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- × 5-mm stainless steel cathode. A scanning electron microscope was used to study the surface structure resulting from the conditioning. The resulting hollow bottom was bulb-shaped and the surface was mirror-like, very smooth, and shiny. The emission intensities from smooth cathodes were greater that those 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 were made on different days with different cathodes that had been conditioned in the same manner for 4 h by sputtering. The three working curves virtually coincided when plotted in the same figure, demonstrating the precision and reproducibility from day to day of the hollow cathode discharge method as developed in this laboratory. The 3-σ detection limits calculated from slopes of working curves are 0.32 pg, 0.35 pg, and 3.2 pg for Na, Li, and K, respectively.