F.J. Langmyhr

The analysis of inorganic siliceous materials by atomic absorption spectrophotometry and the hydrofluoric acid decomposition technique : Part I. the analysis of silicate rocks

Abstract The analysis of various inorganic siliceous materials of geological and industrial interest is discussed. The methods proposed are based on decomposition of a single sample by hydrofluoric acid and determination by atomic absorption spectrophotometry of up to 10 constituents. General procedures are described, and details are given for the determination of silicon, aluminium, total iron, magnesium, calcium, sodium, potassium, titanium and manganese in silicate rocks. Analytical data are given for the analysis of reference rocks G-2 and W-1.

Direct electrothermal atomic absorption spectrometric determination of selenium in serum

Abstract The effect of copper, iron, nickel and silver ions on the thermal stability of inorganic and metabolized forms of selenium in serum was studied with radioactive 75Se. Copper and iron had no stabilizing effect but in the presence of nickel or silver the temperature could be raised to 1050°C or 1250°C, respectively, without loss of selenium. On this basis an electrothermal atomic absorption spectrometric method was developed for the direct determination of selenium in human serum; selenium is stabilized with nickel during ashing. In 12 samples of sera from unexposed individuals, the concentrations ranged from 92 pob to 140 ppb. The relative standard deviation of the method is 4%, and the detection limit is 5 ppb.

Decomposability in hydrofluoric acid of the main and some minor and trace minerals of silicate rocks

Abstract The decomposability in hydrofluoric acid of a selection of 28 main and some minor and trace minerals of silicate rocks was investigated. 21 minerals were decomposed successfully by heating on the water bath ; the remainder - with the exception of topaz-were found to be decomposable at the higher temperatures of a teflon-lined bomb. The results indicate that hydrofluoric acid alone is more effective as decomposing agent than a mixture containing another mineral acid.

A modified and a new straight-line method for determining the composition of weak complexes of the form AmBn

Abstract A modified Asmus method and a new method are described for determining the composition and stability of weak complexes of the form A m B n . The modified method is applicable to polynuclear complexes and is not based on the approximation necessary originally. The second method is based on variation of the concentration of the reactant being maintained in excess. The method gives a straight line for the correct quotient of n/m and the stability constant can easily be calculated from data extracted from the diagram. The main advantage is that, in combination with the original straight-line method, this method permits the determination of both coefficients m and n in the presence of an excess of one of the reactants

Atomic absorption spectrometric determination of cadmium, lead, silver, thallium and zinc in silicate rocks by direct atomization from the solid state

Abstract Atomic absorption spectrometric methods are described for the determination of cadmium, lead, silver, thallium and zinc in some international and other silicate rocks. The metals are atomized directly from the solid samples in a graphite furnace. The data are compared with results obtained by atomizing solutions in the flame, in the graphite furnace, and with earlier data.

The use of the method of continuous variation for the classification of complexes with mole ratio 1:1

Abstract It is shown theoretically and experimentally that curves of continuous variation may be used to classify complexes of the form AmBn for which m n = 1, into two different groups: one group comprises complexes for which m = n = 1, and another group contains those for which m = n > 1. The system iron(III)-chrome azurol S was used to demonstrate the applicability of the method.

Thermal stabilization of inorganic and organically- bound tellurium for electrothermal atomic absorption spectrometry

Abstract The thermal stabilization of inorganic tellurium(IV) and organically-bound tellurium for electrothermal atomic absorption spectrometric determination of the element was studied with the use of the isotope tellurium-127m. Of the 19 metals and potassium iodide tested, 15 metals had a stabilizing effect on inorganic tellurium; among the 9 metals tested with organically-bound tellurium, only 3 exhibited an effect. The most effective metals for stabilizing inorganic tellurium were cadmium, copper, palladium, platinum and zinc, while the best agents for stabilization of organically-bound tellurium were silver, palladium and platinum; in the presence of palladium and platinum, tellurium in both forms could be heated in the graphite tube to 1050°C without losses. Attempts were made to determine tellurium in human whole blood and garlic, but the concentrations were found to be below the detection limits of 3 ng ml-1 and 140 ng g-1, respectively.

Atomic-absorption spectrometric determination of cadmium, lead and zinc in salts or salt solutions by hanging mercury drop electrodeposition and atomization in a graphite furnace

Abstract Atomic absorption spectrometric methods are described for the determination of trace amounts of cadmium, lead and zinc in salts or salt solutions. The metals are separated from the salt matrix by electrolysis on a hanging mercury drop electrode, the mercury is transferred to a graphite boat and removed by evaporation, and the metals are determined by atomization. The feasibility of the technique was tested by analysis of sea water and of reagent-grade potassium chloride. For comparison the three metals were also determined in the sea water by stripping voltammetry, good agreement being found.

The applicability of the “straight-line method” of asmus in the determination of the composition of polynuclear complexes

Abstract The straight-line method of Asmus was originally developed for the determination of n in mononuclear complexes of the general form ABn (n≧ 1). In the present investigation it is demonstrated that the method also can be used for determining the value of n in polynuclear complexes of the form A[mBn (m > 1). The method as suggested by Asmus, is, however, not capable of distinguishing between mono- and polynuclear species. It is further shown, that the straight-line method can be applied for the determination of the value of m.

The application of electrodeposition techniques to flameless atomic absorption spectrometry : Part IV. Separation and preconcentration on graphite

Abstract A new flameless atomic absorption technique for the determination of trace metals in a salt matrix is described. The elements to be determined are electrolyzed on to a graphite electrode, the exposed part of which is ground, and a portion of the graphite powder is finally analyzed directly by flameless atomic absorption in a graphite furnace. Many elements can be determined from a single electrochemical deposition. The graphite powder may also be stored for later control analysis. The effects of various experimental parameters are described. The method is applied to the determination of trace metals in commercial salts.