Comprehensive Two-Dimensional Gas Chromatography coupled ...

GACID
Comprehensive Two-Dimensional
Gas Chromatography coupled with Time-of-Flight
Mass Spectrometry
for Broad Spectrum Organic Analysis
GCxGC-TOFMS
GACID -Group for Analytical Chemistry Instrument Development
Harsh Environment Mass Spectrometry workshop
09/22/2003
Sarasota, FL
Stefan Scherer
Department for Atmospheric, Oceanic, and Space Sciences
Space Physics Research Laboratory
University of Michigan
09/23/2005 S. Scherer 1

Presentation Outline
GACID
• Separation using Comprehensive 2-Dimensional Gas Chromatography
(GCxGC)
– 1-D GC versus 2-D GC
• Identification using Time-of-Flight Mass Spectrometry TOFMS
– Capabilities of TOFMS
• Applications for GCxGC-TOFMS (selected examples)
– Tholins
– CWA simulants detection in gasoline
– Breath analysis
• Field deployment at UMBS
• Subsystem development activities
– Thermal Modulator
• Future steps
• Acknowledgement
09/23/2005 S. Scherer 2

1-Dimensional Gas Chromatography (GC)
GACID
Standard 1D-GC technique
narrow sample plug injection
into the chromatographic
column
Sample transport happens in
the mobile phase by the flow
of an inert carrier gas
separation of the sample
occurs along the coated
column with various stationary
phases by interaction of the
sample material with the
column coating
Retention time of the effluent
is detected
09/23/2005 S. Scherer 3

Comprehensive 2-Dimensional Gas Chromatography (GC x
GC)
GACID
09/23/2005 S. Scherer 4

1-Dimensional versus 2-Dimensional Gas Chromatography (1/2)
GACID
1-Dimensional GC
Comprehensive 2-Dimensional GC
I
I
C
C 1
C 2
D
TM
D
TIC (a.u.)
Time (s)
Time (s) in C2
TIC (a.u.)
Time (s) in C2
Time (s) in C1
Time (s) in C1
09/23/2005 S. Scherer 5

1-Dimensional versus 2-Dimensional Gas Chromatography (2/2)
GACID
(a)
(b)
TIC TIC
0
2-Dimensional separation (modulated)
1-Dimensional separation (non-modulated)
1000 2000 3000 4000 5000
Time (s)
(c)
Time (s)
10
5
0
1000 2000 3000 4000 5000
Time (s)
2-Dimensional view of GCxGC
0
0
1000 2000 3000 4000 5000
Time (s)
09/23/2005 S. Scherer 6

Measurement capabilities of GCxGC
GACID
Analysis of organic carbon compounds C 5 to C 25
High peak capacity (several thousand peaks per chromatogram)
Typical analysis cycle duration 30 min
Various sampling methods are available
Solid samples using pyrolysis
(10-100 µg/cycle sample material using Flash or Stepped Pyrolysis)
Volatile samples using direct sampling/pre-concentration
Liquid sampling using split/splitless injection
Sensitivity in the low parts per trillion (ppt) range
Increased detectability
Linearity over more than 3 orders of magnitude (ppb - ppt)
Thermal Modulator (TM) is key component of GCxGC
- commercial TM require consumables
- consumable-free TM under development
09/23/2005 S. Scherer 7

GCxGC-TOFMS
GACID
Inlet
Separation
Identification
Identification by TOFMS
Full mass spectrum with every extraction pulse firing
without necessity of scanning the entire mass range
Repetition rates up to 100kHz achievable, which allows
monitoring fast sample composition changes on time
scales much smaller than milliseconds
High initial energy spread of ions up to several hundred
eV is admissible
Neither static nor dynamic magnetic fields are required
Performance depends mainly on electrical circuits rather than
mechanical alignment
Mass scale calibration for TOFMS is simple and reliable
09/23/2005 S. Scherer 8

Chromatogram of tholins using GCxGC-TOFMS technique (1/2)
GACID
sample (tholin) analyzed by commercial laboratory equipment (LECO
Corp.) using pyrolysis injection (CDS).
09/23/2005 S. Scherer 9

Chromatogram of tholins using GCxGC-TOFMS technique (2/2)
GACID
09/23/2005 S. Scherer 10

Chemical Warefare Agent Simulants in Complex Organic Mixtures
GACID
09/23/2005 S. Scherer 11

Human Breath Analysis
GACID
Human breath analysis
before smoking
Human breath analysis
shortly after smoking
09/23/2005 S. Scherer 12

Commercial GCxGC-TOFMS
GACID
LECO Pegasus 4D
GCxGC – TOFMS
• Resource intensive liquid LN 2 cooled four jet Thermal Modulator
(dewer of LN2 /week)
http://www.leco.com
09/23/2005 S. Scherer 13

GCxGC–TOFMS breadboard using closed-loop air-cooled TM
GACID
GCxGC – TOFMS breadboard
• Custom made pre-concentrator
• Integrated packaged columns (RVM Scientific)
• Custom made closed-loop air-cooled consumable-free TM
• TOFMS (Ionwerks)
09/23/2005 S. Scherer 14

Breadboard results of GCxGC - TOFMS
GACID
09/23/2005 S. Scherer 15

Field deployment of the GCxGC-TOFMS breadboard
GACID
GCxGC–TOFMS breadboard field deployed during summer 2005 campaign
at the PROPHET tower laboratory at the University of Michigan
Biological Station (Northern Michigan); refer to poster from Judy Yu
Measurement Goal: VOCs and isoprene measurements
09/23/2005 S. Scherer 16

2-Stage Thermal Modulator
• Two-Stage Thermal Modulator designed
and prototyped at the
University of Michigan
• Set Industry Standard for Modulators
• Two-Stage will eliminate sweep through
GACID
1 st Stage
2 nd Stage
Drawing Courtesy of Bruce Block – AOSS University of Michigan
09/23/2005 S. Scherer 17

Single Stage versus 2-Stage Thermal Modulator
GACID
Single-Stage Air-Cooled
A
• limited quantitative analysis
• Breakthrough observed
• Peak Tailing as
concentration inside
modulator increases
Two-Stage Air-Cooled
B
• Improved quantitative
analysis
• Minimal Breakthrough
• No Peak Tailing
0 5 10 15 20 25 30 35
Time (s)
1 ppm Octane
09/23/2005 S. Scherer 18

Future of GCxGC using Micro-Fabricated Columns
GACID
• Further miniaturize the separation section
by using MEMS technology for the GCxGC
subsystem
• Decrease physical size as well as reduce
resource requirements with on-chip heating
• Collaboration with the WIMS center at
UofM
09/23/2005 S. Scherer 19

Future of GCxGC using Micro-Fabricated Columns
GACID
3.2 cm
• Capillary length 3m
• Chip size (3.2cmx3.2cm)
• cross section
150 µm wide x 240 µm
deep
• Side ports etched in Si for
more mechanical stability
• Etched back structure for
reduced thermal mass
150 µm
240 µm
Digital Picture of 3-
meter micro fabricated
column
09/23/2005 S. Scherer 20

Future of GCxGC using Micro-Fabricated Columns
GACID
• Separation of series of
n-alkanes (C 5 to C 15 ) at
3 temperature
programs
a) 10 K/min
b) 20 K/min
c) 30 K/min
• Design of a mesoscale
TM using
thermo-electric cooling
and resistive heating
attached to columns in
MEMS technology
09/23/2005 S. Scherer 21

The GACID Team
GACID
… By the enthusiastic effort of the following team members at the
University of Michigan the results have been made possible …
College of
Engineering
Charlie Hasselbrink
Atmospheric,
Oceanic, and Space
Sciences
Hunter Waite
Megan McGuigan
Bruce Block
Stefan Scherer
Chemistry
Richard Sacks
Amy Payeur
PT Stevens
Mark Libardoni
09/23/2005 S. Scherer 22

Pre-Concentrator
GACID
Column one
Stainless Steel Mesh
Beds
Y B X C
Nut
Glass Wool
Gas Flow During Sample Collection
Gas Flow During Sample Desorption
Carbon Molecular Sieve
Graphitized Carbon
Symbo
l
Adsorbent
Carboxen
1000
Carbopack X
Adsorbent
Strength
Application
C Strongest C 2 to C 5
X
B
Y
Carbopack B
Carbopack Y
Stronger
Weaker
Weakest
C 3 to C 5
C 5 to C 12
C 12 to C 20
09/23/2005 S. Scherer 23

Custom designed Thermal Modulator
GACID
Dual stage Thermal Modulator
- resistively heated -air-cooled
09/23/2005 S. Scherer 24

Gas Chromatographic columns
GACID
RVM Scientific integrated columns
Add photo of
the RVM
columns
09/23/2005 S. Scherer 25

Murchinson Meteorite analysis using Pyrolysis-GCxGC-TOFMS
GACID
09/23/2005 S. Scherer 26

Time-of-Flight principle
GACID
U
L in d s
U extr
Time focus
U drift
ion source
1
fieldfree driftpath
reflectron
detector
2
U
L out
d
s
Time focus
L in + L out = L
Mamyrin et al., 1972
09/23/2005 S. Scherer 27

Electron Impact Storage Ion Source
GACID
repeller A
filament
repeller B
extraction grid
A 1
A 2
lens
drift
simulated peak
backplane
Dt tat
3 ns
Dt eds
< 1 ns
∆t
turn-around time
tat
( m)
= 2⋅
2mU
q E
extr
0
trap
1. Time focus
501 504
TOF [ns]
U
U extr
z
U drift
09/23/2005 S. Scherer 28

Orthogonal Extraction Ion Source
GACID
anode
filament
extractor
entrance lens
skimmer
trap
extraction grid
A1 A2 lens drift
simulated peak
backplane
Dt pbd
2 ns
Dt eds

09/23/2005 S. Scherer 30
GACID

Thermal Modulators: Overview of techniques
GACID
P.S.
N 2
gas
J.B. Phillips - 1991
E.B. Ledford and J. Beens - 2000
J.B. Phillips - 1993
P.J. Marriott - 1997
E.B. Ledford - 2002
09/23/2005 S. Scherer 31