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Ellery --
Sobolev et al (Science, 2007) report 140 ppm Co for SCO USNM 111312/444
by Laser
ablation ICP-MS. They then use that value for SCO to calibrate Co in their
massive olivine study; they also measured 3 SCO's every 30-50 points as an
internal drift and accuracy check.
Their preferred EMP operating conditions were 20 kV & 300 nA (!) with 120 sec
counting times on the Max-Planck Jeol Jxa 8200.
Also, they determined a correction for the FeK second order shoulder
on Co K
by analyzing Fe bearing standards free of Co:
CoOc = CoOm - 0.0011~FeOm - 0.013.
Its not clear to me whether that correction would be ~ universal, or
need to be
determined for your particular machine.
They also report "the above measurement conditions routinely yield detection
limits of around 6-15 ppm based on 3 sigma criteria by Jeol standard software,
and errors of 15-30 ppm for trace elements and 0.01 mol% for Fo content (2
standard errors) established by counting statistics and reproducibility of
olivine standard (see Fig S1-S2)." Co & Mn precision, LA-ICP MS vs EMP, are
specifically compared in Fig S3.
Here's the link to the online supplement:
http://www.sciencemag.org/cgi/content/full/1138113/DC1
There is a massive amount of data there!
-- Malcolm
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If you don't feed the teachers, they will eat the children.
Anonymous teacher, told to Linda Albert, Cooperative Discipline, 1996.
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But none of that will transform education if we fail to cherish --
and challenge -- the human heart that is the source of good teaching.
Parker J Palmer, The Courage to Teach, 1998.
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Malcolm S Pringle, Dept. of Earth, Atmospheric, and Planetary Sciences
Massachusetts Inst of Technology, 77 Massachusetts Ave Bldg 54-1210
Cambridge, MA 02139-4307 USA Cell: 617-319-6584
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