Application of atomic spectroscopic techniques to the analysis of oilwell brines and solids
The material presented in this thesis falls into two main sections: 1. The determination of barium, strontium and calcium in oil-well waters (i) Determination of barium It is revealed that the addition of magnesium (5 g l-1) to samples for the determination of barium by d.c. plasma atomic emission spectrometry enhances the sensitivity of the analysis and dramatically reduces interference from calcium and strontium at both atomic and ionic emission wavelengths. (ii) Determination of strontium The determination of strontium in waters, was also subject to the interference of the concomitant elements like calcium, barium and magnesium. However, the addition of 3 g l-1 sodium with or without 5 g l-1 of magnesium eliminated all the interferences in the d.c. plasma and in the dinitrogen oxide-acetylene flame. (iii) Determination of calcium The determination of calcium in oil-well waters encountered some interference arising from the presence of sulfate. However, the effects of phosphate and sodium were also investigated in both air-acetylene and dinitrogen oxide-acetylene flames and in the direct current plasma. It was shown that the interference was reduced in the cool flame when 2 g l-1 of lanthanum was added. The absorbance of calcium was depressed by the presence of 2 g l-1 of sodium. The interferences from both sulfate and phosphate were eliminated when the hot flame or the d.c. plasma were used. 2. Slurry nebulization for soil, sediment and fertilizer samples A slurry atomisation direct current plasma (DCP) emission and flame atomic absorption and emission (FAAS and FAES) for the determination of alkaline earth elements and also of other minor and major elements in soils, marine sediments and fertilizer is reported. The results obtained by slurry nebulization, with lithium added as ionisation buffer, were compared with results obtained following fusion with LiBO2 at 950o for 10 minutes and dissolution of the residues in 4&'37 HNO3.