Determination of lignocaine and amprolium in pharmaceutical formulations using AAS.

The ion-associate complexes of lignocaine hydrochloride (Lig.Cl) with ammonium reineckate (Rk) or sodium cobaltithiocyanate, and that of amprolium hydrochloride (Amp.Cl) with ammonium reineckate, have been prepared. The precipitated ion-associates were subjected to elemental analyses, infrared and nuclear magnetic resonance spectroscopy and determination of the metal content for elucidation of their structures. The solubilities of the solid ion-associate complexes have been studied and their solubility products were determined at different temperatures at the optimum pH for their quantitative precipitation. The thermodynamic parameters DeltaH, DeltaG and DeltaS for the dissolution of the ion-associate complexes were calculated. These ion-associate complexes have been used for the quantitative determination of the above mentioned drugs by precipitating them with an excess of the inorganic metal complex ions and determining the excess metal complex ions using atomic absorption spectrometry. The method was applied for the determination of the above drugs in pure solution and pharmaceutical preparations. 0.135-135.4 and 0.158-157.6 mg of lignocaine and amprolium, respectively, can be determined with mean relative standard deviations (R.S.D.) 0.92-1.20% and recovery values of 99.18+/-0.48 to 100.12+/-0.34% indicating high precision and accuracy.

IR, 1H NMR, mass, XRD and TGA/DTA investigations on the ciprofloxacin/iodine charge-transfer complex.

The charge-transfer complex (CTC) of ciprofloxacin drug (CIP) as a donor with iodine (I(2)) as a sigma acceptor has been studied spectrophotometrically in CHCl(3). At maximum absorption bands, the stoichiometry of CIP:iodine system was found to be 1:1 ratio according to molar ratio method. The essential spectroscopic data like formation constant (K(CT)), molar extinction coefficient (ɛ(CT)), standard free energy (ΔG°), oscillator strength (f), transition dipole moment (µ), resonance energy (R(N)) and ionization potential (I(D)) were estimated. The spectroscopic techniques such as IR, (1)H NMR, mass and UV-vis spectra and elemental analyses (CHN) as well as TG-DTG and DTA investigations were used to characterize the chelating behavior of CIP/iodine charge-transfer complex. The iodine CT interaction was associated with a presence of intermolecular hydrogen bond. The X-ray investigation was carried out to investigate the iodine doping in the synthetic CT complex.

Spectrophotometric determination of sildenafil citrate in pure form and in pharmaceutical formulation using some chromotropic acid azo dyes.

Two simple and highly sensitive spectrophotometric methods were developed for the quantitative determination of the drug sildenafil citrate (SC), Viagra, in pure form and in pharmaceutical formulations, through ion-associate formation reactions (method A) with mono-chromotropic acid azo dyes, chromotrope 2B (I) and chromotrope 2R (II) and ion-pair reactions (method B) with bi-chromotropic acid azo dyes, 3-phenylazo-6-o-carboxyphenylazo-chromotropic acid (III), bis-3,6-(o-hydroxyphenylazo)-chromotropic acid (IV), bis-3,6-(p-N,N-dimethylphenylazo)-chromotropic acid (V) and 3-phenylazo-6-o-hydroxyphenylazo-chromotorpic acid (VI). The reaction products, extractable in methylene chloride, were quantitatively measured at 540, 520, 540, 570, 600 and 575 nm using reagents, I-VI, respectively. The reaction conditions were studied and optimized. Beer's plots were linear in the concentration ranges 3.3-87.0, 3.3-96.0, 5.0-115.0, 2.5-125.0, 8.3-166.7 and 0.8-15.0 microg mL(-1) with corresponding molar absorptivities 1.02 x 10(4), 8.34 x 10(3), 6.86 x 10(3), 5.42 x 10(3), 3.35 x 10(3) and 2.32 x 10(4)Lmol(-1) cm(-1) using reagents I-VI, respectively. The limits of detection and Sandell's sensitivities were calculated. The methods were successfully applied to the analysis of commercial tablets (Vigoran) and the recovery study reveals that there is no interference from the common excipients that are present in tablets. Statistical comparison of the results was performed with regard to accuracy and precision using Student's t- and F-tests at 95% confidence level. There is no significant difference between the reported and proposed methods with regard to accuracy and precision.

Spectrophotometric Determination of Diazepam in Pure form, Tablets and Ampoules.

The interaction of diazepam with picric acid (I), 3,5-dinitrobenzoic acid (II) and 2,4-dinitrobenzoic acid (III) was found to be useful for its spectrophotometric determination. The quantitation was carried out at 475, 500, and 500 nm for the reaction with (I), (II) and (III), respectively. The effect of several variables on the coloring process was studied. The proposed methods have been applied successfully for the determination of diazepam in pure samples and in its pharmaceutical preparations with good accuracy and precision. The results were compared to those obtained by the pharmacopoeial methods. The linear ranges for obedience of Beer's law are up to 85.6, 180.2, and 128.6 µg/ml, Ringbom ranges are 10.0-79.0, 15.2-177.8, 17.0-83.0 µg/ml, and RSD 0.048, 0.028, and 0.026% for reaction of diazepam with I, II, and III, respectively.