Determination of cesium, rubidium and lithium by stabilized DC arc plasma emission spectrometry
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Optimization of the conditions for the analytical application of a vertical argon stabilized DC are plasma, seeded by an easily ionizable element, potassium, is described. Such a plasma is used as an excitation source for the direct determination of Ca, Rb and Li. A high potassium chloride content in the solutions (of the order of 1%), significantly lowers the excitation temperature, which causes a suppression of the high energy processes (and of the corresponding spectral lines). The signal to background ratio of the moderate to low excitation potential lines increased by 10-100. Calibration was carried out under optimal conditions, and detection limits in the range 23.5 mu g/dm(3) to 0.055 mu g/dm(3) were reached, with linearity across 4-6 orders of magnitude. The method was successfully applied for the direct determination of Li, Rb and Cs in mineral water samples that, for comparison, were also analyzed by flame emission spectrometry. Good agreement between the two methods was achi...eved. The accuracy of the method was verified by the international reference standard SRM 1643d.