MULTIELEMENT ANALYSIS OF MICROSAMPLES OF RENAL FLUIDS

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The long range goals of this research in atomic spectroscopy are to develop and improve quantitative methods for the analysis of both metal and nonmetal elements in biological samples requiring either microanalysis or trace analysis. The ability to analyze microsamples of biological fluids for several elements is necessary in modern renal physiology. Techniques which are dependent upon microanalytical and which generate microsamples in the range of pL to nL include: single nephron micropuncture, isolated tubule microperfusion, and microinjection. Each of the analytical methods presently available has drawbacks for some applications. Perhaps the most serious deficiency is that, sample, thus separate determinations by different methods are usually required. The specific goals for this proposed project are to: Develop instrumentation and procedures which will allow objective evaluation of the pulsed hollow cathode emission source for multielement analysis of both micro- and macro samples. The primary objective is a useful method for the microanalysis of renal fluids needed in renal research. A secondary objective is to determine the likely utility of this technique as a general analytical trace method; determine if, indeed, a variety of both metals and nonmetals can be analyzed simultaneously in muL- sized samples. Subpicogram detection limits and good precision have been demonstrated in this laboratory for most of the six elements of prime interest to renal physiology using the hollow cathode discharge. In addition to multielement capability, the hollow cathode source is uniquely capable of analyzing nonmetals as well as metals in both micro- and macrosamples. We can routinely produce linear working curves with subpicogram detection limits and we have extended the working range of analyte mass to 120 pg. Next, the hollow cathode method must be adapted to renal samples in which the minor elements (K, Ca, Mg, and P) are in a matrix of 30 to 150 times as many moles of Na and Cl. In addition, the effect of the small amount of protein and urea present in real renal samples must be evaluated. Pulsed operation of the hollow cathode discharge will be extensively investigated using pulse widths as small as 0.1 mus, repetition rates as high as 5 KHz, and currents up to 1 A. Aluminum and graphite cathodes will be evaluated and compared to that of copper for the analysis of renal fluids. Scanning electron microscopy will be used to study microscopic effects important to the precision and intensity of the emission signal from the hollow cathode, these effects include: 1) Erosion of electrode surfaces by sputtering and subsequent effects of the rough surface on sample excitation. 2) The form or shape of the sample deposit as correlated with sample deposition procedure and the quality of the emission signal.