Potassium Dichromate In Acid Medium Research Articles

The effect of transition metal ions (M2 + = Mn2 +, Ni2 +, Co2 +, Cu2 +) on the chemical synthesis polyaniline as counter electrodes in dye-sensitized solar cells

The effect of transition metal ions (M2+=Mn2+, Ni2+, Co2+, Cu2+) on the chemical synthesis of polyaniline (PANI) used as a platinum-free counter electrode (CE) in dye-sensitized solar cells (DSSCs) was investigated. PANI was synthesized by co-polymerization of aniline in the presence of different transition metal ions by using potassium dichromate in acidic medium. It was found that the ion doping of PANI showed a certain catalytic activity for the regeneration of traditional iodide/triiodide (I−/I3−) redox couples. The power conversion efficiency (η) of PANI CEs doped with Mn2+, Ni2+, Co2+ (4.41%, 2.36% and 2.10%, respectively) were higher than 1.94%, the value measured for PANI CE without doping. Doping with Cu2+ decreased the power conversion efficiency of PANI CE (PANI-Cu2+η=1.41%). The electrical properties of the PANI, PANI-Ni2+, PANI-Co2+, PANI-Mn2+ and PANI-Cu2+ were studied by cyclic voltammetry (CV), impedance (EIS), and Tafel polarization curve. The experimental results confirmed that PANI was affected by the doping of different transition metal ions (M2+=Mn2+, Ni2+, Co2+, Cu2+). These results indicate a potential application of ion doped PANI as counter electrode in cost-effective DSSCs.

Alternative non-chromatographic method for alcohols determination in Clostridium acetobutylicum fermentations

An economic, simple, quantitative, and non-chromatographic method for the determination of alcohols using microdiffusion principle has been adapted and validated for acetone-butanol-ethanol (ABE) fermentation samples. This method, based on alcohols oxidation using potassium dichromate in acid medium, and detection by spectrophotometry, was evaluated varying, both, temperature (35°C, 45°C, and 55°C) and reaction time (0 to 125min). With a sample analysis time of 90min at 45°C, a limit of detection (LOD), and a limit of quantification (LOQ) of 0.10, and 0.40g/L, respectively. The proposed method has been successfully applied to determine butanol and ethanol concentrations in ABE fermentation samples with the advantage that multiple samples can be analyzed simultaneously. The measurements obtained with the proposed method were in good agreement with those obtained with the Gas Chromatography Method (GCM). This proposed method is useful for routine analysis of alcohols and screening samples in laboratories and industries.

Application of brominating agents and potassium dichromate for the spectrophotometric determination of captopril in pharmaceutical formulations

Three simple and sensitive spectrophotometric methods were developed for the estimation of captopril (CAPT) in pure form or in tablet formulations. The three methods are based on the reactivity of the thiol group. The first two methods (A and B) are based on the oxidation of CAPT by bromate/bromide mixture of known concentration in acid medium. In method A, the determination of the residual bromine is based on its ability to bleach the methylene blue dye and measuring the absorbance at 664 nm. Method B involves treating the unreacted bromine with a measured excess of iron(II) and the remaining iron(II) is complexed with 2,2 � -dipyridyl and the increase in absorbance is measured at 523 nm. Method C involves the addition of a known excess amount of potassium dichromate in acidic medium, followed by the estimation of unreacted amount of dichromate by reacting with excess of iron(II). The resulting iron(III) is complexed with thiocyanate and the absorbance is measured at 478 nm. In all the methods, the amount of oxidant reacted corresponds to the drug content. The different experimental parameters affecting the development and stability of the color product are carefully studied and optimized. After validation, the proposed methods were successfully applied to assay of CAPT in its commercial tablets. No interference was observed from common additives found in pharmaceutical preparations. The results were statistically compared with those of a reference method by applying Student's t- and F-test.

Spectrophotometric Determination of Chromium in Water, and Pharmaceutical Samples Using 1-Naphthol

Facile and sensitive spectrophotometric methods for the determination of trace and ultra trace amounts of chromium (VI) are described. 4-aminoantipyrine (APP) reacts with 1-naphthol (NPL) in presence of oxidising agent potassium dichromate in acidic medium to produce red coloured product having λmaxof 485 nm. The molar absorptivity and Sandell's sensitivity were 2.07x104l mol-1cm-1and 0.00240 μg/cm2respectively. The colour is stable for more than 6 h. The system obeys Beer's law in the range, 2-18 μg for determination of chromium (VI). The detection limits of chromium (VI) is 0.048 μg mL-1. The method is highly reproducible and has been applied to the analysis of chromium in synthetic, natural water samples and pharmaceutical preparations and the results compared favourably with the reported method.

Spectrofluorimetric determination of some dibenzazepine drugs

A convenient and sensitive spectrofluorimetric method for the detn. of 6 dibenzazepine drugs: imipramine-​HCl, desipramine-​HCl, clomipramine-​HCl, trimipramine maleate, opipramol-​2HCl and carbamazepine was developed. The method depends on the oxidn. of the compds. with potassium dichromate in acid medium. The relative fluorescence intensities for all 6 drugs were measured at an excitation wavelength range of 350-​360 nm and an emission wavelength range of 460-​485 nm against a reagent blank prepd. similarly. The drugs could be detd. successfully in the concn. range of 0.1-​3.0 μg​/mL. The method was satisfactorily applied to their detn. in pharmaceutical prepns. and in spiked plasma samples. The results were in good agreement with those from official methods.

Spectrophotometric determination of organic carbon in soil

Abstract A detailed study was made of the well‐known organic carbon determination that is based on measuring the absorbance of the green chromium(III) complex generated when organic matter is oxidized by potassium dichromate in acidic medium. The green chromic colour proved to be unstable, turning slowly to a violet colour. It was also found that chromic sulphate exerts a catalytic influence on the decomposition of excess dichromate. Based on this work, a modified method was developed which is simple, rapid, and very accurate when working under carefully controlled conditions.

Spectrophotometric Determination of Some Dibenzazepines

Abstract Simple and sensitive method is proposed for determination of four di-benzazepine derivatives. The method is based on the oxidation of dibenzazepines by potassium dichromate in acid medium. The reaction was followed spectrophoto-metrically by measuring the rate of change in absorbance of the coloured products at 670 nm. Linear calibration graphs from 5-50 μg/ml of the final solutions are obtained for all the studied drugs. The method has been successfully applied to the determination of dibenzazepines in some commercial and laboratory prepared tablets. The results were compared statistically with those obtained by official procedures.

AUTOMATED ANALYSIS OF SORBIC ACID IN FOOD PRODUCTS

ABSTRACTThe increasing use of sorbic acid and sorbates has created a need for a rapid, reliable and accurate analytical procedure for the routine analysis of these materials in food products. In this paper is described an automated version of the most popular calorimetric (thiobarbituric acid) method, originally proposed by Schmidt. The procedure uses a gas diffusion membrane in lieu of steam distillation for the separation of sorbic acid from the food samples. The separated acid is cleaved with potassium dichromate in acidic medium to yield an intermediate malon‐aldehyde, which in turn, when reacted with thiobarbituric acid, produces a red dye. The absorbance of the red color, measured at 530 nm was proportional to the concentration of the sorbic acid in the sample. This automated procedure is capable of analyzing 30 samples per hour.

Collaborative Study of the Colorimetric Determination of Sorbic Acid in Cheese

Abstract After isolation of sorbic acid from cheese by steam distillation, the acid recovered is cleaved with potassium dichromate in acidic medium to form an intermediate malonaldehyde, which, in turn, reacts with 2-thiobarbituric acid to produce a red dye. The absorbance of the red color, measured at 532 nm, is proportional to the concentration of sorbic acid in the sample. Seven collaborators reported recoveries of 96.7–102.4% from cheese samples spiked with 0.05% sorbic acid. This method has been adopted as official first action.