Journal of Natural Disaster Science

ANALYTICAL TECHNIQUES FOR DETERMINING A MICRO QUANTITY OF CO2 IN VOLCANIC GLASS BY LASER PROBE MASS SPECTROMETRY

Genji SAITO
and
Minoru KUSAKABE
Institute for Study of the Earth's Interior, Okayama University Misasa, Tottori-keu 682-01, Japan

(Received 8 October and in revised form 13 January 1992)

Abstract

An analytical system has been developed for determining a micro quantity (0.1-1ng) of CO2 in volcanic glass. It consists of a Nd-YAG laser for the selective heating of small areas of volcanic glass and a gas chromatogragh-mass spectrometer for measuring the absolute amount of the CO2 extracted from the glass. The carbon dioxide concentrations of the glass samples were calculated from the mass of the melted glass and the measured amount of CO2. The glass sample ground to a thickness of less than 100 micor meter was pierced by a laser beam. The volume of the melted glass was controlled by changing the duration of the laser beam. The mass of the melted glass was calculated from its volume and density.

Analysis of homogenized basaltic glass with a bulk CO2 concentration of 326 ppm gave a CO2 concentration of 270±70 ppm when the extracted CO2 was more than 0.6 ng. Glass inclusions larger than 100 micro meter in diameter can be analyzed by the present method with an accuracy of ±70 ppm when the CO2 concentration is 300 ppm.

Key words

microanalysis, CO2 in volcanic glass, laser probe