RESUMO
The element content of low and high sulfur containing diesel fuels was measured by different analytical methods: energy-dispersive X-ray fluorescent (EDXRF) and inductively coupled plasma atomic emission (ICP-OES) spectroscopy methods. Then results were compared. High sulfur containing diesel fuels were from heavy diesel engines and diesel fuel-like liquids obtained by thermal degradation of waste polymers. In case of X-ray analysis also the effect of the used thin foils with different chemical compositions (polypropylene, polycarbonate, polyester) on the accuracy was investigated. According to data considerable differences and deterioration of accuracy was observed in the respect of foils in case of both low and high sulfur containing hydrocarbons. Results indicated appropriate correlation between experimental results measured by both two methods, but differences could be observed in the correlation, which could be explained with different ratio of C/H of samples.
RESUMO
High purity fluorapatite (FAP) was prepared by solid state reaction, in flowing argon gas, at 1370 degrees C for 60 min. For chemical characterization of Ca(10)(PO(4))(6)F(2), the accuracy and reproducibility of different analytical methods were assessed. Methods with a good accuracy for the determination of Ca, P and F content were: titrations with EDTA for Ca determination (accuracy: -0.8%), spectrophotometric method for P determination (accuracy: +0.6%) and measurements with fluoride-selective electrode (accuracy +5.4%) for F determination.
RESUMO
Pressurized sample preparation devices (High Pressure Asher, Pressurized Microwave Digestion system, compared with a PTFE decomposition vessel) were used to dissolve certified metal alloy samples (steel, copper) for ICP analysis. Based on the results of the analysis it was established that both up-to-date devices can be advantageously applied to quickly and quantitatively dissolve metal alloy samples. To dissolve the samples, two different kinds of acid mixtures (A: nitric and hydrochloric acid; B: nitric and hydrochloric and sulphuric and phosphoric acid) were used. The sample preparation is simpler and less time-consuming than the earlier commonly used methods, sample loss and degree of contamination are also reduced. Steel samples containing tungsten, titanium and niobium (less than 0.5%) can only be analyzed using a mixture of the four acids. By dissolving steel samples in the nitric and hydrochloric acid mixture, the concentration of their most common elements (Cr, Ni, Mn, V, Cu) as well as their S and P content can be determined. Copper alloy samples can be dissolved quickly by the pressurized microwave decomposition device using hydrochloric acid and diluted (1:1) nitric acid.
RESUMO
Outer-sphere complex formation reactions have been used to increase the selectivity of ion-exchange separation of maleate and fumarate ions. The stability constants of the maleate and fumarate complexes of tris(ethylenediamine)cobalt(III) and hexa-amminecobalt(III) have been determined at different ionic strengths from the elution volumes and the parameters of the ion-exchanger bed, and the values at I = 0 obtained by extrapolation. They are: log K [Co(en)(3+)(3) + Ma(2-)] = 3.33; log K [Co(NH(3))(3+)(6) + Ma(2-)] = 3.77; log K [Co(en)(3+)(3) + Fu(2-)] = 1.19; log K [Co(NH(3))(3+)(6) + Fu(2-)] = 1.99. The two anions can be separated quantitatively.
RESUMO
It has been found that outer-sphere complex formation reactions can be used to increase the selectivity of ion-exchange separations. A method has been developed for the quantitative separation of sulphate and oxalate. The stability constants of the sulphate and oxalate complexes of tris(ethylenediamine) cobalt(III) and hexa-amminecobalt(III) have been determined at different ionic strengths from the elution volumes and the parameters of the ion-exchanger bed, and the values at I = 0 have been obtained by extrapolation. They are log K[Co(en)(+3)(3) + SO(2-)(4)] = 3.38; log K[Co(NH(3))(3+)(6) + SO(2-)(4) = 3.60; log K[Co(en)(3+)(3) + C(2)O(2-)(4) = 3.23.
