1. Continuous Flow Isotope Ratio Mass Spectrometry
Step #1:
Convert organic or inorganic samples into gas…
d13C… CO2
d15N… N2
d2H… H2
d18O… CO
d34S… SO2
GasBench (Thermo)
Elemental Analyzer
(Costech)
Thermal Conversion EA
(Thermo)
Gas Chromatograph-Combustion

2. Conflo & Isotope Ratio Mass Spectrometers (IRMS)
Thermo Scientific
Conflo IV Interface
(Continuous Flow)
Dual Inlet
(Non-Continuous Flow) OR
Step #2:
Introduce gas (e.g., CO2 or N2) into the IRMS…
Thermo Scientific
Delta V Plus
Thermo Scientific
MAT 253

3. Pure Gases via Dual Inlet IRMS
Detector Voltage
3.52
5.58
Detector Voltage
5.58
10-8 mbar
35 mbar
55 mbar
55 mbar
CO2
CO2
Changeover Valves
CO2
CO2
CO2
Reference
Gas
Sample
Variable Volume
High Vacuum Pump
Variable Volume

4. IRMS Universal Interface (ConFlo IV)
SAMPLE
REFERENCE
High Flow
(EA, TC/EA)
Low Flow
(GC-C)
IRMS
10-6 mbars
Reference
Helium
Dilution
Helium
Dilution
CO2
Detector Voltage
0.00
9.85
6.22
CO2

5. Isotope Ratio Mass Spectrometer
Electromagnet
Next, the ions are accelerated
toward an electromagnet
through the flight tube.
The electromagnet
deflects the ions.
‘Light’ ions are deflected
more than ‘heavy’ ions.
First, gas molecules
are turned into ions
in the ion source.
flight tube
Finally, detectors
count the number of
ions for each mass.
heavier ions
lighter ions
Ion+
Ion Source
12C18O16O mass 46
13C16O mass 45
12C16O mass 44
Carbon Dioxide (CO2)
Detectors
12C18O16O
13C16O2
12C16O2
m44
m45
m46
Gas

6. The Source: Ionization and Acceleration
Electron Trap
(0 to +40 V)
Electrostatic Lenses
Magnet Focuses
Electron Beam N
Electron
Beam
Gas Inlet
Gas
Ion+
Ion Beam
Ionization
Chamber
(+3000 V) S
Cathode
(0 to 1.5 mA)
Extraction
(0 to -400 V)
X-Focus
(0 to -400 V)
Slit
X-Deflection
(0 to +100 V)
Y-Deflection
(+200 to +500 V)
Quadrupole
Lens
Electron Source
Forms Ion Beam
Focus Ions on Slit
Guides Ions Toward Detectors
Fine-Tune X and Y
Focal Lengths

7. Ion Deflection (Electromagnet)
Light Ion
Electromagnet
Heavy Ion S
Magnetic
Field N
Flight Tube

8. Ion Detection (Faraday Cups)
Ion Beam
Detector Array
M44
M28
M29/M45
M46
M30 M
M+1
M-1
Detector
Amplifier
Voltage
Frequency
Converter
Counter
Focal Plane
Secondary Electron
Suppression
Ground
Faraday Cup + _
Electron
Source
current, mA e-
Ion+