Non-extractive spectrophotometric determination of valsartan in pure form and in pharmaceutical products by ion-pair complex formation with bromophenol blue and methyl red

Two simple, rapid, green non extractive spectrophotometric methods are described for the estimation of valsartan in tablet dosage form. The determination is based on the ion-pair formation using the dyes, bromophenol blue (BPB) and methyl red (MR). Valsartan forms ion-pair complex selectively with the dyes, as indicated by the formation of a coloured complex with BPB at pH 5.5 with λmax at 424 nm and MR at pH 4.3 with λmax at 494 nm. For both methods, optimal spectrophotometric conditions were established. The linear relationship was found between absorbance at λmax and concentration of drug in the range 8–24 µg/mL for BPB and 4–20 µg/mL for MR. Regression analysis of Beer’s law plot at 424 nm yielded the regression equation, y = 0.0102x + 01636 (BPB) and at 494 nm y = 0.0222x – 0.0063 (MR). High values of correlations coefficient (R2 = 0.9988 (BPB) and R2 = 0.9991 (MR)) and small values of intercept validated the linearity of calibration curve and obedience to Beer’s law. The LOD and LOQ values were calculated to be 1.03 µg/mL and 3.43 µg/mL respectively (BPB) and 0.68 µg/mL and 2.26 µg/mL respectively (MR). Intra-day and inter-day accuracy and precision, robustness were in acceptable limits. The proposed methods were applied for the quantification of valsartan in tablets pertaining to three commercial formulations. Analytical eco-scale for greenness assessment of the proposed spectrophotometric methods showed that both methods corresponds to excellent green analysis with a score of 89.

Assessment of Cymoxanil in Soil, Water and Vegetable Samples

The present work describes a newly developed method for the spectrophotometric determination of cymoxanil in soil, water and vegetable samples. The detection of the target chemical substance is based on the reaction of cyanide released from the hydrolysed product of cymoxanil with potassium iodide-potassium iodate to form a blue-coloured complex in the presence of starch solution. This complex is water-soluble and shows maximum absorbance at 580 nm. For this complex, Beer's law is obeyed over the concentration range of 2-50 μg mL−1 with molar absorptivity 1.2×105 L mol-1cm-1 and Sandell’s sensitivity 1.0×10-3 µg cm-2. The reproducibility was assessed by carrying out seven days replicate analysis of a solution containing 10 µgmL-1 of cymoxanil in a final solution of a volume of 10 mL. The standard deviation and relative standard deviation for the absorbance value were found to be ± 2.9×10-3 and 1.6% respectively. The proposed method is free from the interference of other toxicants. The analytical parameters were optimized and the method was applied to the determination of cymoxanil in water, soil, and vegetable samples.

The kinetics and mechanism of the ligand substitution reaction of aquapentacyanoruthenate(II) with d-penicillamine in aqueous medium

The kinetics of the formation of the light orange–coloured complex [Ru(CN)5D-PA]3− are studied spectrophotometrically through substitution of a coordinated H2O molecule in aquapentacyanoruthenate(II) [Ru(CN)5OH2]3− by interaction with D-penicillamine [D-PA] in aqueous medium at 490 nm (λmax of [Ru(CN)5D-PA]3−). The reaction is monitored under pseudo-first-order conditions, taking [D-PA] in excess over [Ru(CN)5OH23−]. The effects of various reaction parameters on the rate of the reaction are investigated. Experimental observations reveal that the variation in [D-PA] obeyed the first-order rate law while it is found to be invariant with [Ru(CN)5OH23−] in the whole experimental range. With ionic strength variation, as the reaction advances a decrease in the reaction rate is noticed. The product stoichiometry is assigned as 1:1. The ease of substitution at an H2O molecule in [Ru(CN)5OH23−] is considered on the basis of the electronic effect generated through interactions of the M–OH2 bond. A provisional mechanism based on the calculated results is proposed based on the slowest step of the reaction.

SPECTROSCOPIC AND VOLUMETRIC TECHNIQUES FOR THE ESTIMATION OF IVABRADINE IMPURITY 3,3'-(PROPANE-1,3-DIYL)BIS(7,8-DIMETHOXY-1,3,4,5-TETRAHYDRO-2H-BENZO[D]AZEPIN-2-ONE)

Objective: Two simple and sensitive techniques - one spectrophotometric and one titrimetric- have been developed for the determination of 3,3'-(propane-1,3-diyl)bis(7,8-dimethoxy-1,3,4,5-tetrahydro-2H-benzo[d]azepin-2-one) commonly known as ivabradine impurity-9 (IVA-9). Methods: The spectrophotometric method is based on the oxidation of drug impurity by excess cerium (IV) sulphate in acidic medium and the subsequent reaction of the remaining Ce(IV) with a known amount of ferrous ammonium sulphate. The resultant ferric ion is then made to react with thiocyanate in acid medium to form a brown coloured complex which is analyzed spectrophotometrically against the reagent blank. In the volumetric method, the un-reacted Ce(IV) is titrated against standard ferrous ammonium sulphate to estimate the quantity of IVA-9. Results: The colored complex showed an absorption maximum at 479 nm when measured spectrophotometrically. The stated methods are validated statistically using the International Council for Harmonization guidelines-ICH Q2(R1) for precision and accuracy. The method showed a linear response from 0.5 to 100µg/ml with a correlation coefficient of 0.9985 Conclusion : No estimation techniques have been reported to date for the determination of this molecule. The proposed techniques may be used for the routine quantification in its pure form and also in presence of its parent drug molecule Ivabradine.

Development and Optimization of Green Method for Antihistamine Using Ecofriendly Reagent in Pure and Pharmaceutical Formulations by Microwave Assisted Spectrophotometry

Synthetic substances and solvents utilized in investigation of drugs crumble the earth as well as human health. So attempts should be made to minimize or eliminate the utilization of obnoxious chemicals and solvents. The objective of study is to develop the green spectroscopic method using new ecofriendly chromogenic reagent for the evaluation of antihistamine i.e. desloratadine in pure and commercial dosage forms. Both heating systems (conventional and microwave assisted procedures) are used for the development of color. The method is based on formation of stable blue coloured complex with ammonium molybdate in the presence of acid having λmax at 732nm respectively. All the reaction conditions and different statistic parameters for the proposed methods have been studied. The method is found to be rapid, precise and accurate and can be successfully used for the determination of antihistamines in bulk and commercial tablet formulations.

Simultaneous Quantification of Vitamin A and E in Pharmaceutical Formulations and fruit Samples Using Fe(II)-1-Nitroso-2-Napthol Complex

A rapid and sensitive spectrophotometric method for the determination of vitamin A and vitamin E using Fe(II)-1-nitroso-2-napthol detection system is reported. The in situ reduced Fe(II) formed green coloured complex with 1-nitroso-2-napthol which gives an absorption maxima at 708nm. Beer’s law was obeyed in the range 4.0-14.0μg/mL for vitamin A and 4.0-24.0μg/mL for vitamin E with relative standard deviation 1.7% for vitamin A and 2.2% for vitamin E. The molar absorptivity was found to be 1.3×104 L mol-1 cm-1 for vitamin A and 2.5×104 L mol-1 cm-1 for vitamin E with the co-relation coefficients 0.996 and 0.935 for vitamin A and vitamin E respectively. Optimization of various factors was done to get the maximum absorption value. The proposed method is utilized satisfactorily for pharmaceuticals, milk sample,fruit sample and different liquid samples of vitamin A and vitamin E by pre treatment of samples.

DEVELOPMENT AND VALIDATION OF A U.V SPECTROPHOTOMETRIC METHOD FOR ESTIMATION OF CISPLATIN IN PHARMACEUTICAL FORMULATIONS

A simple, accurate, specific and reproducible colorimetric method was developed for cisplatin in pharmaceutical formulations. The analytical method was based on the formation of a stable, light blue coloured complex upon reaction between cisplatin and ortho-phenylene diamine at pH 7.4. The λmax of the solution was obtained at 702 nm in phosphate buffer saline 7.4. Optimized OPDA concentration and complexation time for the procedure were 1.2 mg/mL and 10 minutes respectively. Developed method in PBS 7.4 was found to be linear in the range of 1-10μg/mL with a regression coefficient of 0.999 and exhibiting line equation y = 0.102x – 0.004. Recovery of marketed cisplatin injection was found to be in the range of 98.8-99.1%. Drug content for the developed nanoformulation was in the range of 98-101% indicating no interference of excipients. These results illustrate that the developed method could be successfully employed for quantitative estimation of cisplatin in pharmaceutical formulations.

Spectrophotometric Determination of Phosphate in Sugarcane Juice, Fertilizer, Detergent and Water Samples by Molybdenum Blue Method

A simple and sensitive spectrophotometric method has been developed for the determination of phosphate in mg per liter (parts per million) concentration range in sugarcane juice, water, fertilizer and detergent samples. The amount of phosphate is determined by molybdenum blue phosphorus method in conjugation with UV-visible spectrophotometer. This method is based on the formation of phosphomolybdate complex with the added molybdate followed by the reduction of the complex with hydrazine hydrate in aqueous sulphuric acid medium. The system obeys Lambert-Beer’s law at 840 nm in the concentration range 0.1-11 ppm. The colour intensity of the reduced phosphomolybdate solution is found to be proportional to the amount of phosphate present in sugarcane juice, water, fertilizer and detergent samples. The reaction conditions as well as the various experimental parameters affecting the development and stability of the coloured complex were carefully investigated and optimized for the quantitative determination of phosphate present in various samples. The optimized concentrations of various reagents used are 0.20N sulphuric acid, 0.02M hydrazine hydrate and 0.20% ammonium molybdate. The effect of time on the formation of phosphomolybdenum blue complex and addition of the order of the reagents was also studied. Scientific World, Vol. 11, No. 11, July 2013, page 58-62DOI: http://dx.doi.org/10.3126/sw.v11i11.9139

Solvent Extraction And Spectrophotomteric Determination Of Cu(Ii) With Dicyclohexyl - 18- Crown-6

Liquid-Liquid Extraction of Cu(II) ion in aqueous solution by dicyclohexyl-18-crown-6 as extractant in dichloroethane was studied .The extraction efficiency was investigated by a spectrophometric method. The reagent form a coloured complex which has been a quantitatively extracted at pH 6.3. The method obeys Beer`s law over range from (2.5-22.5) ppm with the correlation coefficient of 0.9989. The molar absorptivity the stoichiometry of extracted complex is found to be 1:2. the proposed method is very sensitive and selective.

Development of Method for Extractive Spectrophotometric Determination of Fe(III) with 2-Hydroxy-1-Naphthalene Carboxaldehyde Phenyl Hydrazone as an Analytical Reagent

A spectrophotometric method has been developed for the determination of Fe(III) using 2-Hydroxy-1-Naphthalene carboxaldehyde phenyl hydrazone as an extractive reagent. The reagent forms a coloured complex, which has been quantitatively extracted into ethyl acetate at pH 6. The method obeys Beer’s law over arrange from 1 to 7 ppm. The Molar absorptivity and Sandell’s sensitivity were 0.31 × 104 L mol-1cm-1 and 0.13 μg cm-2 respectively. The proposed method is very sensitive and selective. The method has been successfully applied to synthetic and commercial samples.