Spectrophotometric Determination Of Selenium Research Articles

Spectrophotometric Determination of Selenium in Food Items

Selenium (Se) is an essential element that is obtained from food. To increase the level of selenium in the body, we should consume selenium-rich foods in our diet. The objective of this study was to develop a simple spectrophotometric method for the quantitative analysis of selenium present in food. This study included six food items such as broccoli, cabbage, red cabbage, fenugreek, garlic, and ginger. The new method is based on the yellow colour complex formed by the reaction between 2% potassium iodide and 0.2% pyridine in acidic medium with the selenium. Absorbance was measured at 400 nm against the reagent blank. The results of the above proposed method were compared with the reference method of using potassium iodide and starch as reagents. The selenium content in the examined food samples was determined from the regression equation of the calibration curve y= 0.0799x+0.3477 respectively. All the analyses were performed in triplicate, and the results are expressed as mean ± standard deviation. The highest mean selenium value was obtained in ginger and garlic 18.70 & 18.32 µg/g, respectively among all the studied samples, while the lowest value was in fenugreek seeds 7.38 µg/g. The proposed method is simple, rapid, sensitive, and obeys Beer–Lambert’s law. The proposed method was successfully applied to determine food items. Selenium has been quantitatively analysed for its potential to protect the body from many degenerative diseases. Selenium-rich food, as studied here, should be used as a supplement in the human diet.

Spectrophotometric Determination of Selenium (IV) Using 4,5-diamino-o-xylene as a New Chromogenic Reagent

A simple, rapid, and sensitive spectrophotometric method for the determination of selenium (IV) based on the formation of a 1:2 complex with 4,5-diamino-o-xylene (DAX) as a new sensitive and selective chromogenic reagent is developed. The DAX reacts with selenium (IV) in the presence of citric acid to form a complex in the pH range of 1.0 2.2. The experimental conditions for determining selenium including the influences of pH, reagent concentration and time were evaluated and optimized. Under the optimum experimental conditions, the molar absorptivity of the complex was 1.27×104 L/mol–1 cm–1 at 340 nm. Beer's law is obeyed in the range of 1≃12 µg/mL–1. The limits of detection and quantization were 0.948 µg mL-1 and 3.16 µg/mL-1 respectively. The interfering effect of some cations and anions was also studied. This method can be applied to the direct and easy determination of selenium species as organic, inorganic, Se(VI) and Se(IV) in a variety of real samples.

A simple and sensitive vortex-assisted ionic liquid-dispersive microextraction and spectrophotometric determination of selenium in food samples

In the present study, a novel and eco-friendly vortex-assisted ionic liquid-based microextraction method was developed for the determination of selenium in food. The microextraction method is based on the liberation of iodine in the presence of selenium; the liberated iodine reacts with I− to form I3−. Anionic I3− reacts with cationic crystal violet dye, and the product is extracted into 1-hexyl-3-methylimidazolium hexafluorophosphate phase in the presence of Triton X-114. The proposed method is linear in the range of 2.0–70µgL−1 and has a detection limit of 9.8×10−2µgL−1. Relative standard deviations were 3.67% and 2.89% for the five replicate measurements of 14 and 35µgL−1 Se(IV), respectively. The proposed method was successfully applied to different food samples (NIST SRM 2976 mussel tissue, pepper, ginger, wheat flour, red lentil, traditional soup, cornflour, cornstarch, and garlic) after microwave digestion.

Selective determination of selenium(IV) from environmental samples by UV-visible spectrophotometry using O-methoxyphenyl thiourea as a chelating ligand

A selective extraction–spectrophotometric method has been developed for determination of selenium(IV) using O-methoxyphenyl thiourea (OMePT) as a chelating agent. The basis of the proposed method is the spectrophotometric determination of selenium(IV)–OMePT complex obtained after extraction of selenium(IV) from 3.5 M hydrochloric acid media using OMePT in chloroform solvent. The complex shows maximum absorbance at 350 nm against the reagent blank. The Beer’s law was obeyed over the concentration range 5–60 µg mL−1 of selenium(IV). The optimum concentration range was 20–50 µg mL−1 as evaluated from Ringbom’s plot. The molar absorptivity and Sandell’s sensitivity of the selenium(IV)–OMePT complex in chloroform were 3.312 × 102 L mol−1cm−1 and 0.2384 µg cm−2, respectively. The composition of selenium(IV)–OMePT complex was 1:2 established from slope ratio method, mole ratio method and Job’s continuous variation method. The complex was stable for more than 72 h. The interfering effect of various foreign ions was studied and suitable masking agents were used wherever necessary to enhance the selectivity of the developed method. The proposed method was successfully applied for the determination of selenium(IV) from real samples, viz. pharmaceutical formulations, shampoo, vegetable sample, synthetic mixtures and environmental samples. Repetition of the method was checked by finding the relative standard deviation (RSD) for 10 determinations which was 0.35%.

Solid phase spectrophotometric determination of selenium(IV) using dithisone immobilized in a polymethacrylate matrix

Solid phase spectrophotometric determination of selenium(IV) using dithisone immobilized in a polymethacrylate matrix

Flow-Batch Method with a Sequential Injection System for Spectrophotometric Determination of Selenium(IV) in Selenium-Enriched Yeast Using o-Phenylenediamine

A precise, accurate, and reliable flow-batch spectrophotometric method for the determination of selenium (IV) was developed using o-phenylenediamine as a reagent with a sequential injection monosegmented flow system incorporating a simple heating unit. The reaction zones of selenium(IV) and o-phenylenediamine were mixed and heated in a chamber at 62°C for 5 minutes. The piaselanol complexes were then detected at a maximum absorption wavelength of 335 nm. In-line single standard calibration and standard addition procedures were developed employing the monosegmented flow technique. Under the optimized conditions, a linear calibration graph in a range of 0.1–4.0 mg L−1 selenium (IV) was obtained with limits of detection and quantitation of 0.01 and 0.1 mg L−1, respectively. Relative standard deviations were 2% [for both 0.1 and 0.5 mg L−1 selenium (IV) (n = 11)]. A sample throughput of 2 h−1 using four standard addition levels was achieved. The developed system was successfully applied to raw selenium-enriched yeast samples. The analyses performed by the developed method agreed well with those obtained from a standard inductively coupled plasma mass spectrometry method.

Study on the Kinetic Spectrophotometric Determination of Selenium (IV) on Oxidation of Neutral Red with Potassium Periodate and its Application

Based on the oxidation of neutral red by KIO4 in 3.2×10-4 mol/L sulfuric acid solution, a simple kinetic spectrophotometric method was developed for the determination of trace amounts of Se(IV).The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of neutral red at 530 nm with a fixed-time method. The decrease in the absorbance of neutral red is proportional to the concentration of Se(IV) in the range 0.0–8.0 µg/L with a fixed time of 4–6 min from the initiation of the reaction. The limit of detection is 0.36 µg/L Se(IV). The influence of the factors such as acidity, concentration of reactants, reaction time, temperature and co-existing ions on the reaction is discussed. The optimum conditions of reaction are established and some kinetic parameters are determined. The apparent activation energy of catalytic reaction is 81.60 kJ/mol. The relative standard deviation for the determination of 0.1 and 0.2 µg/mL Se(IV) was 2.1 and 1.9 %, respectively. The method has been successfully applied to the determination of Se (IV) in tea and human hair samples with the relative standard deviation of 0.33 %–1.5 % and the recovery of 97.5 %–103.5 %.

Kinetic Spectrophotometric Determination of Selenium (IV) by its Catalytic Effect on the Oxidation of Acid Chrome Blue K by Hydrogen Peroxide

Based on the oxidation of acid chrome blue K (ACBK) by hydrogen peroxide in 0.002 mol/L sulfuric acid solution, while 1,10-phenanthroline (phen) acts as an activator, a simple kinetic spectrophotometric method was developed for the determination of trace amounts of Se(IV).The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of ACBK at 524 nm with a fixed-time method. The decrease in the absorbance of ACBK is proportional to the concentration of Se (IV) in the range 0.06–1.0 µg/L with a fixed time of 4–10 min from the initiation of the reaction. The limit of detection is 0.018 µg/L Se (IV). The influence of the factors such as acidity, concentration of reactants, reaction time, temperature and co-existing ions on the reaction is discussed. The optimum conditions of reaction are established and some kinetic parameters are determined. The apparent activation energy of catalytic reaction is 62.30 kJ/mol. The relative standard deviation for 11 replicate determination of 0.01 and 0.02 µg/25mL selenium (III) was calculated to be 2.3 % and 2.0 %, respectively. Combined with sulphydryl dextrane gel (SDG) separation and enriching, the method has been successfully applied to the determination of Se (IV) in foodstuff samples with the relative standard deviation of 1.1 %–3.7 % and the recovery of 99.0 %–104.0 %, the results are in good agreement with those provided by HG-AAS method.

Chemical equilibria and sequential extractive spectrophotometric determination of selenium(IV) and (VI) using the chromogenic reagent 4,4′-dichlorodithizone

The chromogenic reagent 4,4′-dichloro(3-mercapto-1,5-diphenylformazan), Cl2H2D Z , forms a yellow–red-coloured complex with selenium(IV). The produced complex species was extracted quantitatively into n-hexane, and its absorbance was measured at 416 nm. The chemical composition of the extracted selenium(IV)-Cl2H2D Z chelate and the molar absorptivity at 416 nm were found to be [SeO (Cl2HD Z )2] and 9 × 104 L mol−1 cm−1, respectively. The values of the extraction constants (K D, K ex, β) enable a convenient application of the proposed system for the liquid–liquid extraction procedure and sequential spectrophotometric determination of traces of inorganic selenium(IV) and/or selenium(VI) after reduction of the later to selenium(IV) with HCl (6 M). Beer's law and Ringbom's plots were obeyed in the concentration range 0.01–20 and 0.5–19 µg mL−1 of selenium(IV), respectively, with a relative standard deviation of 2.2%. The proposed method has been successfully applied to the determination of selenium(IV) or (VI) and total inorganic selenium(IV) and (VI) in tap and freshwater samples.

Spectrophotometric Determination of Selenium Using Potassium Iodide and Starch as Reagents

This study describes a rapid and sensitive spectrophotometric method for the determination of trace amounts of selenium, using starch and iodine as chromogenic reagents. The proposed method is based on the reaction of selenium with potassium iodide in an acidic medium to liberate iodine. This reacts with starch to form a blue colored species with an absorption maximum of 570 nm. Beer’s Law was obeyed in the range of 2–12 µg of selenium. The molar absorptivity and Sandell’s sensitivity were found to be 1.40×104 L mol−1 cm−1 and 5.45×10−3 µg cm−2 respectively. The proposed method was successfully applied to determine selenium in a sample of natural water, polluted water, soil sludge, biological samples and human hair.

Spectrophotometric determination of selenium by use of thionin.

A simple, rapid, and sensitive spectrophotometric method has been developed for the determination of selenium in real samples of water, soil, plant materials, human hair, and synthetic cosmetic and in pharmaceutical preparations. The method is based on the reaction of selenium with potassium iodide in an acidic medium to liberate iodine. The liberated iodine bleaches the violet color of thionin, and which is measured at 600 nm. This decrease in absorbance is directly proportional to selenium concentration and obeys Beer's law in the range 1-5 micro g selenium in a final volume of 10 mL (0.1-0.5 microg mL(-1)). The molar absorptivity and Sandell's sensitivity of the method were found to be 7.33 x 10(4) L mol(-1) cm(-1) and 0.0011 microg cm(-2), respectively. The optimum reaction conditions and other analytical conditions were evaluated. The effect of interfering ions on the determination is described.

Spectrophotometric Determination of Selenium in the Presence of Copper and Tellurium. Application to Anodic Slimes.

Selenite reacts with iodide ion quantitatively in acidic solution forming selenium and iodine. The iodine formed is extracted into chloroform phase and its absorbance is measured at 509 nm. With this method 10-2 -5×10-6 M selenium could be determined. The interference of copper is removed by the precipitation of its hydroxide at pH 6 - 6.5 and 10-4 M selenite could be determined with 1 - 4% relative error in the presence of 10-2 M copper and tellurium. This method is applied to anodic slime samples. The results are in accordance with the results obtained with different methods.

Spectrophotometric determination of selenium(IV) with 5,5-dimethyl-1,3-cyclohexanedione

5,5-Dimethyl-1,3-cyclohexanedione (dimedone) reacts in acid aqueous solution with selenium(IV) to give a benzoxaselenol which has an absorption maximum at 313 nm with a molar absorptivity of 4.00 × 10 3 l.mole −1.cm −1. The compound is extractable into chloroform, to give a solution with an absorption maximum at 300 nm with a molar absorptivity of 3.77 × 10 3 l.mole −1.cm −1. The calibration graph is linear up to 30 ppm selenium, with a detection limit of 0.1 ppm in the final solutions. Of the various other ions tested, only iron(III) interferes at all concentrations but the addition of 1000 ppm fluoride will mask 50 ppm Fe 3+. The method has good reproducibility, with a relative standard deviation of 1.0% for pure solutions. The method has been applied to the analysis of fire-refined copper.

The reaction of Se(IV) with 2-aminodiphenylamine and its application to spectrophotometric determination of selenium in a strongly acidic medium

Se(IV) reacts with 2-aminodiphenylamine in perchloric, sulphuric or hydrochloric acid media to give the phenylbenzoselen-adiazolium cation. The optimum hydrogen-ion concentration ranges from about 0.1 to 5M. The molar absorptivity at λ=352 nm is 1.81×104 1 · mole−1 · cm−1. The product is extracted as an ion-association complex with perchlorate into a mixture of hexanol and chlorobenzene. The kinetics of the reaction was investigated.

Spectrophotometric Determination of Selenium in Soil and Alloys

Spectrophotometric Determination of Selenium in Soil and Alloys

Spectrophotometric determination of selenium(IV) and selenium(VI)with flow injection

Spectrophotometric determination of selenium(IV) and selenium(VI)with flow injection

Spectrophotometric determination of selenium(IV) with potassium butyl xanthate

A simple, convenient and highly selective spectrophotometric method for the determination of platinum has been developed using potassium butyl xanthate. The optimum concentration range evaluated by Ringbom's method was found to be 4.87–9.75 ppm. The method of continuous variations and the molar ratio method confirmed a platinum to reagent ratio of 1 : 3 in the complex. The effect of pH, excess of reagent and foreign ions on the determination of platinum(IV) and the effect of time, temperature and the solubility of the complex with various solvents were studied.

Spectrophotometric determination of selenium with dithizone

Microgram amounts of selenium(IV) are determined by measuring the decrease in absorbance of dithizone in carbon tetrachloride solution at 620 nm. Relative standard deviations for samples containing 0.20 and 1.00 μg of selenium(IV) are 0.6% and 0.4%, respectively. Of several metals tested only copper (at the 1.0-μg level) and iron (at the 100-μg level) interfere but high concentrations of nitric or perchloric acid cause low results. A reinvestigation of the reaction of selenium(IV) with dithizone suggests a formula Se(HDz) 4 for the dithizonate.

Round robin tests on the spectrophotometric determination of selenium by a modified 3, 3'-diaminobenzidine method

Round robin tests on the spectrophotometric determination of selenium by a modified 3, 3'-diaminobenzidine method

Spectrophotometric determination of selenium in concentrates and high-purity copper metal with 3,3′-diaminobenzidine after separation by xanthate extraction

A method for determining 0.0001–0.10% of selenium in copper, nickel, molybdenum, lead and zinc sulphide concentrates is described. After sample decomposition, selenium is reduced to the quadrivalent state by heating in a 4 M hydrochloric acid-5 M sulphuric acid medium, then extracted into chloroform as the xanthate, and ultimately determined spectrophotometrically with 3,3′-diaminobenzidine. Small amounts of iron, lead and copper, and an appreciable amount of molybdenum are co-extracted as xanthates but do not interfere. More than 5 mg of antimony will cause low results. The proposed method was developed primarily for concentrates, but it is also applicable to high-purity copper.