A new method was developed for rapid and precisesimultaneous determination of Mg/Ca, Sr/Ca, Mn/Ca,Cd/Ca, Ba/Ca and U/Ca ratios in
foraminiferal shellsusing sector field inductively coupled plasma mass spectrometry (ICPMS). Element/calcium ratios were determined directly from intensity ratios using external, matrix-matched standard to correct for instrumental massdiscrimination. Because of large differences in the abundance of chemical constituents of the
foraminiferal shell,major elemental ratios were determined in analog mode(using
24Mg,
43Ca,
44Ca,
55Mn, and
88Sr) whereas traceelemental ratios were determined in pulse-counting mode(using
111Cd,
138Ba,
238U, and the low-abundance
46Caisotope). Matrix-induced variations in mass discrimination over a calcium concentration range of 2.0-24.5 mMwere observed only for Mg/Ca and Cd/Ca ratios. However,these effects are negligible if the samples and standardcalcium concentration are within a factor of 2-3. Multiratio method reproducibility was better than previouslyreported for other ICPMS methods yielding precision (1
)of Sr/Ca = 0.45%; Mg/Ca = 0.45%, Mn/Ca = 0.8%, Cd/Ca = 1.7%, Ba/Ca = 0.7%, and U/Ca = 1.4% for
foraminifera samples as small as 25
g. Using thisapproach for a single-ratio analysis, Sr/Ca ratios weredetermined with precision of 0.06% (1
) on carbonatesamples as small as a single
foraminifera shell (<10
g).The new method is more sensitive, more precise, andsimpler to use than previously available ICPMS techniques. It provides an efficient tool for simultaneousdetermination of several elemental ratios of paleoceanographic interest in a single
foraminiferal sample, therebyreducing overall sample size requirement and analysistime.