The analysis of very small samples by atomic emission from a hollow cathode discharge source is investigated. Subpicogram detection limits of 0.88, 0.72, 0.38, and 0.70 pg are reported for Li, Na, K, and Ca, respectively, by viewing the excitation from a very small hollow with a custom-built multichannel spectrometer. These detection limits are comparable to those from electrothermal atomic absorption, with the additional advantage of the ability to analyze nonmetals. The technique has adequate sensitivity for the analysis of microsamples of physiological fluids for Na, K, and Ca; similar methods may be successful for Mg, P, and Cl, which are of significant physiological interest. Literature of applications of the hollow cathode as an emission source is reviewed. Instrumentation, operation, and sample preparation procedures are described. Temporal profiles of the emission from very small samples deposited in the hollow and working curves are given.
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