ON SOME PREPARATION METHODS IN STABLE-ISOTOPE MASS-SPECTROMETRY AND THEIR GEOCHEMICAL APPLICATIONS

Preparation of samples and their introduction into the mass spectrometer are very important in stable-isotope mass spectrometry. The authors have found that using the Coleman method for hydrogen gas preparation from water an improved reproducibility can be achieved if the reaction tube containing the zinc and hydrogen gas is kept at > 350-degrees-C when the hydrogen is collected into the mass spectrometer for measurement. One of the critical conditions for the carbonate preparation is the quality of phosphoric acid. The reproducibility is better if before every preparation series the phosphoric acid is saturated adding phosphoric pentoxide to the acid at 150-degrees-C. As an application of stable-isotope mass spectrometry the origin of a certain limestone near Budapest (Hungary) has been determined after a long dispute among geologists.