Precise Measurement of Isotope Ratios with a Double-Focusing Magnetic Sector ICP Mass Spectrometer

The potential of a commercially available double focusing magnetic sector ICP-mass spectrometer (Element, Finnigan MAT, D) for precise isotope ratio measurement at the low resolution setting (R = 300) was evaluated. Optimization of scanning conditions permitted a relative standard deviation for a set of 10 consecutive 2 min measurements of about 0.1% RSD at signal intensities of ca. 200,000 cps (peak height). This compares favourably with the best values ever reported for quadrupole ICP-MS and barely exceeds the theoretical value (counting statistics). Increasing the signal intensity to values 500,000 cps resulted in a further reduction of the RSDs obtained to values of typically 0.04%. These figures are remarkably better than those reported for commercially available quadrupole ICP-MS systems. This improvement significantly reduces the difference between isotope ratio precision of ICP-MS on one hand and those of thermal ionization mass spectrometry and plasma source multiple collector mass spectrometry on the other.

VANHAECKE Frank;  MOENS Luc;  DAMS Richard;  TAYLOR P.D.P.; 

1996-07-29

JRC12733