Determination Of SE(IV) in the Presence of SE(VI) at NG ML− Concentration Levels by a Kinetic Spectrophotometric Method

ABSTRACT

The catalytic effect of Se(IV) on the reduction reaction of thionine(TN) by sulfide ion is used for determination of trace amounts of selenium(IV) ion by a kinetic-spectrophotometric method. This new method is simple and highly sensitive. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of the reaction mixture at 598 nm. The fixed time method was used for the first 45s from initiation of the reaction. Under the optimum conditions, in the concentration range of 2-90 ng ml^? of selenium(IV), a quite linear regression equation (r = 0.9984, n = 14) was obtained. The experimental detection limit of the method (S/N = 3) was 1.3 ng ml^?. The relative standard deviation of ten replicate measurements is 2.51% for a 40 ng ml^? solution of selenium. The proposed method is used to the study of selenium (IV,VI) speciation in water at ng ml^? levels. This method was extended for the determination of selenium in real samples.     

Spectrophotometric Catalytic Determination of Trace Amounts of Selenium Based on the Reduction of Azurea by Sulphide

ABSTRACT

A sensitive catalytic kinetic spectrophotometric method for determining ng ml^?1 concentrations of selenium is described. The method, based on the catalytic effect of Se (IV) on the reduction of azureA by sulphide, is monitored spectrophotometrically at 600 nm. The linearity range of the calibration graph is dependent on the concentration of sulphide. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. The method is simple, rapid, precise, sensitive, free from many interferences and is widely applicable. The limit of detection is 2.5ng ml^?1 of Se. The relative standard deviation of seven determinations of 100 ng ml^?1 Se was 1.5%. The method was applied to the determination of selenium in spiked water, Kjeldahl tablets, synthetic samples and health care products.     

A new reagent system for the highly sensitive spectrophotometric determination of selenium

Highly sensitive and simple spectrophotometric determination of selenium is described for the determination of selenium(IV) using a new reagent leuco malachite green. The method is based on the reaction of selenium(IV) with potassium iodide in an acidic condition to liberate iodine, the liberated iodine oxidizes leuco malachite green to malachite green dye. The green coloration was developed in an acetate buffer (pH 4.2–4.9) on heating in a water bath (∼ 40 °C). The formed dye exhibits an absorption maximum at 615 nm. The method obeys Beer’s law over a concentration range of 0.04–0.4 μg mL⁻¹ selenium. The molar absorptivity and Sandell’s sensitivity of the color system were found to be 1.67 × 10⁵ L mol⁻¹ cm-¹ and 0.5 ng cm⁻², respectively. The optimum reaction conditions and other analytical parameters have been evaluated. The proposed procedure has been successfully applied to the determination of selenium in real samples of water, soil, plant material, human hair, and cosmetic samples. The results were compared to those obtained with the reference method. Statistical analysis of the results confirms the precision and accuracy of the proposed method. In addition, the developed method is cost-effective and involves easily accessible instrumentation technique which can be used by ordinary research laboratories.     

A facile spectrophotometric method for the determination of selenium.

A rapid and sensitive spectrophotometric method is described for the determination of trace amounts of selenium using Variamine Blue (VB) as a chromogenic reagent. The proposed method is based on the reaction of selenium with potassium iodide in an acidic medium to liberate iodine, which oxidizes Variamine Blue to form a violet-colored species having an absorption maximum at 546 nm. Beer's law is obeyed in the range 2-20 g of selenium in a final volume of 10 ml. The molar absorptivity and Sandell's sensitivity were found to be 2.6 x 10(4) l mol-1 cm-1 and 0.003 microgram cm-2, respectively. The optimum reaction conditions and other analytical parameters were evaluated. The effect of interfering ions on the determination is described. The proposed method has been successfully applied to the determination of selenium in real samples of water, soil, plant materials, human hair, and synthetic samples of cosmetics and pharmaceutical preparations.     

Spectrophotometric catalytic determination of ultra-trace amounts of selenium based on the reduction of resazurin by sulphide

A sensitive catalytic method for determining ng ml^? concentration of selenium is described. The method is based on the catalytic action of Se(IV) on the reduction of resazurin by sulphide, monitored spectrophotometrically at 605 nm. The linearity range of the calibration graph is dependent on the concentration of sulphide. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. The method is simple, rapid, precise, sensitive and widely applicable. As low as 8.0 × 10^?4 μg ml^?1 of selenium can be determined. The relative standard deviation of seven determination of 10 ng Se was 0.7%. The determination of Se(IV) in the presence of Se(VI) and the determination of total selenium are also described.     

Catalytic Kinetic Determination of Trace Amounts of Copper with Polarographic Detection

Abstract

This method is based on the catalytic effect of copper(II) on the redox reaction between acid chrome dark blue and ascorbic acid in acetic acid-sodium acetate buffer solution and 1,10-phenanthroline as an activator. Acid chrome dark blue exhibits a sensitive polarographic wave at -0.375V Vs. SCE and change of acid chrome dark blue concentration is traced by a polarographic detection technique. The detection limit and the linear range of copper(II) are 2.34ng/ml and 5 to 50ng/ml respectively. This new catalytic method has been applied to the determination of copper in human hair, with satisfactory results.     

应用巯基棉富集分离催化光度法测定发硒含量的研究

通过巯基棉对经预处理的发硒富集分离，然后用催化光度法测定，方法简单，操作方便，灵敏度高，适于临床检验用。     

Ultraviolet Spectrophotometric Determination of Selenium by 1-Pyrrolidinecarbodithioate Method

Abstract

An ultraviolet spectrophotometric method for the determination of selenium has been developed using ammonium 1-pyrrolidinecarbo-dithioate. The selenium(IV)-1-pyrrolidinecarbodithioate complex is extracted with chloroform and the absorbance of the extract measured at 303 mμ. Conformity to Beer's law was found for 0.5 to 9 ppm of selenium.     

Determination of trace selenium in human plasma and hair with ternary inclusion compound-fluorescent spectrophotometry

A method for determination of selenium in plasma and hair with ternary inclusion compound-fluorescent spectrophotometry has been developed. The determination of selenium in plasma and hair can be performed directly in aqueous solution. Blood and hair samples were destroyed by oxygen flask combustion. The linear range was 10-500 ng mL-1 for plasma and 10-100 ng mL-1 for hair. Within-day and day-to-day precisions for plasma ranged from 5.4% to 9.3% (n = 7) and from 3.5% to 14.5% (n = 7), respectively. Within-day precisions for hair ranged from 0.6% to 6.2% (n = 7). Recoveries ranged from 91.0% to 97.8% for plasma and from 95.0% to 102.0% for hair. The blood samples from 15 Hans and 20 Uygurs in Xinjiang Uygur automatic region and 23 Hans in Liaoning province were collected and determined. It was indicated that no statistically significant difference in plasma selenium concentration of the Hans between Xinjiang and Liaoning was found (F = 1.36, P > 0.05). However, there were statistically significant differences between the Hans and the Uygurs in Xinjiang (F = 1.01, P < 0.01) and between males and females in the two areas (P < 0.01). There was a low correlation between plasma selenium concentration and hair selenium concentration. The ratio of hair selenium concentration to plasma selenium concentration was 2.17, with a range of 1.63-2.88.     

Coprecipitative Preconcentration and Differential Pulse Cathodic Stripping Voltammetric Determination of Selenium (IV)

Abstract

A DPCSV procedure for the determination of selenium (IV) with a prior preconcentrative coprecipitation on iron (III) hydroxide has been developed. The experimental conditions for coprecipitation of selenium (IV) onto iron (III) hydroxide, viz. pH, iron (III) concentration, volume of aqueous phase and selenium concentration, were optimized. The coprecipitated selenium (IV) is dissolved in 10 ml of 0.1 M HCl and analysed using DPCSV in the presence of copper (II). Selenium concentrations as low as 10–100 ng present in 500 ml of the aqueous phase could be determined. The method is precise and has been applied to the analysis of sea water and reference material samples.     

A visual test method for determining selenium(IV) with indigocarmine immobilized on silica

A solid reagent based on silica successively modified by quaternary ammonium salt and indigocarmine is proposed for the test determination of selenium(IV). The detection limit for selenium is found to be 10 μg/L using catalytic reaction of the reduction of immobilized indigocarmine by sulfide as an indicator reaction. The calibration graph is linear in the range of selenium concentrations from 50 to 400 μg/L. Alkali and alkaline-earth metals, NH ₄ ⁺ , Cl^?, NO ₃ ^? , and SO ₄ ^2? do not interfere with the determination of selenium. The interference from heavy metals is eliminated by introducing EDTA. The procedure was tested in determining selenium in preparations of vitamins and biologically active supplement.     

Catalytic Spectrophotometric Determination of Nanogram Amounts of Selenium(IV)

A method is proposed for the catalytic spectrophotometric determination of nanogram amounts of selenium(IV). The method is based on the reduction of nitrate with iron(II) ethylenediaminetetraacetate catalyzed by Se(IV) compounds. The reaction proceeds in several stages and yields iron(III) ethylenediaminetetraacetate, the nitrosyl complex of iron, nitrous acid, and other products. Nitrous acid enters into the diazotization reaction with aromatic amine. The resulting diazo compound is coupled with another aromatic amine to form the azo compound. 4-Nitroaniline is used as the diazo component, and N-diethyl-N-(1-naphthyl)ethylenediamine is used as the azo component. The molar absorptivity of the solution of the azo compound is 4.5 × 10⁴ at 540 nm. A kinetic method was developed for the determination of selenium(IV) in potable and natural waters with the use of the standard addition method. The detection limit of selenium by the proposed method is 0.1 ng/mL. In the determination of 0.2 and 2 ng/mL selenium, the relative standard deviation is 6 and 2%, respectively. The interfering effect of organic compounds dissolved in natural water is eliminated by the ultrasonic treatment of water samples.     

Comparison of selenium content in human hair from different individuals in different countries,by76Se(n,γ)77mSe reaction

Samples of hair from 370 subjects were analysed by neutron activation. The samples were taken from residents of nine different countries: Japan, France, Ivory Coast, Brasil, Paraguay, Canary Islands, Papua New Guinea, Italy and New Zealand. The selenium determination was made using the⁷⁶Se(n,)^77mSe reaction.It was found that the average selenium concentration in the hair of Japanese subjects, both those living in Japan and those living in foreign countries was higher (total average: 0.59±0.14 mg/kg) than those of subjects from other countries (total average: 0.42±0.13 mg/kg).Our results from the determination of the selenium concentration in the hair of individuals from different countries show significant differences between different countries, nevertheless, the selenium content in human hair was small amounts. Since this is likely due to differences in diet. This method was able to analyze quickly for many samples.     

Determination of Hemin using a Parallel Catalytic Reduction Wave of its Protoporphyrin IX Ring

Abstract

Hemin, iron (III) protoporphyrin IX chloride, in NH₃‐NH₄Cl buffer solution of pH 9.5 produces an insensitive reduction wave at about ?0.70 V (vs. saturated calomel reference electrode, SCE) by using single sweep polarography. Adding oxidant K₂S₂O₈ to the solution, hemin reduction wave is catalyzed, yielding a parallel catalytic wave. The catalytic current is 20 times of hemin original reduction current. The derivative peak height is linearly proportional to the hemin concentration in the range of 7.5×10^?8 to 4.5×10^?6 mol/l, the detection limit is 5.0×10^?8 mol/l. Serum albumin, common amino acids, and metal ions have no interference with the hemin determination. The proposed method has been applied to the determination of hemin content in oral liquid samples with satisfactory results. The parallel catalytic wave is attributed to the catalytic reduction of porphyrin ring of hemin at the dropping mercury electrode. The new method could be useful in biochemical, clinical, and pharmaceutical analysis.     

The use of electrothermal vaporization ICP-OES for the determination of trace elements in human hair using slurry sampling and PTFE as modifier

A procedure for the determination of trace elements in human hair has been proposed by electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) with slurry sampling. Slurry was prepared by immersing human hair with conc. HNO₃ and then adding a polytetrafluoroethylene (PTFE) slurry, which was used as a chemical modifier for the improvement of vaporization characteristic of analyte. The slurry was homogenized with an ultrasonic vibrator before the measurement. The vaporization behaviour of the analytes in slurry and solution and the main influence factors for the determination were studied with the addition of PTFE systematically. Detection limits for this method varied from 0.033?µg?g^?1 (Cu) to 3.21?µg?g^?1 (Zn) with the relative standard deviations (RSDs) of 2.8–7.1%. The proposed method was successfully applied for the determination of trace elements (Cu, Mn, Cr, Fe, Zn, Cd and Pb) in human hair with minimum chemical pretreatment and aqueous calibration. The accuracy was checked by comparing the results of this method with those using pneumatic nebulization (PN) ICP-OES after a conventional acid decomposition of the same sample. In addition, the standard reference material of human hair (GBW 07601) was analysed with good agreement between the results from the proposed method and the certified values.     

Studies on Mercury Pollution: Microdetermination of Mercury in Biological Materials by Cold Vapour Atomic Absorption Spectrometry

Abstract

A simple, rapid, precise and accurate method for the determination of mercury in biological material is described. Biological samples were digested with nitric acid and acidified potassium permanganate and determined by cold vapour analyser. The proposed method was successfully employed for the determination of mercury in samples of fish, hair and blood.     

催化动力学法测定人发中痕量硒

催化动力学褪色法测定痕量硒已有报道[1 ,2 ] ,但大都存在Ｆｅ3+、Ｃｕ2 +等共存离子的干扰。在实际分析中常需对样品进行繁琐的预处理。实验研究了在盐酸溶液中 ,以ＥＤＴＡ作掩蔽剂 ,痕量硒催化氯酸钾氧化 5 Ｂｒ ＰＡＤＡＰ褪色反应及其动力学条件 ,以加硒催化反应与不加硒非催化反应的吸光度之差△Ａ对温度 1 /Ｔ作图得一直线 ,由Ａｒｒｈｅｎｉｕｓ式求得该反应的活化能Ｅａ=94ｋＪ/ｍｏｌ,建立了测定硒的新方法。方法检测限为 5.7× 1 0 - 5μｇ/ｍｌ,Ｓｅ(Ⅳ)的测定范围为 0～ 0 .4μｇ/ 2 5ｍｌ,用此法测定人发中痕量硒 ,结果令人满…     

Kinetic Flow Injection Spectrophotometric Determination of Nitrite by its Catalytic Effect on the Oxidation of Chlorophosphonazo-pN by Bromate

Abstract

A flow injection kinetic method has been developed for the determination of nitrite, based on its catalytic effect on bromate oxidation of chlorophosphonazo-pN in H₂SO₄ medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance at 551 nm. The sampling frequency was 83 h^?1. The calibration curve was linear between 0.050 and 1.00 μg/ml, and the detection limit was 0.018 μg/ml. The proposed method was applied to the determination of nitrite in waters and soil with satisfactory results.     

Kinetic Spectrophotometric Determination of Traces of Manganese(II) by Its Catalytic Effect on Oxidation of 4‐Hydroxycoumarin with Potassium Permanganate in River Water Samples

Abstract

A new kinetic method for determination of traces of manganese(II) based on its catalytic effect on the oxidation of 4‐hydroxycoumarine with KMnO₄ at pH=1.35 and at a temperature of 25°C was proposed. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 525 nm. The calibration graph is linear in the range 20–200 ng/cm³. The effects of certain foreign ions upon the reaction rate were determined for assessment by the selectivity of the method. The proposed method has been applied for determination of manganese(II) in river water samples with satisfactory results.