A comparison between quadrupole, double focusing and multicollector ICP-MSinstruments. Part I. Evaluation of total combined uncertainty for lead isotope ratio measurements
Jr. Encinar et al., A comparison between quadrupole, double focusing and multicollector ICP-MSinstruments. Part I. Evaluation of total combined uncertainty for lead isotope ratio measurements, J ANAL ATOM, 16(4), 2001, pp. 315-321
A quadrupole-based instrument (HP-4500), a double focusing single collector
instrument (Element) and a single focusing multicollector (IsoProbe) were
all evaluated for the precise and accurate measurement of lead isotope rati
os using Tl as internal isotope ratio standard. The isotope ratio accuracy
was evaluated using NIST 981 Common Lead Isotope standard reference materia
l and an enriched Pb-204 spike. Mass bias correction was performed using an
exponential model in all the three instruments and equations for the evalu
ation of the total combined uncertainty arising from the correction for the
dead time and mass bias were developed. It was observed that, in the corre
ction for mass bias, the uncertainty in the natural Tl ratio was the main s
ource of uncertainty for the multicollector instrument while, for the quadr
upole and double focusing single collector instruments, the measured isotop
e ratio was the main source of uncertainty.