RECENT DEVELOPMENTS IN THERMAL IONIZATION MASS-SPECTROMETRIC TECHNIQUES FOR ISOTOPE ANALYSIS - A REVIEW

Thermal ionization mass spectrometry in the positive or negative ioniz ation mode can be used for precise isotope ratio determinations of mos t elements, The preferably formed ions are M(+), M(-) and MO(x)(-) (x = 1-4), Recent interesting developments in this field, which are relev ant in geology, are the U/Th and Re/Os dating methods, redetermination s of the relative atomic masses of elements by more precise and more a ccurate isotope ratio measurements, the determination of isotope varia tions in geological and cosmic samples and the analysis of trace and u ltra-trace amounts of elements and elemental species in the environmen t, In order to measure accurately a low abundant isotope in addition t o a high abundant isotope (up to ratios of 10(9)), thermal ionization mass spectrometers with deceleration lens systems have been constructe d which fulfil the required abundance sensitivities, Chromium (III)I c hromium(VI) speciation below the mu g l(-1) level in different river w ater samples is reported as an example of the application of positive thermal ionization mass spectrometry in connection with the isotope di lution technique, Rhenium/osmium osmium determinations in iron meteori tes of group IIA and IAB are performed by using a corresponding separa tion procedure with an OsO4 distillation step and rhenium isolation by anion-exchange chromatography, The isochron for the IIA iron meteorit es results in an age of (4.54 +/- 0.08) x 10(9) years, These precise m easurements also indicate small deviations of the IAB silicate-rich ir on meteorite data from the IIA isochron, Precise boron isotope ratio m easurements by negative thermal ionization mass spectrometry are appli ed to determine anthropogenic influences in groundwater samples.