ABSTRACT
The laser microprobe system introduced in 1962 1 was designed specifically for microsampling-microanalysis problems. A laser pulse is fired through a microscope focused on the sample surface to vaporize the microsection of the sample of interest. A high voltage spark, initiated by passage of the vapor plume through an electrode gap above the sample surface, is used to provide supplementary excitation of the constituents of the vapor plume. The system is capable of vaporizing sample from a surface with a spatial resolution of a few microns. Consequently, multielement emission spectrometric analyses are carried out on a sample which may be only a few micrograms in size. Even though high absolute sensitivities are realized by this method, relative concentration detectabilities are limited by the small amount of samples vaporized. The detection limits given in Table 6 were obtained by analysis of metal alloy standards using photographic recording of the spectra. A 3 μg sample was vaporized. Detection Limits with the Laser Microprobe
Element
Detection Limit * μg/g
Element
Detection Limit * μg/g
Ag
10.0
Mn
40.0
Al
200.0
Ni
210.0
B
40.0
Pb
250.0
Be
12.0
Sb
600.0
Bi
180.0
Si
270.0
Co
>700.0
Sn
450.0
Cr
60.0
Ti
280.0
Fe
240.0
V
830.0
Ga
80.0
Based on vaporization of 3 μg of sample by laser pulse.
From Snetsinger, K. G. and Keil, K., Am. Mineralogist, 52, 1842, 1967. With permission.