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Finnigan™ GC-C/TC III
GC Interface for Compound
Specific Isotope Analysis
Analyze • Detect • Measure • Control™
Finnigan™ GC-C/TC III
GC Interface for Compound Specific Isotope Analysis
Finnigan™ GC-C/TC III
GC Interface for Compound Specific Isotope Analysis
The Finnigan GC-C/TC III interface from Thermo Electron Corporation is a state of the art GC interface
for the analysis of 13C/12C, 15N/14N, 18O/16O, and D/H. Organic compounds eluting from a GC column are
converted into simple gases when traversing a capillary micro-reactor. Accordingly all compound specific
isotope ratios can be analyzed in the IRMS.
Thermo’s Finnigan GC-C/TC III Interface provides the highest performance attainable for:
• Compound specific isotope analysis of δ13C, δ15N, δ18O, and δ2H
• All GC-volatile organic compounds
• Analysis into the picomole range
• Highest GC resolution due to true capillary design
• Quantitative high temperature combustion up to 1000 °C
• Quantitative high temperature pyrolysis up to 1500 °C
• Fractionation-free sample transfer
• Highest transfer rate into the IRMS
• Independent reference gas injection
The first Finnigan GC combustion system for
13
C/12C (δ13C) determination was introduced
in 1988, opening the new field of compound
specific isotope analysis (CSIA). This
technique combines the exquisite chemical
resolution of capillary GC with the high
precision of isotope ratio mass spectrometry
(IRMS).
Thermo Electron added the capability
for analysis of δ15N in 1992 and δ18O in
1996. δD analyses by quantitative pyrolysis
or High Temperature Conversion (GC-TC
IRMS) was introduced in 1998, together with
the development of the Finnigan DELTAplus XL,
with an energy filter in the m/z 3 collector for
the suppression of 4He+ ions, which otherwise
corrupted the HD+ signal. The Finnigan
GC-C/TC III incorporates the knowledge and
experience that comes with having installed
> 400 GC combustion and > 150 GC pyrolysis
interfaces.
Quantitative Combustion
Quantitative Pyrolysis
Finnigan™ GC-C/TC III
GC Interface for Compound Specific Isotope Analysis
GC Combustion Mode for δ13C δ15N
All compounds eluting from a GC column are oxidized in a capillary reactor to CO2, N2, and H2O at 940 to
1000 °C. NOx produced in the oxidation reactor is reduced to N2 in a capillary reduction reactor. The H2O
formed in the oxidation process is removed by an on-line, maintenance-free water removal system.
For the analysis of δ15N, all CO2 is retained in a liquid nitrogen trap before transfer into the isotope ratio
MS (IRMS) through the movable capillary open split.
The Oxidation Reactor
Quantitative oxidation of all organic
compounds eluting from the GC column,
including the refractory methane, is
performed at temperatures up to 1000 °C.
The reactor consists of a capillary ceramic
tube loaded with twisted Ni, Cu, and Pt
wires.1 The reactor can be charged and
recharged automatically with O2 added to
the Backflush flow every 2-3 days,
depending on the operating conditions.
The Backflush System
The Finnigan GC-C/TC III is equipped with a
Backflush system for eliminating all solvents
in front of the oxidation furnace. The
Backflush reverses the flow through the
oxidation reactor towards an exit directly
after the GC column to cut off all eluting
solvent. All valves are kept outside of the
analytical flow path to ensure the cleanest
combustion conditions and leaving all GC
related parts untouched, thus retaining the
highest GC performance.
1
U.S. Patent 5,432,344
Principle of the Finnigan GC-C/TC III Interface
in GC Combustion Mode
The Reduction Reactor
Water Removal
The LN2 Trap (δ15N Mode)
The reduction reactor is operated at 650 °C
to remove any O2 bleed from the oxidation
reactor and to convert NOx into N2. It is
made of the same capillary design as the
oxidation reactor using the same high
precision, low thermal mass heater.
The water produced by the oxidation
reaction is removed through a 0.3 mm inner
diameter NafionTM capillary, which is dried
by a countercurrent of He. The water
removal adds no dead volume and is
maintenance-free.
For the analysis of δ15N, all the CO2 must be
removed quantitatively to avoid interference
of CO+ (produced in the ion source) with the
N2+ analyte. This is achieved by immersing
the deactivated fused silica capillary
between the water removal and the open
split in a liquid nitrogen bath. The trapped
CO2 is easily released (every 12–18 h) with
no risk of CO2 contamination of the ion
source by using the movable open split.
The Movable Open Split
For high precision isotope ratio determination,
the ion source pressure must be kept
absolutely constant. For this reason, each
continuous flow system has to be interfaced
to the IRMS via an open split. For the
Finnigan GC-C/TC III we have developed a
computer-controlled movable open split,
which couples and decouples to the IRMS
without changing the ion source pressure
while being compatible to the strict
requirements of GC capillary technology.
The valve-free open split is absolutely inert
and does not create any pressure waves.
The open split in decoupled mode allows
maintenance on the Finnigan GC-C/TC III
interface, e.g. release of CO2 in δ15N mode,
without any transfer of sample gas into the
IRMS. During acquisition high backgrounds
can automatically be cut off to place
reference gas pulses, without any effect
to the GC flow system.
Principle of the
Moveable Open Split
Finnigan™ GC-C/TC III
GC Interface for Compound Specific Isotope Analysis
GC Combustion Mode
Determination of 13C/12C Isotope Ratios
Applications:
Alcohols, alkanes, biomarkers, polyaromatics, steroids, FAME, methane and natural gas,
chlorinated hydrocarbons, BTEX, amino acids, sugars, CO2, flavor compounds...
Fatty Acid Methyl Esters (FAME, Standard Mixture), splitless injection, HP5 30m, 0.32 mm, 0.25
µm film thickness, oxidation @ 940 °C, reduction @ 650 °C
Determination of 15N/14N Isotope Ratios
Applications:
Amino acids, flavors, amines, biomarkers, N-heterocycles, drugs, N2, N2O...
N-Acetyl, amino acid propyl esters (NAP), splitless injection, Ultra2 50m, 0.32 mm,
0.52 µm film thickness, oxidation @ 980 °C, reduction @ 650 °C
High Temperature Conversion Mode
Determination of D/H Isotope Ratios
Applications:
Alcohols, alkanes, biomarkers, polyaromatics, steroids, FAME, methane and natural gas,
BTEX, amino acids, sugars, flavor compounds...
Alkanes (standard mixture), spliltess injection, CP-Sil8 CB low bleed 30m, 0.25 mm,
0.25 µm film thickness, high temperature reactor @ 1420 °C
Determination of 18O/16O Isotope Ratios
Applications:
Alcohols, sugars, flavor compounds, phenols...
Flavor mixture of 5-nonanone, g-octalactone, methyl salycilate, linalyl acetate, split injection 1/20, Ultra1 30m, 0.32 mm, 0.52
µm film thickness, Pt shielded high temperature reactor @ 1280 °C
Finnigan™ GC-C/TC III
GC Interface for Compound Specific Isotope Analysis
High Temperature Conversion Mode δD and δ18O
Quantitative pyrolysis by high temperature conversion of organic matter for the conversion of organic O and
H to CO and H2 for δD or δ18O determination requires an inert and reductive environment at very high
temperatures, to prevent any H or O containing material from reacting or exchanging with the analyte.
For δD and δ18O determination, a high temperature reactor is mounted in parallel to the combustion reactor.
Because quantitative conversion is achieved in the reactor, no additional clean up is required. The H2 and
CO are passed through the inactive reduction reactor. The water removal step has no effect on the very dry
analyte gas. The downstream part of the interface is kept in standby.
The Shielded CO Reactor
For the determination of δ18O, the analyte
must not contact the ceramic tube which is
used to protect against air, and for stability.
The pyrolysis takes place in an inert
platinum inlay. Due to the catalytic
properties of the platinum, the reaction can
be performed at 1280 °C. Depending on the
number of C, O and H atoms in the
molecule, CO and H2 plus a C deposit are
formed. Although all organic structures can
be converted with good GC performance
and precision, some compounds show an
offset, which requires internal referencing
by compounds with a known isotope ratio.
Principle of the GC-C/TC III Interface in
High Temperature Conversion Mode
Principle of
High Temperature Conversion
H2
C n H x Oy
C
CO
The High Temperature H2 Reactor
For the determination of δD from organic
compounds, the reaction is performed in an
empty ceramic tube at 1450 °C. Tests have
shown that such high temperatures are
required to ensure quantitative conversion.2
The use of a catalyst must be avoided to
eliminate the risk of adsorption of H2, which
would lead to temperature dependent
2
T. Burgoyne and J. M. Hayes, Anal. Chem. 70, 5136
(1998)
Principle of
Reference Gas Injection
fractionation. The Finnigan GC-TC reactor
is catalyst-free and therefore eliminates
fractionation during high temperature
conversion. Even CH4 can be converted with
completely reproducible and linear results.
Reference Gas Injections
In IRMS, measurement of isotope ratios
requires that sample gases be measured
relative to a reference gas of a known
isotope ratio. This is the only way to
achieve the required high precision of e.g.
< ± 1.5 ppm of 13C (0.15 ‰ in the δ -notation).
For the purpose of sample-standard
referencing, a cylinder of calibrated
reference gas (H2, CO2, N2, CO) is used for
extended periods of time. An inert fused
silica capillary supplies the reference gas in
the µL/min range into the miniaturized
mixing chamber, the Reference Gas
Injection Port. Under control of Isodat 2.0,
this capillary is lowered into the mixing
chamber for 20 s, creating a mixture of
He and reference gas, which flows into
the isotope ratio MS via a second gas line.
This generates a rectangular, flat top
gas peak without changing any pressures
or gas flows.
The use of reference gases reduces the
operational costs while increasing the
sample throughput. The reference gas
consumption is negligible and thus gases
can be kept trickling continuously, ensuring
constant conditions in the supply lines and
pressure regulators.
Finnigan™ GC-C/TC III
GC Interface for Compound Specific Isotope Analysis
Options
Capillary Gas Chromatograph
The Finnigan GC-C/TC III Interface is
equipped with Thermo’s Finnigan Trace GC
with split/splitless injector and digital
pressure and flow control (DPFC). The
Finnigan Trace GC can be equipped with
up to 2 injectors and 2 detectors and
sub ambient oven cooling. Alternatively,
the Finnigan GC-C/TC III Interface can be
interfaced with an Agilent 6890 GC.
GC Injectors
The split/splitless injector offers the flash
evaporation in an inert chamber with split
or total sample transfer onto the capillary
column. The design of the vaporization
chamber ensures wide linearity even with
relatively large sample sizes.
The unmatched Finnigan Trace GC
cold on-column injector gives access to a
discrimination and thermal degradation
free sample introduction directly into the
capillary column with highest
GC performance.
The Finnigan BEST PTV offers
programmable temperature vaporizing
injection techniques. The injector can be
operated in cold split, cold splitless,
solvent split, as well as conventional
isothermal split/splitless mode.
The Finnigan Trace GC’s Large Volume
Injection (LVI) technique combines the
advantages of a cold on-column injection
with sample volumes of up to 250 µL using
a special pre-column and splitting valve in
front of the analytical capillary column.
GC Detectors
The Finnigan Trace GC offers a wide range
of detectors, e.g., Flame Ionization Detector
(FID) and Pulsed Discharge Detector (PDD).
The detector trace is monitored by
Isodat 2.0 software.
Autosamplers
All injection modes can be automated by
using one of the following autosamplers.
The Finnigan AS2000 and AS3000 are
used for all liquid injection modes with a
liquid sample tray for 90 samples. The
Finnigan AS2000 and AS3000 are fully
integrated into the Trace GC concept.
The GC-PAL offers liquid and gas
headspace injections. The GC-PAL has a fully
object oriented structure which allows free
designing and positioning of sample trays.
The Combi-PAL offers all advantages of
the GC-PAL. In addition the Combi-PAL is
upgradeable to heated headspace and solid
phase micro extraction (SPME) injection
techniques.
Integrated quadrupole MS
The conversion of the compounds into
simple gases like H2, CO2, N2 or CO is
mandatory for the high precision required
for compound specific isotope ratio analysis.
Subsequently any direct structural
information of each compound is lost after
this conversion. The integration of
a quadrupole mass specific detector
together with the Finnigan GC-C/TC III
interface allows the parallel acquisition of
structural information and high precision
isotope ratio determination within a single
GC analysis.
GC/GC-C/TC IRMS
Very complex compound mixtures in a
GC sample may not be fully separated on
a single GC capillary column. The coupling
of two GC columns in the Finnigan Trace GC
by the Finnigan MCSS (Moving Column
Stream Switching) system gives access to
the pre-separation of compound groups on
a first GC column followed by a final high
performance separation of a selected
compound group on the second GC column.
A second injector and two FID detectors are
required.
Finnigan PreCon
Trace Gases
Loop Injector
Beside the standard split injection of gas
volumes < 250 µL the Finnigan GC-C/TC III
interface can optionally be equipped with
a Gas Loop Injector with variable loop size
for quantitative sample transfer for low gas
concentrations, e.g. CO2 from air (360ppm),
CH4 in mud gases (< 0.1%).
For gas concentrations in the low ppm and
ppb range the Finnigan PreCon gives access
to the fully automated preparation and
pre-concentration of trace gases like N2O
(300 ppb), CH4 (1.7 ppm), etc. followed by
a cryogenic focusing in front of the
GC column. The Finnigan PreCon can be
loaded manually or operates fully
automated using the GC-PAL autosampler
with a two line needle for continuous
sample transfer. The GC-PAL can be
equipped with a 96x10 mL sample tray.
User-defined sample trays can easily be
registered and automated due to the fully
object oriented structure of the GC-PAL. All
processes are controlled by user-definable
Isodat 2.0 scripts.
For additional information please contact your local Thermo Electron specialist
and get in contact with our team of application specialists.
Finnigan™ GC-C/TC III
GC Interface for Compound Specific Isotope Analysis
Isodat 2.0 Software
Isodat 2.0 is a new software suite for system control, data acquisition and data evaluation.
The advantages Isodat 2.0 offers for Finnigan GC-C/TC III applications include:
• Easy and fast method and
sequence setup for Isotope
Ratio MS, GC and autosampler.
• Complete control and
automation of all interface
functions during data
acquisition.
• Automated GC peak and
background detection with a
wide selection of dedicated
detection and background
subtraction algorithms.
• Fully automated correction of
the GC elution shift of
isotopomers.
• Fully automated H3+ correction
of each single raw data point.
• Fully automated ion correction
for isobaric ion contribution
such as 12C17O16O on 13C16O16O.
• User defined ion correction
formulas can be registered in
Isodat 2.0 using the Isodat
Script Language (ISL).
• Full access to all raw data and
processed data.
• Full access to ion correction
algorithms and intermediated
data.
• Raw data integrity and sample
identity.
• Access to easy batch
reprocessing, manual peak and
background definition including
printouts and data export.
• Fully customizable and
multiple exports of evaluated
data to Excel other
spreadsheet programs and
databases (LIMS).
• All printouts are fully
customizable due to object
oriented printout templates
using the unique Isodat 2.0
Result Workshop package.
• Full network compatibility with
direct and fast access to
Windows® tools.
• Complete Isodat 2.0 system
backup and retrieval within
minutes using the Isodat 2.0
Version Handler.
Based on the unique “Plug and Measure”
concept of the new generation of Isotope
Ratio MS (Finnigan DELTAplusXP,
Finnigan DELTAplusAdvantage and
Finnigan MAT 253), the Finnigan GC-C/TC III
interface is immediately recognized and
operational.
Straight
forward & Easy
Flexible & Powerful
Finnigan™ GC-C/TC III
GC Interface for Compound Specific Isotope Analysis
Analytical Performance
Finnigan GC-C/TC III Basic Performance
10 pulses of reference gas (amplitude 3V, for H2 5V) δ notation
CO2
N2
CO
H2
C
N
18
O
2
H
13
15
Precision (1σ)
Linearity
0.06 ‰
0.06 ‰
0.15 ‰
0.50 ‰
0.02 ‰ / nA
0.02 ‰ / nA
0.04 ‰ / nA
0.20 ‰ / nA
External precision for isotope ratios C, N, O, H
using the GC-C or GC-TC reactors, analyte on column, (n=5), δ notation
13
15
18
C/12C
N/14N
O/16O
D/H
FID MIX
0.03% of n-C14, n-C15, n-C16
in isooctane 0.8 nmol C (10ng)
e.g. 50 pmol n-C15 (11 ng)
Caffeine
750 pmol (200 ng)
1.5 nmol N2 (42ng)
Vanillin
1.7 nmol (200 ng)
5.0 nmol O (80ng)
FID MIX
0.03% of n-C14, n-C15, n-C16
in isooctane 15 nmol H2 (30ng)
940 pmol n-C15 (200 ng)
as CO2
0.2 ‰
as N2
0.5 ‰
as CO
0.8 ‰
as H2
3.0 ‰
Mass spectrometer:
Finnigan DELTA series or Finnigan MAT 253 / MAT 252
Installation Requirements
Thermo has designed its Finnigan GC-C/TC III interface to connect a Finnigan Trace GC to any Thermo
stable isotope ratio mass spectrometer equipped for on-line analysis. Differential pumping of the He gas
load is required for highest precision and sensitivity analysis.
Gases
Acceptance test
Literature
High purity helium can be taken from the GC
carrier gas supply. The Finnigan GC-C/TC III
interface must be supplied with high purity
O2 of 99.996 % grade (or better) for GC
combustion and with 1 % of H2 in He for
GC high temperature conversion on δ18O
determination.
Reference gases (CO2, N2, CO, H2) with
pressure regulators are required respectively.
To use the Finnigan GC-C/TC III with
CO and H2 reference gas, the laboratory
must be equipped with a CO and H2
detector according to local requirements.
A single test series for the precision of
isotope ratios according to the above
analytical performance specifications will be
performed for each mode during the
installation of the Finnigan GC-C/TC III
interface. In combustion mode a C or N test
series and in high temperature conversion
mode a D or O test series will be performed.
For the general purpose GC interface
(Finnigan GC/GP) without furnaces the
specification according to the attached
preparation device will be shown. In any
case the basic interface performance is
shown using one of the listed gases.
For publications, technical information and
application flash reports please contact your
local Thermo Electron specialist.
More information is also available on
our website www.thermo.com.
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BR30033_E 06/04C