Electrochemical study of iodide in the presence of barbituric acid. Application to coulometric titration of barbituric acid

Spectrophotometric reaction rate method for determination of barbituric acid by inhibition of the hydrochloric acid-bromate reaction

A new kinetic-spectrophotometric method was developed for the determination of barbituric acid. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolorization of methyl orange by the reaction products was used to monitor the reaction spectrophotometrically at 510 nm. The variable affecting the rate of the reaction was investigated. The method is simple, rapid, relatively sensitive and precise. The limit of detection is 7.9x10(-7) M and calibration rang is 1x10(-6)-6.0x10(-4) M barbituric acid. The linearity range of the calibration graph is depends on bromate concentration. The relative standard deviation of seven replication determination of 5.6x10(-6) M barbituric acid was 1.8%. The influence of potential interfering substance was studied.

Electrooxidation of iodide in the presence of 4-hydroxycoumarin: application to a simple coulometric titration of 4-hydroxycoumarin

The electrochemical oxidation of iodide ion in the presence of 4-hydroxycoumarin (1) was studied using cyclic voltammetry and controlled-potential coulometry. The result indicates that the resulting iodine takes part in a halogenation reaction and reacts with 4-hydroxycoumarin (1). According to the obtained results, a new and simple coulometric titration method with potentiometric end-point detection for the determination of 4-hydroxycoumarin (1) is presented. In the presented method, 2-200 micromol of 4-hydroxycoumarin (1) was successfully determined.

Determination of barbituric acid, utilizing a rapid and simple colorimetric assay

Barbituric acid is widely used in the manufacturing of plastics, textiles, polymers, and pharmaceuticals. Three assay methods are presented, which can utilize either aqueous or solid samples. The detection of as little as 10 microg of barbituric acid can be accomplished, either as an aqueous or solid sample, when using micro reaction tubes. The red-violet endpoint is easily discerned and results upon the formation of a violuric acid derivative. A Spot Test protocol is described which allows for a positive/negative indication of barbituric acid presence. The Spot Test is sensitive to as little as 18.75 microg/ml of barbituric acid. The construction of a Standard Curve for assaying multiple samples and over longer time periods is demonstrated, and is shown to be linear from 18.75 microg/ml to 2.25 mg/ml of barbituric acid. Spectrophotometer readings are made from an absorption peak appearing at 530 nm. The molar absorptivity of the violuric acid derivative is calculated to be 31.4 per mol/l per cm. The micro reaction tube assay will quantitate as little as 10 microg of barbituric acid through interpolation with controls containing a known amount of analyte. Inorganic salts such as NaCl, NaN(3), LiBr, and CaCO(3) do not interfere with endpoint determination. Many organic compounds (also pharmaceuticals) do not inhibit the reaction.