Effective elimination of isobaric ions interference and precise thermal ionization mass spectrometer analysis for boron isotope

摘要

An ionization depressor, 1% H_3PO_4 was used to eliminate the isobaric interference that has been of a great concern during the procedure of boron isotopic ratio analysis by thermal ionization mass spectrometer (TIMS). Our experiments have shown that it appears to be an effective method to completely restrain the formation of isobaric ions of CNO~- and Cs_2CNO~+ in the ionization source of mass spectrometer. We have also discussed the optimum proportion of depressor to nitrite for precise analysis of boron isotopes in natural samples based on a conditional experiment. In this case, the pretreatment of boron extraction from natural samples is greatly simplified since it is not necessary to remove nitrite and organic matter completely. In virtue of the method, we determined boron isotope in different types of natural samples, and our results are consistent with previous reports.