A high-sensitivity laser microprobe mass analyzer

A laser microprobe mass analyzer has been developed. It is intended for application in biomedical and physiological research. A frequency-doubled ruby laser is focussed through an incident light microscope to a spot of minimally 0.5 μm in diameter on a thin section specimen of 0.1–1.5 μm thickness. The microplasma generated from the irradiated volume is analyzed in a time-of-flight mass spectrometer recording the complete spectrum for each shot. From lithium doped epoxy resin (5 ppm by weight), used as an organic standard, 1.4×10⁻¹⁹g or 1.4×10⁴ atoms of the⁶Li isotope have been detected. This sensitivity corresponds to that of ion microprobes but is at least an order of magnitude higher than obtained with electron probe X-ray microanalyzers.