4Cl. The different experimental parameters were studied and incorporated into the procedure. The mean percentage recovery ranged from 99 to 101. The proposed method was applied to the determination of the studied compounds in dosage forms, and the results obtained were compared favourably with those given with the compendial ones.

Uptake of ferrous iron histidinate, a promoter of lipid peroxidation, by Ehrlich ascites tumor cells.

The kinetics of the uptake of Fe(II)-histidinate, a known promoter of lipid peroxidation, into Ehrlich ascites tumor (EAT) cells and the intracellular binding of iron were studied in vitro. EAT cells (27.10(6)/ml) were incubated in Hanks' balanced salts solution at 37 degrees C for various time intervals in the presence of FeSO4 (1 mM) and L-histidine (10 mM). Total iron was determined by the 1,10-phenanthroline/ascorbate method and ferric iron by reaction with 5-sulfosalicylic acid; the difference was ascribed to ferrous iron. Total iron decreased rapidly in the medium (242 nmol within the first 10 min), and a corresponding increase of total iron (saturation value 376 nmol after 60 min) was determined within the cells, after the cellular proteins had been solubilized with 6 M urea. In the absence of EAT cells, Fe(II)-histidinate was readily oxidized to Fe(III)-histidinate by oxygen, but this reaction was strongly retarded by the tumor cells. The uptake of iron histidinate occurred in the oxidized state, while an uptake of ferrous iron could not be proven unambiguously. When EAT cells were saturated with iron, it was found that 93% of intracellular iron was bound to water-insoluble proteins and 7% was associated with soluble proteins, while no unbound iron was detectable by the method used. It was concluded that, despite the high uptake of total iron, only a very small portion of the intracellular iron was available as a redox catalyst for lipid peroxidation.