Spectrochemical determination of impurities in telluric acid

An emission spectrographic method is described for determination of 20 elements present as impurities in telluric acid. Samples are excited in a 12-A. d.c. arc with the use of NaCl-KCl as a spectrographic buffer and germanium as internal standard. The limit of determination lies between 10(-5) and 10(-2)%. The precision of the method calculated as relative standard deviation is 10-25%.     

Matrix effect in the atomic emission determination of impurities in arsenic

Changes in the intensities of analytical lines due to impurities in the arsenic—graphite powder binary system were studied. It was found that these changes exhibited a complex nonlinear character. Factors responsible for the observed effect were examined.     

Spectrochemical determination of germanium in tar ashes

A technique for the emission spectrographic determination of germanium in tar ashes is described. Internal standardization was employed, Ge 2651.178 Å and Fe 2645.427 Å being the analysis pair. The effects of varying matrix were diminished by making up the Fe contents of the samples to a convenient limit, and by the addition of calcium carbonate. The technique, applicable to materials of reasonably different matrices, gives a precision of the order of 8–9%, expressed as standard deviation.     

Spectrochemical determination of tungsten and boron in mineral matrix

The spectrochemical behavior of nonvolatile tungsten and boron was tested by adding different buffers and using 12 A ac arc excitation. The oxidization and sulfidization processes were found to be most effective for facilitating the volatilization. The optimal admixture was the copper oxide buffer for both the detection limit and the precision of the method. The reference values of the background or a palladium line blackening were used.     

Spectrochemical determination of rare- earth metals in uranium and its salts

An emission spectrographic procedure is described for the determination of 0.05-4 ppm of rare-earth metals in uranium metal and its salts. Uranium is extracted from the sample with tributyl phosphate, and the impurities are separated by precipitation as hydroxides and oxalates, with yttrium as a carrier. After conversion into the oxides, the rare-earth metals are mixed with graphite and excited in a d.c. arc.     

Spectrochemical determination of trace bismuth and lead in iron-base and high-temperature superalloys

A method is presented for determination of lead and bismuth in steels and superalloys, based on co-precipitation with manganese dioxide followed by optical-emission or atomic-absorption measurements. The limit of determination is about 0.0001% and the relative standard deviation is 4% at the 0.002% level.     

Spectrographic determination of trace impurities in sulphur

Summary An emission spectrographic method for the estimation of traces of some common impurites viz., Al, Ba, Bi, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, Ti and V in high-purity sulphur is described. The impurities separated from 1-g sample, after removing sulphur as SO₂ by heating it in air at about 300° C, were dissolved in a small amount of 6M hydrochloric acid and loaded on 10 mg of carrier mixture containing 90% graphite and 10% sodium chloride in the 1/4 electrode crater. The spectra were exited in a D. C. arc carrying 13 A current for 45 seconds. Cobalt was used as an internal standard and sodium chloride as a carrier. The lowest detection limits lie in the range 0.005 to 0.05 ppm for the different elements. The precision of the method ranges from 6–19% for the elements analysed.

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Zusammenfassung Eine emissionsspektrographische Methode zur Bestimmung üblicher Spuren-Verunreinigungen in hochgereinigtem Schwefel, wie Al, Ba, Bi, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, Ti und V, wurde beschrieben. Die aus 1 g Schwefel, nach dessen Entfernung als SO₂ durch Erhitzen an der Luft bei etwa 300° C, abgetrennten Verunreinigungen werden in wenig 6-m Salzsäure gelöst und mit 10 mg Trägergemisch, bestehend aus 90% Graphitpulver mit 10% Natriumchlorid, in die Vertiefung einer 1/4-Elektrode eingebracht. Das Spektrum wird im Wechselstrombogen von 13 A für 45 sec angeregt. Kobalt dient als interner Standard mit Kochsalz als Träger. Die unterste Nachweisgrenze liegt bei 0,005–0,05 ppm für die verschiedenen angegebenen Elemente. Die Genauigkeit beträgt 6–19%.

     

Gas chromatographic determination of impurities in nitromethane

Summary Impurities in commercially available nitromethane have been determined by gas-liquid chromatography using six different column packings. Besides nitromethane, 1-nitropropane, 2-nitropropane, acetonitrile, methanol, small amounts of ethanol and acetaldehyde have been detected. The presence of formaldehyde, ethyl acetate and acetone is probable. Mixtures containing comparable amounts of the four nitroalkanes could be separated on all columns, but plots of logarithms of the retention times vs. carbon number or boiling points of the nitroalkanes or column temperatures were linear only in case of columns packed with Porapak R and Q.     

Polarographic determination of impurities in high-purity phosphorus

Square-wave and radio-frequency polarographic techniques in phosphoric acid-potassium chloride media are applied to the simultaneous determination of copper, lead and cadmium in highpurity red phosphorus down to a level of 0.1 ppm. In addition ca. 0.01 ppm of cadmium is determined by R.F. polarography in potassium sulphate base electrolyte after cation-exchange separation.     

Spectrochemical determination of trace uranium by an argon-stabilized U-shaped DC arc

An argon-stabilized U-shaped DC arc with the system for aerosol introduction was used for uranium determination. High uranium toxicity suggests the necessity of developing as sensitive methods as possible for U detection in various natural samples and complex matrices. By optimizing the operation conditions of U-shaped arc plasma and by applying an appropriate computer program that performs temporal integration of recorded signals, the measurement precision as well as the concentration sensitivity were improved, and the detection limit was lowered. Uranium detection limit, obtained by the application of U-shaped arc plasma during different integration times, decreases by increasing integration time. By increasing this time from 1 to 30 s, the detection limit was 37 times lower and the lowest detection limit is 0.07 μg/mL. The detection limit achieved by this method is comparable with the detection limits obtained by such methods as inductively coupled plasma-atomic emission spectroscopy (ICP-AES), direct coupled plasma-atomic emission spectroscopy (DCP-AES), and microwave induced plasma-atomic emission spectroscopy (MIP-AES). The text was submitted by the authors in English.     

Amplification-spectrophotometric determination of arsenic

Arsenic in submicroamounts is determined by use of the iron(II) ferrozine complex and measurement of the absorbance of the complex at 562 nm. The arsenic in the sample is converted into 12-arsenomolybdic acid and extracted into a mixture of butyl acetate and ethanol. The extracted complex is decomposed with sodium hydroxide and the Mo(VI) liberated is reduced to Mo(III) with a Jones reductor, then oxidized back to Mo(VI) with Fe(III). The resulting Fe(II) is complexed with ferrozine, and the absorbance measured. The high sensitivity of the method is due to the chemical amplification (factor of 36) that is involved in the procedure. The apparent molar absorptivity for this method is 9.44×10⁵ 1· mole^–1·cm^–1, compared to the theoretical value of 10.04×10⁵. The overall efficiency of the conversion is 94%.     

Neutron activation determination of impurities in germanium

A neutron activation (NA) method for the determination of 24 microimpurities in germanium has been developed. The method is based on the separation of the matrix and isotopes genetically connected by extraction chromatography.     

Polarographic determination of copper, arsenic and arsenic in copper arsenite

A method is proposed in which Cu^II, As^III and As^v can be determined in copper arsenite without prior separation. It is based on the fact that Cu^II and As^III yield prominent, distinguishable, widely-separated cathodic polarographic waves in a 0.1M LiCl-0.01M EDTA—0.001M LiOH solution using a dropping mercury electrode, whereas As^v does not give a wave in this medium. The As^v is determined by difference after reduction with sulphurous acid.     

Gas-chromatographic determination of carbon-containing impurities in high-purity sulfur

A gas-chromatographic procedure was developed for the determination of carbon-containing impurities in sulfur with a detection limit of 6 x 10^-6%. Carbon-containing substances and elemental carbon can be effectively separated from sulfur samples as CO₂ and COS.     

Direct spectrographic determination of impurities in uranium tetrafluoride

A direct spectrographic method for tlic determination of some impurities in UF₄ is described. The sample in the graphite electrode was covered with a layer of alumina before the arc was struck; alumina prevents the volatilization of UF₄ and thus avoids high spectral and background interferences. To stabilize the discharge, a controlled atmosphere of argon and oxygen was used. The impurity elements were divided into 3 categories according to their volatility: high (B, Si), medium (Co, Mn, V, Mo, Ti, etc.), and low (Ni, Pb, alkaline earths, etc.). Impurities of high and medium volatility could be determined with germanium or aluminum as internal standard. The sensitivities found for this method generally agreed with those of the carrier distillation method. The coefficients of variation varied from 8 to 25% at the 25 p.p.m. level.