Presence Of Potassium Dichromate Research Articles

Kinetics, thermodynamics, and DFT studies of phenols oxidative coupling reactions with 4-amino-N, N-dimethylaniline

A spectrophotometric method has been established for the reaction kinetics of phenol oxidative coupling with 4-amino-N, N-dimethylaniline in the presence of potassium dichromate as an oxidant to form C14H14N2O, known as phenol blue. Optimum conditions for the reaction were investigated: maximum wavelength (λ max), linear range, molar absorptivity, and stability constant. The kinetic models were applied to the reaction, indicating that it is a first-order reaction. The activation energy (Ea) and Arrhenius constant (A) were calculated from the Arrhenius equation as 14.89 kJ·mol−1 and 3.75 × 105 s-1 respectively. Thermodynamic parameters were ΔH* 12.37 Kj·mol−1, ΔG* 5.47 kJ·mol−1 and ΔS* 22.77 J·mol−1·K−1 at 30oC.. Results indicate that the formation of the product phenol blue is non-spontaneous and endothermic in nature. Density function theory (DFT) has been done for the comparison between experimental and theoretical results using the common 6-311G(d,p) basis set. The results are in good agreement with each other, proving the reliability of the method. Finally, some preliminary test has been performed to check possibility of the product as dye.

Spectrophotometric Determination of Loperamide Hydrochloride in Pure and Pharmaceutical Dosage Forms Using Oxidative Coupling Reaction

Abstract Phenothiazine reagent in the presence of potassium dichromate was used for determination of loperamide (LPM) depending on oxidative - coupling reaction to create a blue soluble measured at 625 nm against blank solution, the absorbances values exhibit clear and close relation with the real amount of LPM. Linearity was from 0.8 to 40 μg.ml-1 of LPM. Molar absorptivity was 0.3799×104 l.mol-1.cm-1, Sandell's sensitivity was 0.1351μg ∕cm 2, limit of detection and limit of quantitation were 0.33918, and 1.1306 μg /ml respectively. The method was used for determination of three dosage forms of LPM; Loperamide 2 mg/tablets Medochemie Ltd, Limassol-Cyprus (Europe), Loperamide 2 mg/tablets Safa Co. - Diala (Iraq) and Loperamide 2 mg/capsules Janssen pharmaceuticals (Belgium).

Spectrophotometric Determination of carvedilol Via Oxidative Coupling Reaction

A simple, fast and sensible spectrophotometric method was developed for the determination of carvedilol. The method is based on the oxidative coupling reaction of the compound with phenothiazine in the presence of potassium dichromate as oxidant to form a stable pink-red color product showing maximum absorption at 551nm. Molar absorptivities are 1.625 ×104 l. Mol-1, cm-1. The Beer law has been complied with in a range from (1 to 12) ppm. This method has been successfully applied to carvedilol analysis in various pharmaceutical formulations.

Selective room-temperature leaching of copper from mechanically activated copper smelter slag

Herein, the room-temperature sulfuric acid leaching of copper smelter slag powder in the presence of potassium dichromate was investigated, resulting in the selective extraction of copper with its separation from zinc and iron. To enhance the extraction of copper, mechanical activation in the planetary ball mill and attritor was used. The Taguchi method was applied to determine the optimal conditions for both mechanical activation and leaching. For mechanical activation in the attritor, a rotation speed of 1200 rpm, ball-to-powder ratio of 40 and milling time of 75 min were ideal. Under these conditions, the specific surface area (SBET) could be increased from 1.7 m2/g, for the starting slag, to 59.4 m2/g. According to ANOVA, the most important factor is the rotation speed. For comparison, the slag was subjected also to planetary ball milling using the same conditions and a specific surface area of 116 m2/g was obtained. Leaching conditions that maximize copper recovery and, independently, copper selectivity, were also found. The maximum copper recovery was 87.3%, while the maximum copper selectivity was 97.9%. The most influential parameters in leaching were the concentration of K2Cr2O7 and the liquid-to-solid ratio. The copper selectivity is attributed to better solubility of chalcopyrite (CuFeS2) in comparison with zinc ferrite (ZnFe2O4) and fayalite (FeSiO4) containing the other metals. This study provides a statistical approach for planning the experiments of pretreatment and leaching to efficiently recover valuable metals from secondary raw resources in an environmentally interesting fashion by using low concentrations of leaching agents and mechanical pretreatment.

Oxidative stress responses of juvenile catfish, Clarias gariepinus exposed to potassium dichromate at sublethal concentrations in south-eastern Nigeria

The oxidative stress responses of Clarias gariepinus exposed to potassium dichromate at sublethal concentrations for 28 days were studied in 2017. Fish were exposed to 0.165, 0.0825 and 0.033 mg l−1 corresponding to 1/10, 1/20 and 1/50 of the 96 h LC50 of 1.65 mg l−1. Haematological parameters of fish decreased in haemoglobin when compared with the control and there was reduction of mean corpuscular haemoglobin concentration, mean corpuscular haemoglobin and mean corpuscular volume in presence of potassium dichromate. Significant increase in white blood cells throughout the duration of exposure and decrease in lymphocytes were observed. The lipid peroxide levels were increased in test concentrations when compared with controls of liver and gill. The fish group was subjected to oxidative stress, because of lipid peroxidation in response to reactive oxygen species generation. Gill and liver tissues showed concentration and time dependent significant increase (p < 0.05) in values of malondialdehyde, catalase and superoxide dismutase, whereas there was reduced glutathione. Similarly, potassium dichromate enhanced levels of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase as both concentration and time dependent when compared with control. Micronuclei induction was highest (7.55) on day 14 in all concentrations in the peripheral blood cells. There were alterations in values of glutathione peroxidase, superoxide dismutase, and catalase during exposure and recovery periods.

Espectroscopia no Infravermelho Próximo para a Quantificação de Carbono em Solos da Bacia do Acre

In soil carbon determination various techniques are used, predominating in Brazil methods based on oxidation of organic matter in the presence of potassium dichromate in an acidic medium and the elemental analysis. The objective of this study was to evaluate the technical viability of NIR spectroscopy combined with multivariate calibration analysis to quantify the carbon content of the soil Acre basin. We use 190 soil samples, collected in various locations of Acre basin, in order to test the NIR technique for determining the soil carbon content. We compared the NIR technique, dichromate oxidation in acidic media and elemental analysis methods. The amounts of carbon was obtained by oxidation and elemental analysis methods using the method of elemental analysis as a reference, it is found that the oxidation method recovered an average of 63.8% of carbon determined by the reference method. We suggest to adjust the amount of carbon obtained by the oxidation method should be adopted the coefficient 1.55. Regarding the use of NIR spectroscopy, the model developed for soil carbon analysis Acre basin by NIR spectroscopy showed good classification according to R 2 values and excellent rating under the RMSEC < RMSEP and RPD values, with reference to carbon determined by the elemental analysis method. Keywords : organic matter; Amazon; tropical soils; analytical methods.

Combined effect of salinity and pollution with potassium dichromate on adaptive capacity of diatom benthic microalga &lt;i&gt;Attheya ussurensis&lt;/i&gt; in laboratory environment

Combined effect of two stress factors (decreasing of salinity and presence of potassium dichromate in the medium) on adaptive capacity of benthic alga Attheya ussurensis is investigated. The salinity decreasing to 20 ‰ combined with 0.01 mg/L of K 2 Cr 2 O 7 in the medium didn’t cause any change of the cells growth in number, as compared with uncontaminated environment (32 ‰, control), or changes in their morphology. The same salinity decreasing with K 2 Cr 2 O 7 concentration 0.10 mg/L caused a lowering of the cells growth to 86 % of the control value by the end of experiment that was accompanied by minor morphological abnormalities, as cells elongation in pervalvar axis direction and granulation of chloroplasts. In the second seeding, there was no change of the cells growth again under the low concentration of K 2 Cr 2 O 7 and their adaptation to the concentration 0.10 mg/L was observed: in the end of experiment the cells number had no significant difference from the control one. The salinity decreasing to 16 ‰ with the toxicant concentration 0.01 mg/L caused a lowering of the cells growth in the 4 th day that persisted until the end of experiment and some insignificant changes of their morphology. The same salinity decreasing with the toxicant concentration 0.10 mg/L caused a significant drop of the cells number with strong negative morphological changes; moreover, the alga wasn’t able to adapt to this combined stress after re-seeding.

Micro Determination Study and Organo physical properties Of Resorcinol with Thiamine in the Presence of Potassium Dichromate

Objective: This study aims to estimate Resorcinol (3- hydroxy phenol). Methodology: The study was through the development of a simple and high sensitivity and selectivity to estimate Resorcinol (3- hydroxy phenol) and The method is based on the reaction of Resorcinol (3-hydroxyphenol) with Thiamine (Vitamin B1) and potassium Dichromate at pH 3.5. So The reactions gave an intense water soluble color products that have maximum absorption at 510 nm. Results: This study showed that the ε max for 3- hydroxy phenol is (0.145 Χ 104 liter. Mol-1 .cm-1), A linear correlations (1-9 μg ml-1) for 3-hydroxyphenol compound was found between absorbance at λmax and concentration. The accurate (relative error was better than -0.2 %) and precise ( RSD was better than 1.2%). The colored product was found to be 1:1 (3-hydroxyphenol : Thiamine). The stability constant of the reaction under optimized conditions at room temperature was 3.25 Χ 105 L. mole-1 . Recommendations: The study recommends the appointment of phenolic compounds or other phenolic derivatives are relying on this method any use of thiamine and oxidized worker himself (potassium dichromate).

Research on the Role of Pre-Oxidation in the Separation of Cu-Pb in the Presence of Potassium Dichromate

It is the most effective method to use potassium dichromate to separate copper from lead when galena is oxidized. However, it needs long time to oxidize galena by potassium dichromate. The efficiency of five oxidants on potassium dichromate depressing ability to galena have been studied completely in this paper, and results suggest that separation of Cu-Pb can be carried out effectively in short time in the presence of potassium dichromate when galena is pre-oxidized by oxidants. Sodium hypochlorite is the best oxidant, and after the interaction of 15 min., the grade and the recovery of copper concentrate are 24.02% and 81.93% respectively, and the grade and the recovery of lead concentrate are 17.88% and 84.98% respectively.

Reversible immobilization of uricase on conductive polyaniline brushes grafted on polyacrylonitrile film

Polyacrylonitrile film (PAN) surfaces were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The conductive films were used for immobilization of uricase. The surface resistance of the conductive film in this work was found to be 0.97 kΩ/cm. The maximum amount of immobilized enzyme on conductive film containing 2.4% PANI was about 216 μg/cm(2). The optimum pH for free and immobilized enzymes was observed at 7.0 and 7.5, respectively. The K (m) values for free and immobilized uricase were found to be 94 and 138 μM, respectively. V (max) values were calculated as 1.87 and 1.63 U/mg protein for the free and immobilized enzymes, respectively. Immobilized uricase exhibited ~68% of its original activity even after 2 months of storage at 4 °C while the free enzyme lost its initial activity within 4 weeks.

Surface modification of polyacrylonitrile film by anchoring conductive polyaniline and determination of uricase adsorption capacity and activity

Polyacrylonitrile (PAN) films were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The effect of aniline concentration on the grafting efficiency and on the electrical surface resistance of PAN and (PAN/PANI)-1–3 composite film was investigated. The surface resistances of the conductive composite films were found to be between 6.32 and 0.97 kΩ/cm. As the amount of grafted PANI increased on the PAN films, the electrical resistance of composite film decreased. The PAN/PANI composite films were also characterized using SEM and FTIR. The changes in the surface properties of the films were characterized by contact angle measurements. As expected, the PAN, PAN/PANI and PAN/PANI-uricase immobilized films, exhibited different contact angle values and surface free energy due to different interactive functional groups of the films. The conductive films were well characterized and used for immobilization of uricase. The amount of adsorbed enzyme increases with the increase of surface concentration of grafted fibrous polyaniline polymer. The maximum amount of immobilized enzyme onto composite film containing 2.4% PANI was about 216 μg/cm 2 (i.e., PAN/PANI-3). The immobilized uricase was reused 24 times in batch wise assay in a day. Finally, the immobilized uricase enzyme system was successfully fabricated and applied to determine the uric acid level in human serum samples.

Polyaniline grafted polyacylonitrile conductive composite fibers for reversible immobilization of enzymes: Stability and catalytic properties of invertase

Polyacylonitrile fibers (PAN) surfaces were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The effect of aniline concentration on the grafting efficiency and on the electrical surface resistance of PAN/PANI composite fibers was investigated. The surface resistance of the conductive composite fibers in this work was found to be between 8.0 and 0.5 kΩ/cm. As the amount of grafted PANI increased on the PAN fibers the electrical resistance of composite fibers decreased. The PAN/PANI composite fibers were characterized by SEM and FTIR studies. Composite PAN/PANI fibers were used for reversible immobilization of invertase. The immobilization efficiency and the activity of the immobilized invertase (from 1.0 mg/mL invertase solution at pH 5.5) were increased with increasing PANI contents of the composite fibers. The maximum amount of immobilized enzyme onto composite fibers containing 2.0% PANI was about 76.6 mg/g. The optimum pH for the free enzyme was observed at 5.0. On the other hand, immobilized invertase yielded a broad optimum pH profile between pH 5.0 and 7.0. Immobilized invertase exhibited 83% of its original activity even after two months storage at 4 °C while the free enzyme showed only 7% of its initial activity.

Flow- Injection Spectrophotometric Determination of some Sulpha Drugs via Oxidative Coupling with 4-Amino-N, N-diethylaniline. Application to Various Samples

A flow injection spectrophotometric method is described for the determinaiton of sulphonamides&#x0D; in aqueous and biological samples. The method is based on the oxidative coupling reaction of 4-amino-N,&#x0D; N-diethylaniline with sulphonamide drugs in the presence of potassium dichromate as oxidizing agent.&#x0D; Intense violet, water soluble dye was obtained which has a maximum absorption at 550nm,. Linear&#x0D; calibration graphs were obtained for different sulphonamides with a molar absorpitivity of 4200-5270 l mol-1 cm-1&#x0D; and a relative standard deviation less than 0.56%. The proposed method has proved to be highly sensitive (detection limit range 0.30-0.63 μg ml-1 sulphonamide) and accurate (recovery % was 98.2-101.2%). The nature of the coloured dye and its stability constant were determined. The method was applied successfully to the determination of sulphonamide drugs in pharmaceutical preparations, blood and urine samples.Keywords: FIA, Spectrophotometer 4-amino-N, N-diethylaniline

Spectrophotometric Determination of Phenols in Aqueous Solution via Oxidative-Coupling Reaction with 4-Amino-N,N-Diethylaniline and Potassium Dichromate

A simple and sensitive spectrophotornetric method for the determination ofphenol has been developed. The method is based on the oxidative-coupling reaction ofphenol with 4-amino-N,N-diethylaniline in the presence of potassium dichromate at pH 6 solution to form an intense bluish-green water-soluble dye that is stable and has a maximum absorption at 670nm. A plot of absorbance versus concentration shows that Beer's law is obeyed over the concentration range of 2.5-250 jag of phenol in a final volume of 25ml,(i-e 0.1-lOppm) with a molar absorptivity of 3.95 x 104 l.mor'cm"', a percentage recoveries of 98.10-100.75% and a relative standard deviation of better than ±0.4%, depending on the concentration level. The optimum conditions for full colour development are described and the proposed method is extended to some other phenolic compounds.

Spectrophotometric Estimation of Nimesulide and its Formulations

Four simple and sensitive visible spectrophotometric methods (A–D) have been described for the assay of nimesulide (NMD) either in pure form or in pharmaceutical formulations. Methods A and B are based on the oxidative coupling between the reduced product of NMD (RNMD) and p-N,N-dimethyl phenylenediamine dihydrochloride (DMPD) in presence of chloramine – T (CAT) or 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in presence of ferric chloride (Fe III) to form coloured products with λmax at 540 nm and 600 nm respectively. Method C is based on the diazotization of RNMD with excess nitrous acid (HNO2) and estimating the consumed HNO2 with cresyl fast violet acetate (CFVA). Method D is based on the formation of the coloured charge-transfer complex, when RNMD is treated with metol (p-methyl aminophenol sulphate, PMAP) in presence of potassium dichromate. All variables have been optimized and the reaction sequence is presented. The concentration measurements are reproducible within a relative standard deviation of 1.0%. Recoveries are 98.6–100.2%.

Determination of aluminium in human blood and serum by graphite furnace atomic absorption spectrometry using potassium dichromate matrix modification

A method for the direct determination of aluminium in human blood and serum by graphite furnace atomic absorption spectrometry using potassium dichromate as a matrix modifier has been developed, which eliminates the need to prepare matrix-matched standards or the use of a standard additions method, techniques which are frequently quoted in the literature. The sensitivity for the determination of aluminium was increased by a factor of two in the presence of potassium dichromate over that in the absence of a matrix modifier. The mechanism of this enhancement effect of matrix modification was studied by measuring the molecular absorption of AlO and Al2C2 which are observed in the initial stage of the atomisation process. The recommended method has been applied to the determination of aluminium in human blood and serum.

Lysozyme Activity of High-Leucocyte-Count Milk and the Effect of Heat and Potassium Dichromate on Lysozyme Activity

No support could be found for the hypothesis that mastitis, as evidenced by increased leucocyte counts in milk, is accompanied by an increase in lysozyme activity. The presence of potassium dichromate in the preserved milk samples did not seem to affect lysozyme activity. The sensitivity of lysozyme to heat was demonstrated. All lysozyme isolates and purifications were made with deaminated chitin affinity chromatography.

A wet-combustion method for the determination of chlorine in coals

Chlorine in coals can be determined by wet-combustion with sulphuric acid in the presence of potassium dichromate and silver sulphate. The liberated chlorine is absorbed in hydrogen peroxide and after treatment with mercuric oxycyanide is determined acidimetrically. The method is simple, fairly rapid and should be suitable for multiplicate analysis. The results agree well with those given by two independent methods of analysis, i.e. incineration with Eschka mixture followed by the Volhard titration, and the high temperature combustion method.