Evaluation of the detection capability of a U-shaped d.c. arc for spectrometric analysis of solutions

A gas-stabilized arc with aerosol supply, originally designed for atomic absorption studies, has been used for emission spectrometric analysis of solutions. A characteristic of the arc is a fairly long horizontal part of the arc column which makes possible “end-on” observation of the spectral emission and selection of a well-defined region of the arc column for analysis. The most intense emission of continuum is at the arc column axis while the emission maxima of the nebulized elements are located at different distances from the axis, which mainly depend on the ionization potential of the corresponding element.The presence of alkali elements in the arc plasma enhance considerably the spectral emission of the elements with medium and low ionization potentials. The effect depends mainly on the first ionization potential of the element and its extent is approximately the same for atom and ion lines. In the case of potassium chloride the intensity increase approaches a plateau at a concentration of 2.5 mg ml^?1. The magnitude of the effect justifies the use of potassium chloride as a spectroscopic buffer.Detection limits obtained with this source on 60 spectral lines are compared with those found in inductively coupled plasmas and in an inverted V-arc echelle spectrometer system. Comparison reveals that inductively coupled plasmas yield consistently lower detection limits with the ion lines used, while with the atom lines it retains the advantage only for elements having a high ionization potential.