The Design and Some Emission Characteristics of an Economical dc Arc Plasmajet Excitation Source for Solution Analysis

Abstract

The de-arc plasmajet has been applied to a large number of emission problems since its introduction in 1959 because it offers reduced matrix effects, stability, and moderate sensitivity. However, its use has been significantly limited due to operating costs associated with its high inert gas flow rates. A new excitation source, based on the principle of the plasma jet, has been developed that can operate at a much lower cost. The source operates from a conventional dc-arc power supply and uses commercially available electrodes. Total inert gas consumption is less than 2.5 liters/min. Stability of the source is better than 1% and reproducibility is approximately 4%. An excitation temperature of 5800 K was calculated from the relative intensities of several vanadium lines. The source can be operated continuously for several hours at a time. Design and some characteristics of the arc are presented. Detection limits are given for 12 elements. Six of the elements (Ca, Cr, Fe, Li, Ni, and Y) have detection limits below 10 ng/ml. Analytical response for the elements studied is linear over a wide concentration range. A calibration curve for Ca is presented which is linear over more than four orders of magnitude.