A new
method was developed for rapid and precisesi
multaneous deter
mination of Mg/Ca, Sr/Ca, Mn/Ca,Cd/Ca, Ba/Ca and U/Ca ratios in fora
miniferal shellsusing sector field inductively coupled plas
ma
mass spectro
metry (ICPMS). Ele
ment/calciu
m ratios were deter
mined directly fro
m intensity ratios using external,
matrix-
matched standard to correct for instru
mental
massdiscri
mination. Because of large differences in the abundance of che
mical constituents of the fora
miniferal shell,
major ele
mental ratios were deter
mined in analog
mode(using
24Mg,
43Ca,
44Ca,
55Mn, and
88Sr) whereas traceele
mental ratios were deter
mined in pulse-counting
mode(using
111Cd,
138Ba,
238U, and the low-abundance
46Caisotope). Matrix-induced variations in
mass discri
mination over a calciu
m concentration range of 2.0-24.5
mMwere observed only for Mg/Ca and Cd/Ca ratios. However,these effects are negligible if the sa
mples and standardcalciu
m concentration are within a factor of 2-3. Multiratio
method reproducibility was better than previouslyreported for other ICPMS
methods yielding precision (1
![](/i<font color=)
mages/gifchars/sig
ma.gif" BORDER=0 >)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% forfora
minifera sa
mples as s
mall as 25
![](/i<font color=)
mages/entities/
mgr.gif">g. Using thisapproach for a single-ratio analysis, Sr/Ca ratios weredeter
mined with precision of 0.06% (1
![](/i<font color=)
mages/gifchars/sig
ma.gif" BORDER=0 >) on carbonatesa
mples as s
mall as a single fora
minifera shell (<10
![](/i<font color=)
mages/entities/
mgr.gif">g).The new
method is
more sensitive,
more precise, andsi
mpler to use than previously available ICPMS techniques. It provides an efficient tool for si
multaneousdeter
mination of several ele
mental ratios of paleoceanographic interest in a single fora
miniferal sa
mple, therebyreducing overall sa
mple size require
ment and analysisti
me.