Spectrophotometric determination of Valsartan in pure form and in its pharmaceutical preparations

An easy, rapid and economical spectrophotometric method for determination of Valsartan (Val), by reaction with 4-chloro-7-nitrobenzofurazan (NBD-Cl) as reagent in an alkaline interemediate. This method is based on the forming of product between (Val) and the chromogenic reagent (NBD-Cl), to produce a brown color at (pH 11.9) and λmax. 470 nm. Beer’s Law is obeyed at the concentrations range of (0.4-14.8 µg/ml), with molar absorptivity of (1.05×104 L/mol.cm) and correlation coefficient 0.9827, The limit of detection was 0.557 µg/ml. The suggested method was prosperity implement to the determination of (Val) in pure form and in its pharmaceutical formulations (tablets).

UV-Vis Spectrophotometric Determination of Selected Heavy Metals (Pb, Cr, Cd and As) in Environmental, Water and Biological Samples with Synthesized Glutaraldehyde Phenyl Hydrazone as the Chromogenic Reagent

A simple, sensitive, selective, and non-extractive UV-Vis spectrophotometric method for the determination of cadmium, lead, chromium, and arsenic in biological, soil and water samples using synthesized and characterized phenyl hydrazone; glutaraldehydephenyl hydrazone (GPH) as the chromogenic reagent was developed. GPH was synthesized as new chromogenic analytical reagents for the direct UV-Vis spectrophotometric determination of the selected metals of interest in a slightly acidic pH of 6.5-7.5 and 20 % dimethylformamide (DMF) solution to give stable coloured metal-ligand complexes. The reactions were instantaneous; the wavelengths of maximum absorptions were followed spectrophotometrically and noted. The reagent GPH revealed a wavelength of maximum absorption between 360.0 (Cr) to 395.0 nm for (Pb and As) at a working pH of 6.5 to 7.5 room temperature (37 °C). The reagent GPH had a molar absorptivity (L mol-1 cm-1) ranging from 2.213×104 (Pb) to 2.460×104 (As), a mole ratio of metal to ligand of 2:1, the detection limit (µg/g) ranging from 0.3432 (As) to 0.5250 (Pb) and the metal-ligand complex was stable for 0-48 hours. The reagents had a Beer’s law validity range (mg L-1) of 0.001 to 100. The Sandell’s sensitivities (µg/cm2) ranged from 0000409 (As) to 0.00499 (Pb) for APDH and 0.00406 (As) to 0.00452 (Pb) respectively. Large excess of cations and anions as possible interferences up to 15 folds were studied and do not interfere with the determination of the selected metals of interest. The developed method is highly selective for Cd, Pb, and Cr and As and was successfully used for the determination for the said elements in soil, water, and biological samples. The results of the developed methods were comparable with AAS and were found to be in good agreement. The method had very high precision and very good accuracy.

Experimental and Computational Evaluation of Chloranilic Acid as an Universal Chromogenic Reagent for the Development of a Novel 96-Microwell Spectrophotometric Assay for Tyrosine Kinase Inhibitors

The tyrosine kinase inhibitors (TKIs) are chemotherapeutic drugs used for the targeted therapy of various types of cancer. This work discusses the experimental and computational evaluation of chloranilic acid (CLA) as a universal chromogenic reagent for developing a novel 96-microwell spectrophotometric assay (MW-SPA) for TKIs. The reaction resulted in an instantaneous formation of intensely purple colored products with TKIs. Spectrophotometric results confirmed that the reactions proceeded via the formation of charge-transfer complexes (CTCs). The physical parameters were determined for the CTCs of all TKIs. Computational calculations and molecular modelling for the CTCs were conducted, and the site(s) of interaction on each TKI molecule were determined. Under the optimized conditions, Beer’s law correlating the absorbances of the CTCs with the concentrations of TKIs were obeyed in the range of 10–500 µg/well with good correlation coefficients (0.9993–0.9998). The proposed MW-SPA fully validated and successfully applied for the determination of all TKIs in their bulk forms and pharmaceutical formulations (tablets). The proposed MW-SPA is the first assay that can analyze all the TKIs on a single assay system without modifications in the detection wavelength. The advantages of the proposed MW-SPA are simple, economic and, more importantly, have high throughput.

Determination of Cysteine by Discoloration Spectrophotometry using Copper(II)-Bis-Cyclohexanone Oxalydihydrazone

In the alkaline medium of pH=9.18, Cu2+ can be reduced to Cu+ by the sulfhydryl (-SH) of cysteine, and it result in the decrease the amount of Cu2+ in the system. The decrement of Cu2+ is directly proportional to the addition of cysteine, then using bis-cyclohexanone oxalyldihydrazone (BCO) as chromogenic reagent for Cu2+ to determinate the content of cysteine indirectly by discoloration spectrophotometry. A new method for the determination of cysteine by discoloration spectrophotometry using Copper(II)-BCO has been established. The influencing factors of the determination of cysteine is investigated. The results show that the maximum absorption wavelength of chromogenic system was 602 nm, in the range of 0.008000~0.06800 mg/mL, the linear relationship between the decrease of absorbance and the mass concentration of methimazol is A=0.2162+2.4824C (mg/mL), and the linear correlation coefficient is r=0.9959. The method has been applied to the determination of cysteine in food, and the results are basically consistent with those determined by pharmacopoeial method.

Spectrophotometric Determination of Cu(II) in Analytical Sample Using a New Chromogenic Reagent (HPEDN)

The sensitive, accurate and rapid spectrophotometric method that can be used for determination of Cu(II) in the analytical samples using a new chromogenic reagent azo-Schiff base 1-((4-(1-(2-hydroxyphenylimino)ethyl)-phenyl)diazenyl) naphthalene-2-ol (HPEDN). The synthesized new (azo-Schiff base) ligand was complexed with copper(II) and characterized using UV/Vis spectroscopy, IR spectra, 1H-NMR, 13CN-MR spectra, Molar electrical connectivity, and measuring of their melting points. Then obtained complex showed a brown color with maximum absorption at λmax = 500 nm at pH = 9. Beer’s law is obeyed in the concentration in the range of 1.7 to 5.4 μg/mL. The molar absorption and Sandell’s sensitivity values of Cu(II) complex were found to be 0.5038 × 104 L mol–1 cm–1 and 0.0039 μg cm–2, respectively. Structure of the prepared complex was investigated by using the continuous variation, mole ratio method and slope analysis method. The obtained results showed that the complex has (1:2) (M:L) molar ratio and these results showed that this method were more sensitive, more precise and accuracy through the calculation of (Re, Erel, R.S.D)%. The most important interferences were due to, Co2+, Cd2+, Zn2+, Ni2+, Mn2+, Pd2+, Fe3+ and these were studied, and suitable masking agents were used. This method was applied for the determination of Cu(II) in alloy. The obtained results were compared with flame atomic absorption spectrometry method and these results were in a good agreement in these two cases.