The nephelometric determination of selenium with 2,3-diaminonaphthalene

A nephelometric determination of selenium has been developed in the concentration range from 10 to 300 ppm based on the reaction of Se(IV) with 2,3-diaminonaphthalene. The method is inexpensive, simple, and requires little operator time or skill.     

A critical evaluation of fluorometric methods for determination of selenium in plant materials with 2,3-diaminonaphthalene

The published methods for fluorometric determination of Se in plants are reviewed, with particular attention to those using 2,3-diaminonaphthalene as the fluorometric reagent. Two steps in the analysis are shown to be critical: the final stages of the digestion and the complete conversion of the Se to Se(IV). A modified experimental procedure is given.     

Modification of the methylene blue method for spectrophotometric selenium determination

The spectrophotometric method for Se(IV) determination based on its catalytic effect in the reduction of Methylene Blue (MB) by sulphide is modified. The variables that affect the decolorization of MB were taken into account: reagent concentrations, order of addition, mixing and standing times, pH, ionic strength, temperature, solution volume, wavelength, etc. The results of this study allowed a decrease of the determination limit and, by selection of the appropriate analytical conditions, choice of optimum linear range according to the selenium content in the sample. The lower limit range is 15-75 mug/1., with 3% relative standard deviation and no systematic errors. Procedures for overcoming several potential interferences were studied. The proposed method was applied to several environmental samples and the results were compared with those obtained by other standard methods.     

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.     

Kinetic spectrophotometric method for simultaneous determination of selenium and tellurium using partial least squares calibration

A kinetic-spectrophotometric method for the simultaneous determination of Se(IV) and Te(IV) is described. The method is based upon the catalytic effect of these cations on the reaction of toluidine blue with sulfide. Partial least squares calibration method was employed for the data manipulation and analysis. The concentrations were varied between 0.02-0.24 and 0.01-0.08 μg/ml for Se(IV) and Te(IV), respectively. Cross-validation method was used to select the optimum number of factors (NF). The root mean square errors of difference for selenium and tellurium were 1.2 and 1.7 μg/ml, respectively. Application of the method to artificial samples and several mixtures of standard solutions of Se(IV) and Te(IV) were performed and satisfactory results were obtained.     

Rapid determination of trace amounts of selenium (IV), nitrite, and nitrate by high-pressure liquid chromatography using 2,3-diaminonaphthalene

Selenite, nitrite, and nitrate ions have been determined spectrophotometrically and fluorometrically using the reagent 2,3-diaminonaphthalene and high-pressure liquid chromatography. A fluorometric detector was constructed for the HPLC systems. The developed procedures were applied to the analysis of water and biological materials.     

Chemometrics-assisted spectrophotometric method for simultaneous determination of vitamins in complex mixtures

An advanced independent component analysis algorithm (MILCA) is applied for simultaneous chemometric determination of fat- and water-soluble vitamins in complex mixtures. The analysis is based on the decomposition of spectra of multicomponent mixtures in the UV region. The key features of the proposed method are simplicity, accuracy, and reliability. Comparisons between the new algorithm and other established methods (MCR-ALS, SIMPLISMA, other ICA techniques) were made. Our results indicate that in most cases, MILCA is comparable or even outperforms other chemometrics methods taken for comparisons. The influence of different factors (abundance of components, noise, step of spectral scan, and scan speed) on decomposition performance has been investigated. The optimal conditions for spectroscopic registration have been identified. The proposed method was used for analysis of model mixtures and real objects (multivitamin drugs, food additives, and energy drinks). The resolved concentrations match well with the declared amounts and the results of reference methods.     

A new spectrophotometric method for the determination of hydrazine in environmental samples

Summary Hydrazine is determined spectrophotometrically by using veratraldehyde (3,4-dimethoxybenzaldehyde) as a new reagent. The reaction is based on the condensation of veratraldehyde with hydrazine in acidic medium. The resulting yellow coloured condensation product has maximum absorption at 410 nm. The colour system obeys Beer's law in the range of 0.065 to 0.3 g/ml of hydrazine. Molar absorptivity and Sandell's sensitivity are found to be 6.72×10⁴ l mol^–1 cm^–1 (±100) and 0.0004 g cm^–2, respectively. The method is successfully applied for the determination of hydrazine in polluted water, biological samples, in isoniazide tablets and in air. It is compared with other reported spectrophotometric methods and is found to be of comparable sensitivity.     

Modified spectrophotometric method for the determination of traces of boron using quinalizarin in a sulfuric-acetic acid medium

Summary A modified spectrophotometric method for the determination of boron with quinalizarin in a sulfuric-acetic acid medium is proposed. The sensitivity of the method is 0.00037g/cm². The optimum concentration range is 0.06 to 0.25 ppm of boron.

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Zusammenfassung Eine modifizierte spektrophotometrische Bestimmungsmethode für Bor mit Chinalizarin in schwefelsaurer-essigsaurer Lösung wurde vorgeschlagen. Deren Empfindlichkeit beträgt 0,00037g/cm². Das optimale Konzentrationsbereich liegt zwischen 0,01 und 0,25 ppm Bor.

     

Automatic spectrophotometric method for the determination of europium in mixtures with yttrium and other lanthanides

Summary An automatic spectrophotometric method for the determination of europium in the presence of yttrium and other lanthanides is described. The method is based on a modification of a recently devised manual procedure consisting of the reduction, on a Jones reductor, of europium(III) to europium(II) which is used to reduce molybdophosphate to a molybdenum blue. The method is capable of analysing solutions containing 10–400 g of europium per ml at a rate of 20 samples per hour. There is no interference from yttrium or other lanthanides and the method is suitable for application to europium determination after a group separation. When applied to mineral samples coefficients of variation between 2.5 and 3.8% were obtained.

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Automatisches spektralphotometrisches Verfahren zur Bestimmung von Europium im Gemisch mit Yttrium und anderen Lanthaniden

Zusammenfassung Das Verfahren stellt eine Modifikation eines kürzlich ausgearbeiteten manuellen Verfahrens dar, das auf Reduktion (Jones Reduktor) zu Eu(II) und Reaktion mit Molybdophosphat zu Molybdänblau beruht. 20 Proben mit 10–400 g Eu/ml können je Stunde analysiert werden. Yttrium und andere Lanthanide stören nicht. Die Molybdänblaureaktion störende Substanzen können zuvor durch eine Gruppentrennung beseitigt werden. Bei der Analyse von mineralischen Proben wurden Variationskoeffizienten zwischen 2,5 und 3,8% erhalten.

     

A simple method for the spectrophotometric determination of atrazine using p-aminoacetophenone and its application in environmental and biological samples

A spectrophotometric method is described for the determination of the widely used herbicide, atrazine. Atrazine reacts with pyridine and forms a quaternary halide which adds a hydroxyl group in the presence of alkali to form a carbinol base. The heterocyclic ring of the resulting carbinol breaks forming a glutaconic dialdehyde which is subsequently coupled with p-aminoacetophenone (PMP) to form a yellow orange polymethine dye. Beer's law is obeyed in the range 0.16–1.6 ppm of atrazine at 470 nm. The method is sensitive and free from the interference of most of the foreign species. The analytical parameters have been optimised and the method has been successfully applied to the determination of atrazine in various environmental and biological samples.     

Micellanized spectrophotometric method for the determination of beryllium using haematoxylin

A simple and sensitized spectrophotometric method for the determination of trace amounts of beryllium has been described. The method is based on the formation of a ternary complex by the reaction of beryllium with haematoxylin in the presence of micellar medium (cationic surfactant, cetyltrimethylammonium bromide). The ternary complex of beryllium has a maximum absorbance at 592 nm and showed an excellent sensitivity (molar absorption coefficient of 7.07 x 10(4)L mol(-1)cm(-1) and the Sandell's sensitivity being 1.27 x 10(-4) microg cm(-2)) and reproducibility (within-day precision: R.S.D.相似文献   

Extraction spectrophotometric determination of selenium(IV) with J acid in environmental samples

A new simple and sensitive method for the extraction and spectrophotometric determination of selenium(IV) is described. Selenium(IV) is reacted with J acid (6-ANSA) to form a butanol extractable complex with maximum absorbance of 520 nm. Beer's law is obeyed in the range of 0.03-0.3 mg/l. of selenium. Molar absorptivity and Sandell's sensitivity are found to be 18.5 +/- (0.1) x 10(3) l. mol(-1). cm(-1) and 0.004 microg/cm(2), respectively. The analytical parameters were optimized and the method applied for the determination of selenium in polluted water, soil, dust, hair and plant materials. The method is compared with other reported methods and found to be superior to many of the reported methods.     

Simultaneous determination and validation of some binary mixtures of antihypertensive drugs using ratio derivative spectrophotometric method

Ratio derivative spectrophotometric technique is presented for the rapid, accurate and precise simultaneous determination of olmesartan medoxomil (OLM), hydrochlorothiazide (HCT), and zofenopril (ZOF) as well as HCT binary mixtures in their dosage forms. First derivative of the ratio spectra (DD1) by measurements using different amplitudes was used and calibration graphs were established for 0.5–12 mg/mL HCT and 0.5–20 mg/mL OLM and ZOF. This method depends on first derivative of the ratio spectra by division of the absorption spectrum of the binary mixture by a standard spectrum of one of the components and then calculating the first derivative of the ratio spectrum. The first derivative of the ratio amplitudes at 250.4 and 291.5 nm for OLM, 250.4 and 298.1 nm for ZOF and 231.8, 332.2, 232.3 and 280.4 nm for HCT were selected for the determination. The proposed methods were successfully applied for determining of both drug combinations (ZOF-HCT and OLM-HCT) in their synthetic mixtures and in pharmaceutical dosage forms. The described procedures are extensively validated, non-destructive and do not require any separation steps.     

紫外分光光度法测定硒氧化过程中二氧化硒

利用5-硝基-2,1,3-苯并苤硒脑对紫外光的吸收特性,用紫外分光光度计测定硒氧化过程中硒(Ⅳ)含量。研究了硒(Ⅳ)与4-硝基邻苯二胺(NPDA)生成5-硝基-2,1,3-苯并苤硒脑的衍生反应条件,验证了测定结果的准确性。结果表明:衍生反应适宜条件为pH2,反应温度60℃,反应时间10 min,NPDA试剂用量为硒(Ⅳ)的168倍。在0.002~0.02 g/L硒(Ⅳ)范围内,硒(Ⅳ)浓度与衍生产物5-硝基-2,1,3-苯并苤硒脑的吸光度线性关系良好。用该法测定硒氧化过程中二氧化硒含量,RSD为0.52%。硒(Ⅳ)的平均加标回收率为98.12%。本文建立的紫外分光光度法为硒含量较大的体系中硒(Ⅳ)定量分析提供了准确、便捷的测定方法,对于其它价态硒(Ⅵ价、Ⅱ价、0价)测定有借鉴作用。     

两相体系分光光度法测定聚乙二醇化蛋白质混合物中游离聚乙二醇

建立了用硫氰酸铁胺-氯仿两相体系分光光度法测定游离聚乙二醇含量的方法。确定了最大吸收波长，考察了混合振荡时间、其他生物大分子存在对测定结果的影响，并与三硝基苯磺酸(TNBS法)进行了比较。     

A new reagent for determining trace selenium by gas chromatography: 1,4-dibromo-2,3-diaminonaphthalene

1,4-Dibromo-2,3-diaminonaphthalene is proposed as a reagent for conversion of selenium into a piazselenol, for determination by gas chromatography. The limit of detection is 0.03 ng of selenium.