PILOT-STUDY OF THE ANALYTICAL PERFORMANCE OF THE PULSED HOLLOW-CATHODE DISCHARGE EMISSION SOURCE

Proper conditioning of the hollow cathode by sputtering is critical to the analytical performance of the hollow cathode. A pulsed discharge procedure was developed to condition the 1.5- x 5-mm stainless steel c athode. A scanning electron microscope was used to study the surface s tructure resulting from the conditioning. The resulting hollow bottom was bulb-shaped and the surface was mirror-like, very smooth, and shin y. The emission intensities from smooth cathodes were greater that tho se from the rough ones. The precision obtained here was 3-5% for Na, 5 -8% for Li, and 4-10% for K. Three working curves for each element wer e made on different days with different cathodes that had been conditi oned in the same manner for 4 h by sputtering, The three working curve s virtually coincided when plotted in the same figure, demonstrating t he precision and reproducibility from day to day of the hollow cathode discharge method as developed in this laboratory. The 3-sigma detecti on limits calculated from slopes of corking curves are 0.32 pg, 0.35 p g, and and 3.2 pg for Na, Li, and K, respectively.