10/27/2009
GLOSSARY OF IMPORTANT TERMS
ICP-MS: Inductively Coupled Plasma Mass
Spectrometry
´ Base Peak
´ Collision
C lli i Chamber
Ch b
´ CAD: Collisionally Activated Decomposition
´
http://mgg.rsmas.miami.edu/groups/sil/webdoc1_files/image004.jpg
USES:
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MASS SPECTROMETRY
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-------------------Geochemistry
«
Identify structure of biomolecules such as lipids, carbohydrates, etc.
Detect traces of banned substances in athletes
Determine composition of rocks to determine their age and origin
Identify isotopes of various elements
Perform forensic analysis
WHAT IS A MASS SPECTROMETER?
WHAT DOES THAT MEAN?
An instrument that ionizes sample molecules
and separates ions according to their mass-tocharge (m/z) ratio.
´ Dalton (Da) = 1/12 the mass of single atom of
the isotope 12C.
´ Charge of most ions = 1; explains why m/z
value is equal to the molecular mass.
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Atoms must first be IONIZED.
´ Ions are accelerated to have the same KINETIC
ENERGY.
´ Ions
I
are deflected
d fl t d b
by a MAGNETIC FIELD.
FIELD
´ Ions are then detected ELECTRICALLY.
http://www.chemguide.co.uk/analysis/masspec/howitworks.html
IONISATION
Producing ions in a vacuum is important because the ions need to run
through the machine without hitting air molecules.
DEFLECTION
The amount of deflection depends on 1)the mass of the ion: lighter ions are
deflected more than heavier ones, and 2) the charge on the ion: higher
positively charged ions are deflected more than ions with only one positive
charge.
The positively charged ions are
accelerated into 3 charged slits before
beginning deflection.
http://www.chemguide.co.uk/analysis/masspec/howitworks.html
http://www.chemguide.co.uk/analysis/masspec/howitworks.html
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DETECTION
WHAT IS RECORDED?
Ions that pass through the deflection chamber hit a metal box. This
creates a space between the ion and wire along which electrons flow.
The current of electrons along the wire can be recorded. The mass can
be recorded based on the amount if ions arriving on the metal box and
the current of electrons.
Stick Diagram records the relative
current produced by ions of varying
mass/charge ratio.
http://www.chemguide.co.uk/analysis/masspec/howitwor
ks.html
http://www.chemguide.co.uk/analysis/masspec/howitworks.html
HERE’S HOW IT WORKS…
PROBLEMS WITH THE MASS SPEC
Time: MS can take up to 24 hours just to run a
single tray of samples.
´ The MS can only run 38 samples with 6
standards.
standards
´ Light ions may cling together and be sampled
as a heavier ion.
´ Sample size must be accurate or results may
be skewed.
´ Not reliable machines.
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REFERENCES
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“What is Mass Spectrometry.” American Society for Mass Spectrometry. 1
Dec. 2001. Web. 21 Sept. 2009
Clark, J., 2009. “The Mass Spectrometer.” Chem Guide. Web. 21 Sept 2009.
www.chemguide.co.uk.
Gross, J. Mass Spectrometry. Springer 2004.
Mallet A
Mallet,
A., 2005
2005. “Mass Spectrometry Glossary of Terms
Terms.”” Base Peak.
Peak 28
Sept. 2005. Web 24 Sept. 2009.
http://www.spectroscopynow.com/coi/cda/detail.cda?id=10122&type=Edu
cationalFeature&chId=4&page=1.
Rollinson, H. Using Geochemical Data. London: Longman Group, 1993. pp
14-15.
The Rosenstiel School of Marine and Atmospheric Sciences (RSMAS)
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