Potential for clinical use of the analytical laser microprobe for element measurement

Use of the laser microprobe for rapid emission spectroscopic analysis of elements in microscopic samples of biological material is described. The technique depends on vaporization of the microsample with a focused laser beam at a temperature that renders the vapor incandescent for spectrochemical analysis. Spectral line intensities are recorded photographically with densitometry of the negatives or photoelectrically. Current capability permits analysis of about 10(-8) to 10(-10) g of tissue, with detection limits of 10-12 to 10-15 g of element. Groups of elements can be simultaneously analyzed. Minimum sample preparation is required, and the analysis is done on the stage of a light microscope, usually on an air-dried sample on a plastic slide. We exemplify the technique in analysis of gold in cultured fibroblasts treated with gold salts and in human skin after treatment with gold salts for rheumatoid arthritis, in element changes in biopsies of transplanted human hearts, and in unique profiles of groups of elements in human cancer tissue.