Izotop-nisbati massa spektrometriyasi ( irms )

Isotope-ratio mass spectrometer used to measure 
stable isotope
 ratios, with gas bench in foreground

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It is critical that the sample be processed
before entering the mass spectrometer
so that only a single chemical species
enters at a given time. Generally, samples
are combusted or pyrolyzed and the
desired gas species (usually hydrogen
(H
2
), nitrogen (N
2
), carbon dioxide (CO
2
),
or sulfur dioxide (SO
2
)) is purified by
means of traps, filters, catalysts and/or
chromatography.
The two most common types of IRMS
instruments are continuous flow
[7]
and
dual inlet. In dual inlet IRMS, purified gas
obtained from a sample is alternated
rapidly with a standard gas (of known
isotopic composition) by means of a

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system of valves, so that a number of
comparison measurements are made of
both gases. In continuous flow IRMS,
sample preparation occurs immediately
before introduction to the IRMS, and the
purified gas produced from the sample is
measured just once. The standard gas
may be measured before and after the
sample or after a series of sample
measurements. While continuous-flow
IRMS instruments can achieve higher
sample throughput and are more
convenient to use than dual inlet
instruments, the yielded data is of
approximately 10-fold lower precision.

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A static gas mass spectrometer is one in
which a gaseous sample for analysis is
fed into the source of the instrument and
then left in the source without further
supply or pumping throughout the
analysis. This method can be used for
'stable isotope' analysis of light gases
(as above), but it is particularly used in
the isotopic analysis of noble gases (rare
or inert gases) for radiometric dating or
isotope geochemistry. Important
examples are argon–argon dating and
helium isotope analysis.
Statik gaz massa
spektrometriyasi

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Several of the isotope systems involved
in radiometric dating depend on IRMS
using thermal ionization of a solid
sample loaded into the source of the
mass spectrometer (hence thermal
ionization mass spectrometry, TIMS).
These methods include rubidium–
strontium dating, uranium–lead dating,
lead–lead dating and samarium–
neodymium dating.
When these isotope ratios are measured
by TIMS, mass-dependent fractionation
occurs as species are emitted by the hot
Termal ionlanish massa
spektrometriyasi

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filament. Fractionation occurs due to the
excitation of the sample and therefore
must be corrected for accurate
measurement of the isotope ratio.
[8]
There are several advantages of the
TIMS method. It has a simple design, is
less expensive than other mass
spectrometers, and produces stable ion
emissions. It requires a stable power
supply, and is suitable for species with a
low ionization potential, such as
Strontium (Sr), and Lead (Pb).
The disadvantages of this method stem
from the maximum temperature
achieved in thermal ionization. The hot

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filament reaches a temperature of less
than 2500 degrees Celsius, leading to the
inability to create atomic ions of species
with a high ionization potential, such as
Osmium (Os), and Tungsten (Hf-W).
Although the TIMS method can create
molecular ions instead in this case,
species with high ionization potential can
be analyzed more effectively with MC-
ICP-MS.
Ikkilamchi ionli massa
spektrometriyasi
[ ]

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An alternative approach used to measure
the relative abundance of radiogenic
isotopes when working with a solid
surface is secondary-ion mass
spectrometry (SIMS). This type of ion-
microprobe analysis normally works by
focusing a primary (oxygen) ion beam on
a sample in order to generate a series of
secondary positive ions that can be
focused and measured based on their
mass/charge ratios.
SIMS is a common method used in U-Pb
analysis, as the primary ion beam is used
to bombard the surface of a single zircon