Determination of the visible spectra of electrode reaction products in strongly absorbing media by diffusion-controlled chronoabsorptometry

1996 ◽  
Vol 74 (7) ◽  
pp. 1403-1408 ◽  
Author(s):  
David H. Jones ◽  
A. Scott Hinman
Keyword(s):  
Thin Layer ◽  
Electrode Reaction ◽  
Molar Absorptivity ◽  
Bulk Solution ◽  
Reaction Products ◽  
Optical Absorbance ◽  
Current Path ◽  
Diffusion Controlled ◽  
Visible Spectra

Chronoabsorptometry under diffusion-controlled conditions has been applied to determination of the difference in molar absorptivity between electrode reaction products and reactants. The technique allows complete determination of the ultraviolet–visible spectra of reaction products that are stable on the time scale of a few hundred milliseconds. The technique was implemented with a reflectance cell that employs quartz light pipes to minimize optical absorbance of the bulk solution without obstructing the current path between counter and working electrodes. The spectrum of one-electron oxidized chloro-(5,10,15,20-tetraphenylporphinato)Fe(III) is determined with the new technique and compared with that obtained by conventional thin-layer spectroelectrochemistry. Key words: spectroelectrochemistry, chronoabsorptometry, thin-layer spectroelectrochemistry.

Molar Absorptivity Values for Aflatoxins and Justification for Their Use as Criteria of Purity of Analytical Standards

1970 ◽  
Vol 53 (1) ◽  
pp. 96-101 ◽  
Author(s):  
J V Rodricks ◽  
L Stoloff ◽  
W A Pons ◽  
J A Robertson ◽  
L A Goldblatt
Keyword(s):  
Thin Layer ◽  
Statistical Study ◽  
Molar Absorptivity ◽  
Confidence Limits ◽  
Components Of Variance ◽  
Significant Difference ◽  
Single Determination ◽  
Comparison Measurements ◽  
Analytical Standards

Abstract Measurements of molar absorptivities in methanol were carried out by two laboratories on samples of anatoxins Bi and Gi prepared and purified independently in four laboratories and on samples of aflatoxins B2 and G2 prepared and purified independently in three laboratories. Molar absorptivities of pure aflatoxins Bi, B2, G1, and G2 in benzene-acetonitrile (98 + 2) were determined at two laboratories. With the exception of aflatoxin G2, no significant difference between aflatoxin samples could be demonstrated. Molar absorptivity values and absorbance ratios for each aflatoxin, based on these data, are given. Statistical 95% confidence limits were established for a single determination of molar absorptivity. A statistical study was made of the components of variance which contribute to the accuracy of the determination of molar absorptivity. A comparison of the fluorescence intensities of spots of various aflatoxin preparations, developed on silica gel-coated thin layer plates, with the amount of aflatoxin in each spotting solution as determined by absorbance measurements, demonstrated the validity of using absorbance and fluorescence comparison measurements for aflatoxin quantitation.

Mechanism of interference with the Jaffé reaction for creatinine.

1987 ◽  
Vol 33 (7) ◽  
pp. 1129-1132 ◽  
Author(s):  
M H Kroll ◽  
N A Roach ◽  
B Poe ◽  
R J Elin
Keyword(s):  
Carbonyl Group ◽  
Equilibrium Constants ◽  
Molar Absorptivity ◽  
Reaction Products ◽  
Cyclic Ketones ◽  
Common Structure ◽  
Aliphatic Ketones ◽  
Rate Of Reaction ◽  
The Common

Abstract We investigated the mechanism of the Jaffé reaction for determination of creatinine by studying the spectrophotometric, kinetic, and equilibrium properties of the reaction of picrate with creatinine and with cyclic and aliphatic ketones. Absorbance spectra for the reaction products of picrate with all the ketones were superimposable with that of creatinine (Amax, 490 nm). Cyclic ketones not containing nitrogen had a molar absorptivity less than half that of creatinine and equilibrium constants approximately 0.01 that of creatinine. Aliphatic ketones, except for benzylacetone, had molar absorptivities similar to that of creatinine, but all of these compounds had equilibrium constants approximately a tenth or less that of creatinine. The common structure for all of the compounds reacting with picrate is the carbonyl group. The variable magnitude of interference for aliphatic and cyclic ketones is ascribable to the different rate constants, molar absorptivities, and equilibrium constants as compared with creatinine. Structures adjacent to the carbonyl group significantly affect the absorptivity and equilibrium constant, but steric hindrance is the major factor affecting the rate of reaction. We postulate that the carbonyl group is required for the Jaffé reaction, and we suggest a mechanism for the reaction.

Determination of Sorbitol in Bakery Products

1966 ◽  
Vol 49 (6) ◽  
pp. 1180-1183
Author(s):  
Harvey K Hundley ◽  
Duane D Hughes
Keyword(s):  
Ion Exchange ◽  
Thin Layer ◽  
Alkaline Solution ◽  
Ion Exchange Resins ◽  
Bakery Products ◽  
Reaction Products ◽  
Sugar Alcohols ◽  
Exchange Resins ◽  
Layer Chromatography

Abstract Sorbitol is extracted from bakery products with water, and nonreducing sugars are inverted by acid hydrolysis. Carbohydrates other than the sugar alcohols are degraded in alkaline solution and reaction products are removed by ion exchange resins. Sorbitol is determined by the amount of periodate consumed in oxidation and identified by thin layer chromatography.

Colorimetric Determination of Certain Phenothiazine Drugs by Using Morpholine and Iodine-Potassium Iodide Reagents

1986 ◽  
Vol 69 (3) ◽  
pp. 513-518 ◽  
Author(s):  
Adel F Youssef ◽  
Salwa R El-Shabouri ◽  
Fardous A Mohamed ◽  
Abdel Maboud I Rageh
Keyword(s):  
Potassium Iodide ◽  
Quantitative Estimation ◽  
Colorimetric Method ◽  
Molar Absorptivity ◽  
Dosage Forms ◽  
Colorimetric Determination ◽  
Reaction Products ◽  
Phenothiazine Drugs ◽  
Lower Molar

Abstract A colorimetric method was developed for the quantitative estimation of 11 phenothiazine drugs. The method is based on the interaction of unsulfoxidized drug with morpholine and iodine-potassium iodide reagents. The interaction for all studied phenothiazine drugs yields a blue product with 2 absorption maxima: one in the range of 620-640 nm with lower molar absorptivity and the other in the range of 662-690 nm with higher molar absorptivity. The color was stable for at least 10 h. The reproducibility and recovery of the method were excellent. The method was applied successfully to the analysis of various commercially available phenothiazines in different dosage forms. The results were comparable to those obtained by official procedures. The suitability of the method for detection and estimation of promethazine excreted in urine has been suggested by preliminary experiments. Reaction products have been isolated and identified.

scholarly journals Rat Serum Carboxylesterase Partly Hydrolyses Gamma-Butyrobetaine Esters

2009 ◽  
Vol 60 (2) ◽  
pp. 147-156 ◽  
Author(s):  
Lida Bagdonienė ◽  
Danutė Labeikytė ◽  
Ivars Kalviņš ◽  
Veronika Borutinskaitė ◽  
Aleksandrs Prokofjevs ◽  
...  
Keyword(s):  
Blood Serum ◽  
Esterase Activity ◽  
Colorimetric Determination ◽  
Reaction Products ◽  
Rat Serum ◽  
Rat Blood ◽  
Optical Absorbance ◽  
Hydrolysis Of ◽  
Related Compounds

Rat Serum Carboxylesterase Partly Hydrolyses Gamma-Butyrobetaine EstersAlthough described some time ago, gamma-butyrobetaine esters and related compounds have not gained much attention from researchers, and their physiological function remains obscure. Formerly we detected GBB-esterase enzymatic activity in rat blood serum using phenylated gamma-butyrobetaine as an artificial substrate of the enzyme and HPLC. The aim of the present work was to develop an assay that would enable spectrophotometric or colorimetric determination of the reaction products of GBB-esterase activity and to reveal individual proteins performing GBB-esterase activity in rat blood serum. For this purpose gamma-butyrobetaine 1-naphthyl ester was synthesised. Hydrolysis of this ester releases 1-naphthol, which increases the optical absorbance at 322 nm. We have shown that the enzymatic hydrolysis of GBB 1-naphthyl ester to 1-naphthol in rat blood serum is due to GBB-esterase activity. An attempt was done to purify the enzyme from rat blood serum. By combining DEAE Sepharose at pH 4.2 and affinity chromatography with procainamide we achieved a 68-fold enrichment of GBB-esterase activity in our preparations. Separation of fraction proteins in 2D protein electrophoresis with following mass-spectrometry indicated that GBB esterase activity in rat blood serum is performed in part by carboxylesterase.

scholarly journals Synthesis of a new organic probe 4-(4 acetamidophenylazo) pyrogallol for spectrophotometric determination of Bi(III) and Al(III) in pharmaceutical samples

2021 ◽  
Vol 40 (1) ◽  
pp. 108-126
Author(s):  
Jumana W. Ammar ◽  
Zainab A. Khan ◽  
Marwa N. Ghazi ◽  
Naser A. Naser
Keyword(s):  
Pharmaceutical Formulations ◽  
Molar Absorptivity ◽  
Scanning Calorimetry ◽  
Spectrophotometric Methods ◽  
Modern Development ◽  
Relative Standard ◽  
Visible Spectra ◽  
Ft Ir ◽  
Linear Solvation Energy

Abstract A modern development discusses the synthesis and validity of simple, sensitive, and versatile spectrophotometric methods for Bi(III) and Al(III) determination in pharmaceutical formulations have been conducted. In the present paper, 4-(4 acetamidophenylazo) pyrogallol has been synthesized as a new organic compound, 4-APAP, by coupling pyrogallol in a regulated pH medium with diazotized p-aminoacetanilide. 4-APAP was identified by methods of FT-IR, 1H-NMR, 13C-NMR, and thermal analysis (thermogravimetry and differential scanning calorimetry). Solvatochromic activity was also studied in solvents with different polarities. The Kamlet and Taft linear solvation energy relationship was used to correlate shifts in UV-Visible spectra of 4-APAP with Kamlet-Taft parameters (α, β, and π*). The optimum assay conditions showed linearity from 0.3–13 to 0.5–11 μg·mL−1 for Bi(III) and Al(III), respectively. Molar absorptivity values were 3.365 × 104 and 0.356 × 104 L·mol−1·cm−1 for Bi(III) and Al(III), with similar Sandell's sensitivity measures of 0.006 and 0.008 μg·cm−2. Detection limits and quantification limits were 0.013 and 0.043 μg·mL−1 for Bi(III), respectively, and 0.018 and 0.059 μg·mL−1 for Al(III) with the relative standard deviation for determination of both metal ions using 4-APAP probe being <2.0%. The validity, accuracy, and efficiency of the approaches were demonstrated by the determination of Bi(III) and Al(III) in different formulations.

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