Microanalytical determination of calcium, phosphate, and arsenate including kinetics of formation of molybdenum blue from reduction of molybdoarsenic acid by ferrous ammonium sulphate

1987 ◽  
Vol 65 (6) ◽  
pp. 1313-1315 ◽  
Author(s):  
U. S. Rat ◽  
T. S. B. Narasaraju
Keyword(s):  
Calcium Phosphate ◽  
Ammonium Sulphate ◽  
Ferrous Ammonium Sulphate ◽  
Molybdenum Blue ◽  
Spectrophotometric Methods ◽  
Rate Determining Step ◽  
Kinetics Of Formation ◽  
Ferrous Ammonium ◽  
Kinetics Of

A method for the microdetermination of calcium, phosphate, and arsenate in mixtures of the three has been developed. In an aliquot of the mixture calcium was determined complexometrically using EDTA. Phosphate and arsenate were determined in second and third aliquots, respectively, using spectrophotometric methods. The interference of arsenate in the determination of phosphate was avoided by masking arsenate with thiosulphate. The kinetics of formation of molybdenum blue from molybdoarsenic acid by reduction with ferrous ammonium sulphate was also studied. The rate-determining step was found to be the reduction of molybdoarsenic acid with iron(II); the reaction was first order in iron(II) and arsenate over the concentration ranges studied. Values found for the enthalpy, entropy, and free energy of activation were 22, 0.05, and 7.5 kcal, respectively.

scholarly journals 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)

2019 ◽  
pp. 216-218
Author(s):  
S. ANIL KUMAR ◽  
B. L. BHASKAR
Keyword(s):  
Ammonium Sulphate ◽  
Parent Drug ◽  
Ferrous Ammonium Sulphate ◽  
Subsequent Reaction ◽  
Drug Molecule ◽  
Reagent Blank ◽  
Colored Complex ◽  
Coloured Complex ◽  
Ferrous Ammonium

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.

The retroaldol reaction of 3-methyl-2-butenal

1983 ◽  
Vol 61 (1) ◽  
pp. 171-178 ◽  
Author(s):  
J. Peter Guthrie ◽  
Brian A. Dawson
Keyword(s):  
Sodium Hydroxide ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Aqueous Sodium Hydroxide ◽  
Initial Increase ◽  
Aqueous Sodium ◽  
Rate Determining Step ◽  
Kinetics Of

In aqueous sodium hydroxide solutions at 25 °C, 3-methyl-2-butenal, 1c, undergoes retroaldol cleavage to acetone and acetaldehyde. The kinetics of the retroaldol reaction were followed spectrophotometrically at 242 nm and showed simple first order behavior. When 3-methyl-3-hydroxybutanal, 2c, was added to aqueous sodium hydroxide solutions at 25 °C, there was an initial increase in absorbance at 242 nm, attributed to formation of 1c, followed by a 20-fold slower decrease; the rate of the slow decrease matches the rate of disappearance of 1c under the same conditions. Analysis of the kinetics allows determination of the three rate constants needed to describe the system: khyd = 0.00342; kdehyd = 0.00832; kretro = 0.0564; all M−1 s−1. The equilibrium constant for enone hydration is 0.41. Rate constants for the analogous reactions for acrolein and crotonaldehyde could be obtained from the literature. There is a reasonable rate–equilibrium correlation for the retroaldol step. For the enone hydration step, rate and equilibrium constants respond differently to replacement of hydrogen by methyl. It is proposed that this results from release of strain after the rate-determining step by rotation about a single bond; this decrease in strain is reflected in the equilibrium constant but not in the rate constant.

Modifications of spectrophotometric methods for total phosphorus determination in meat samples

2009 ◽  
Vol 63 (1) ◽  
Author(s):  
Aneta Jastrzębska
Keyword(s):  
Total Phosphorus ◽  
Reducing Agents ◽  
Statistical Parameters ◽  
Molybdenum Blue ◽  
Spectrophotometric Methods ◽  
Hydrazine Sulphate ◽  
Meat Samples ◽  
Blue Reaction ◽  
Better Than

AbstractSpectrophotometric determination of total phosphorus in meat samples was modified using the molybdenum blue reaction with the following reducing agents: ascorbic acid (AA), hydrazine sulphate (HS), and mixture of hydroquinone and hydrazine sulphate (HHS). Proposed methods were validated by evaluation of statistical parameters such as: linearity, sensitivity, limits of detection (DL) and quantification (QL), precision, and accuracy, against the standard and malachite green (MG) modified procedures and by applying food certified materials. The values of within-day and between-days precision in meat samples for all tested reducing agents were better than 3.4 % and 4.2 %, respectively. The recoveries for CRMs analyses were between 92 % and 102.3 %. Obtained results suggest usefulness of the hydroquinone and hydrazine sulphate mixture in the determination of phosphorus ions.

scholarly journals Examination of steam gasification of coal with physically mixed catalysts

2019 ◽  
Vol 21 (4) ◽  
pp. 51-57 ◽  
Author(s):  
Katarzyna Śpiewak ◽  
Grzegorz Czerski ◽  
Agnieszka Sopata
Keyword(s):  
Coal Gasification ◽  
Steam Gasification ◽  
Conversion Degree ◽  
Process Time ◽  
Gasification Process ◽  
Kinetics Of Formation ◽  
Short Time ◽  
Kinetics Of ◽  
Positive Effect

Abstract The aim of this study was to analyse the steam gasification process of ‘Janina’ coal with and without Na-, K- and Ca-catalysts. The catalysts were physically mixed with the coal due to the simplicity of this method, short time of execution and certainty that the amount of catalyst is exactly as the adopted one. The isothermal measurements were performed at 800, 900 and 950°C and a pressure of 1 MPa using thermovolumetric method. The obtained results enabled assessment of the effect of analysed catalysts on the process at various temperatures by determination of: i) carbon conversion degree; ii) yield and composition of the resulting gas; and iii) kinetics of formation reactions of main gas components – CO and H2. The addition of catalysts, as well as an increase in operating temperature, had a positive effect on the coal gasification process – reactions rates increased, and the process time was reduced.

scholarly journals Use of ceric ammonium sulphate and two dyes, methyl orange and indigo carmine, in the determination of lansoprazole in pharmaceuticals

2007 ◽  
Vol 57 (2) ◽  
pp. 211-220 ◽  
Author(s):  
Kanakapura Basavaiah ◽  
Veeraiah Ramakrishna ◽  
Urdigere Kumar
Keyword(s):  
Methyl Orange ◽  
Ammonium Sulphate ◽  
Indigo Carmine ◽  
Correlation Coefficients ◽  
Standard Addition ◽  
Fixed Amount ◽  
Spectrophotometric Methods ◽  
Relative Standard ◽  
Bulk Drug

Use of ceric ammonium sulphate and two dyes, methyl orange and indigo carmine, in the determination of lansoprazole in pharmaceuticalsTwo spectrophotometric methods are proposed for the assay of lansoprazole (LPZ) in bulk drug and in dosage forms using ceric ammonium sulphate (CAS) and two dyes, methyl orange and indigo carmine, as reagents. The methods involve addition of a known excess of CAS to LPZ in acid medium, followed by determination of residual CAS by reacting with a fixed amount of either methyl orange, measuring the absorbance at 520 nm (method A), or indigo carmine, measuring the absorbance at 610 nm (method B). In both methods, the amount of CAS reacted corresponds to the amount of LPZ and the measured absorbance was found to increase linearly with the concentration of LPZ, which is corroborated by the correlation coefficients of 0.9979 and 0.9954 for methods A and B, respectively. The systems obey Beer's law for 0.5-7.0 μg mL-1and 0.25-3.0 μg mL-1for methods A and B, respectively. The apparent molar absorptivities were calculated to be 3.0 x 104and 4.4 x 104L mol-1cm-1for methods A and B, respectively. The limits of detection (LOD) and quantification (LOQ) were calculated to be 0.08 and 0.25 μg mL-1for method A, and 0.09 and 0.27 μg mLs-1for method B, respectively. The intra-day and inter-day precision and accuracy of the methods were evaluated according to the current ICH guidelines. Both methods were of comparable accuracy (er≤ 2 %). Also, both methods are equally precise as shown by the relative standard deviation values < 1.5%. No interference was observed from common pharmaceutical adjuvants. The accuracy of the methods was further ascertained by performing recovery studies using the standard addition method. The methods were successfully applied to the assay of LPZ in capsule preparations and the results were statistically compared with those of the literature UV-spectrophotometric method by applying Student'st-test andF-test.

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