Spectrophotometric determination of traces of silicon as molybdenum blue in uranium dioxide

Summary A procedure for the determination of small amounts of silicon in uranium dioxide is described. Silicon is determined directly in the sample solution by means of the molybdenum blue method with 1-amino-2-naphthol-4 sulphonic acid as a reducing agent. Contents down to 5 ppm can be determined with an error not exceeding ±5%.

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Spektrophotometrische Bestimmung von Siliciumspuren als Molybdänblau in Urandioxid

Zusammenfassung Silicium wird direkt in der Probelösung als Molybdänblau nach Reduktion mit 1-Amino-2-naphtholsulfonsäure-(4) bestimmt. Siliciumgehalte bis herab zu 5 ppm können mit einem Fehler von höchstens ±5% bestimmt werden.

     

Spectrophotometric and fluorometric determination of cobalt

The reaction of Co(II), pyridine-2-aldehyde-2-pyridyl hydrazone (PAPHY) and eosin at pH 5.6 produces the ternary complex Co(L)(HL)E(2) (where HL represents the protonated form of the ligand and E represents the eosinate anion). This complex is extracted by a chloroform-acetone mixture to give a strongly coloured and highly fluorescent extract. Spectrophotometric and fluorometric methods for the determination of Co have been developed with detection limits of 0.017 and 0.008 ppm respectively. Cu(II), Ni, Fe(II), Pd(II) and Hg(II) interfere. The Spectrophotometric method has been successfully applied to the analysis of steels, following ion-exchange separation of Co.     

Spectrophotometric determination of traces of arsenic

Arsenic(III) is extracted into carbon tetrachloride from 3.5M sulphuric acid that is 0.8M in potassium iodide. 8-Mercaptoquinoline and acetone are added to the organic extract and the absorbance of the arsenic(III)-8-mercaptoquinolinate formed is measured at 380 nm. Repeating the extraction procedure highly increases the selectivity of the method; only tin(II) interferes with the determination.     

Spectrophotometric determination of traces of antimony

Antimony(III) is extracted into carbon tetrachloride from 4M sulphuric acid that is 0.05M in potassium iodide. 8-Mercaptoquinoline and acetone are added to the organic extract and the absorbance of the complex formed is measured at 390 nm. Repeating the extraction procedure greatly increases the selectivity of the method.     

Spectrophotometric determination of traces of formaldehyde

Summary A comparative study of various colorimetric methods for determining and detecting traces of formaldehyde has been made. Chromotropic acid and 2,7-duiydroxynaphthalene were found to be the best reagents and were subjected to a thorough study. Precise and accurate methods for determining formaldehyde using either chromotropic acid or 2,7-dihydroxynaphthalene are described. The color system produced by following the standard procedure obeys Beer's law. Using chromotropic acid 0.05 g to 2.0 g of formaldehyde per ml can be determined quite accurately. Acrolein seems to be the only seriously interfering substance, and its interference can be much diminished by slightly modifying the standard procedure. The reagent solutions are perfectly stable.     

Spectrophotometric determination of trace molybdenum in plants and seeds with 3,5-dibromo-4-hydroxyphenylflurone

A novel spectrophotometric method based on a new reagent, 3,5-dibromo-4-hydroxyphenylflurone, was developed for the determination of molybdenum in plants and seeds. 3,5-Dibromo-4-hydroxyphenylflurone showed outstanding analytical characteristics for spectrophotometric determination of molybdenum. The reaction conditions are simple and stable. In 0.2 mol l(-1) phosphoric acid medium (which can combine with iron and other metal ions and greatly improves the selectivity of the color system), molybdenum(VI) reacts with 3,5-dibromo-4-hydroxyphenylflurone to form a 1:2 red complex with an absorption maximum at 530 nm, the color reaction can completed in 2 min and the absorbance of the molybdenum complex remains stable for at least 72 h at room temperature. Its stability constant is 1.21 x 10(28) at 25 degrees C. Beer's law is obeyed over the range 0-0.6 microg ml(-1) Mo(VI). The reagent has very high sensitivity and selectivity; the molar absorptivity of the complex is 1.35 x 10(5) 1 mol(-1) cm(-1) and the limit of quantification, the limit of detection and relative standard deviation (n = 10) were found to be 6.7 ng ml(-1), 2.2 ng ml(-1) and 1.01%, respectively. Cu (50000-fold), Fe (20000-fold), K (20000-fold), NH4+ (20000-fold), Mg (15000-fold), Zn (10000-fold), Na (10000-fold), Al (4000-fold), Ca (25000-fold), Mn (2000-fold), Ce (500-fold), Cr (400-fold) and Bi (200-fold) do not interfere with the determination of trace levels of molybdenum up to the excesses indicated. The selectivity is much superior to that of other published methods. The proposed method was applied to the direct determination of molybdenum in plants and seeds with satisfactory results. The synthesis of the reagent and conditions of color reaction were studied in detail.     

Spectrophotometric determination of traces of oxygen in water

Winkler's method of determining oxygen in water by titration of the iodine can not be applied with concentrations below 0.03 mg O₂/litre. We studied the spectrophotometric determination of the iodine-starch complex described by bairstow, francis, and wyatt and succeeded in improving its stability by the addition of potassium sulphate. The intensity of the blue colour is very sensitive to variation of temperature. Below 10° C this influence can be neglected. Upwards from 30° C the intensity rapidly decreases. Instead of performing the determination at 10° C we plotted the extinction coefficient of dilute solutions as a function of the iodine concentration for temperatures ranging from 10 to 30° C. With “the aid of this graph the iodine concentration can be found when the extinction coefficient and the temperature of a solution are determined.With this method we can determine oxygen in water in concentrations ranging from 0.005 to 0.4 mg O₂/litre. Duplicates (for water with a low content of oxygen) differ not more than 0.002 mg O2/litre.     

Spectrophotometric determination of microquantities of molybdenum

Summary A new spectrophotometric method for the determination of microquantities of molybdenum (VI) and rutin, respectively, has been described. In order to take all the advantages of this very sensitive method, the effect of some foreign ions on these determinations has been studied and a combined chromatographic-spectrophotometric procedure for the separation and the determination of microamounts of molybdenum (VI) in the presence of a large number of interfering ions has been developed.

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Spektrophotometrische Bestimmung von Mikromengen Molybdän

Zusammenfassung Eine neue spektralphotometrische Methode zur Bestimmung von Mikromengen von Molybdän(VI) bzw. von Rutin wurde beschrieben und der Einfluß einiger Fremdionen auf diese Bestimmung untersucht. Um die Anwendungsmöglichkeiten dieser Methode zu erweitern, wurde ein kombiniertes chromatographisch-spektrophotometrisches Verfahren zur Abtrennung und Bestimmung von Mikromengen Molybdän(VI) in Gegenwart einer größeren Zahl störender Ionen ausgearbeitet.

     

Spectrophotometric determination of molybdenum with phenylfluorone

Spectrophotometric studies on the reaction between molybdenum as molybdate (MoO₄^2?) and phenylfluorone are presented. The reaction conditions are optimized to develop an intense color (molar absorptivity is 3.8 × 10³) selective and sensitive for the Spectrophotometric determination of molybdenum. The absorbance is measured at 560 nm, at a pH of 1.5–3. The colored complex is stable for up to 24 hr, Beer's law is obeyed, over the concentration range of 1 to 4 μg/25 ml. The relative standard deviation is 2% and the sensitivity of the method is 1.60 × 10^?4 mg/ml.     

Spectrophotometric determination of molybdenum with lobeline

Lobeline hydrochloride has been tested as a reagent for molybdenum(V). Molybdenum(VI) is reduced with hydrazine sulfate in hydrochloric acid solution to Mo(V) only and complexed with thiocyanate and lobeline which is extracted with chloroform. In the paper experimental conditions for the formation of the ion pair of lobeline with molybdenum thiocyanate are described and the composition of this complex is given.     

Field determination of molybdenum in soils

A new procedure for the field characterization of the available amount of molybdenum in soil extract is described. It is based on the preconcentration of the Mo(V)-SCN^– complex into toluene solution of N-octylacetamide (OAA) and subsequent heating of the extract for ≈ 10 min at 60° C over a water bath. The molar absorptivity of the complex is (3.50) × 10⁴ 1 mole^–1 cm^–1 at λ_max 470 nm. The detection limit of the method is 4 ppb Mo. It provides a significantly increased tolerance limit for iron (up to 1000 ppm) and is applicable to the field characterization of Mo in soil extracts. Received: 29 May 1996 / Revised: 17 July 1996 / Accepted: 19 July 1996     

Field determination of molybdenum in soils

A new procedure for the field characterization of the available amount of molybdenum in soil extract is described. It is based on the preconcentration of the Mo(V)-SCN⁻ complex into toluene solution of N-octylacetamide (OAA) and subsequent heating of the extract for ≈ 10 min at 60° C over a water bath. The molar absorptivity of the complex is (3.50) × 10⁴ 1 mole^-1 cm^-1 at λ_max 470 nm. The detection limit of the method is 4 ppb Mo. It provides a significantly increased tolerance limit for iron (up to 1000 ppm) and is applicable to the field characterization of Mo in soil extracts.     

Spectrophotometric molybdenum determination with thiolactic acid

A quick, selective method for molybdenum(VI) is based on the formation of a yellow thiolactic acid complex. The complex is formed at pH 1.0-1.6, and the absorbance is measured at 365 nm.     

Spectrophotometric determination of traces of selenium with diaminobenzidine

Diaminobenzidine is suitable for the spectrophotometric determination of traces of selenium. The reaction is very sensitive, the molecular extinction coefficient being as high as 10,200. The reaction is specific, the most common ions causing no perturbation. The procedure is especially valuable for the determination of traces selenium in tellurium and in sulfur, provided that the latter is present in the sulfate form.     

Spectrophotometric determination of molybdenum in rocks with thiocyanate

A rapid procedure for the determination of microgram amounts of molybdenum in rocks is described. After acid decomposition, molybdenum is extracted from a hydrochloric acid solution into xylene with tributyl phosphate. After back-extraction with water, molybdenum is extracted as the α-benzoinoximate into chloroform, stripped into hydrochloric acid extracted as the thiocyanate into amyl alcohol, and determined spectrophotometrically. The molybdenum thiocyanate color produced is stable, sensitive, and reproducible. Results of analyses of several of the U.S. Geological Survey standard rocks are given.     

Spectrophotometric determination of molybdenum(VI)

Molybdenum(IV) gives a red colour with ammonium thiocyanate in 5-8M hydrochloric acid medium, the Sandell sensitivity index being 0.018 ppm Mo(VI)/cm(2). Molybdenum(VI) in 4-7M hydrochloric acid medium forms a red complex with ethyl xanthate and ammonium thiocyanate and this can be extracted into acetophenone. Beer's law is obeyed over the range of 1.2-13.8 ppm, and the Sandell indices at 370 and 470 nm are 0.0016 and 0.0068 ppm/cm(2) respectively. The colour is stable for 40 hr. Most cations do not interfere.