modernizing isothermal gas chromatography for …...modernizing isothermal gas chromatography for...
TRANSCRIPT
Modernizing Isothermal Gas
Chromatography for Process
Analysis
Ryan B. Wilson, Jeremy S. Nadeau, Jamin C. Hoggard, Robert E. Synovec,
Department of Chemistry, Box 351700, CPAC, University of
Washington, Seattle, WA,98195
CPAC Summer Institute
July 21, 2011
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Outline
• Isothermal Process GC
• Improving the appearance and detection limits of isothermal separations via TIBS
• Monitoring aqueous systems with high sensitivity
Outline
• Isothermal Process GC
• Improving the appearance and detection limits of isothermal separations via TIBS
• Monitoring aqueous systems with high sensitivity
Process Gas Chromatography
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• Optimize chemical information per time
Optimize total peak capacity and peak capacity
production
• High Throughput
On-line or at-line analysis
Fast analysis time
• Sub minute to sub second time scale
• “GC Sensor”
• Robust instrumentation
Minimal requirements for power, maintenance, etc.
DARPA Panoptic Analysis of Chemical Traces (PACT) Project
• Automated, high-throughput analysis of atmospheric sampling efforts aimed at producing exhaustive chemical maps of the environment
• Potential uses
– Military
– Anti-terrorism
– Environmental Studies
Chemical Identification for Surveillance and Tracking (ChemIST)
• Includes several MS instruments, a mid-IR instrument and high speed GC-MS/FID/TCD
• Goals
– Phase 1: 100 samples/day 5 min separation time
– Phase 2: 125 samples/hour 44 s separation time
– Gen 1: 300,000 samples/day 250 ms separation time
• Design GC to minimize required power and consumables
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Equal run time (250 ms), unit resolution between adjacent peaks
0 0.05 0.10 0.15 0.20 0.25
0
0.2
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1.2
Time (s) Time (s)
Rela
tive S
ignal
110 °C 110 °C
140 °C
240 °C/s
wb peak 1 = 5 ms wb all peaks ~ 5 ms
Isothermal (left) vs Temperature Programmed (right) for 1 m x 100 µm column (simulated from real isothermal data)
Gross, G. M. Prazen, B. J. Grate, J. W.; Synovec, R. E. Analytical Chemistry 2004, 76, 3517-3524.
Reid, V. R. McBrady, A. D.; Synovec, R. E. Journal of Chromatography A 2007, 1148, 236-243.
0 0.05 0.1 0.15 0.2 0.25
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1.2
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Equal run time (250 ms), unit resolution between adjacent peaks
0 0.05 0.10 0.15 0.20 0.25
0
0.2
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Time (s) Time (s)
Rela
tive S
ignal
110 °C 110 °C
Isothermal Advantages
140 °C
240 °C/s
Must cool
column before
next injection
No heating or
cooling
simplifies the
instrument and
reduces power
consumption
Isothermal (left) vs Temperature Programmed (right) for 1 m x 100 µm column (simulated from real isothermal data)
0 0.05 0.1 0.15 0.2 0.25
0
0.2
0.4
0.6
0.8
1
1.2
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Equal peak separation time (250 ms), unit resolution between adjacent peaks
nc = 40 peak capacity = nc = 17
0 0.05 0.10 0.15 0.20 0.25
0
0.2
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0.6
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1
1.2
Time (s) Time (s)
Rela
tive S
ignal
110 °C 110 °C
Isothermal Shortcomings
240 °C/s
140 °C
Isothermal (left) vs Temperature Programmed (right) for 1 m x 100 µm column (simulated from real isothermal data)
0 0.05 0.1 0.15 0.2 0.25
0
0.2
0.4
0.6
0.8
1
1.2
Isothermal (left) vs Temperature Programmed (right) for 1 m x 100 µm column (simulated from real isothermal data)
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Equal peak separation time (250 ms), unit resolution between adjacent peaks
0 0.05 0.10 0.15 0.20 0.25
0
0.2
0.4
0.6
0.8
1
1.2
Time (s) Time (s)
Rela
tive S
ignal
Lower signal
for late eluting
peaks
Higher signal for late eluting peaks
110 °C 110 °C
Isothermal Shortcomings
240 °C/s
140 °C
0 0.05 0.1 0.15 0.2 0.25
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Outline
• Isothermal Process GC
• Improving the appearance and detection limits of isothermal separations via TIBS
• Monitoring aqueous systems with high sensitivity
• Computational method to address the General Elution Problem
– Transforms the raw isothermal data into a constant peak width domain
• Resulting chromatogram appears to have been collected with a temperature program
• Increases S/N of later eluting peaks
• Useful in field and process GC situations
• Nadeau, J. S. Wilson, R. B. Fitz, B. D. Reed, J. T.; Synovec, R. E. Journal of Chromatography A 2011, 1218, 3718-3724.
Temporally Increasing Boxcar Summation (TIBS)
0 20 40 60 80 100 0 20 40 60 80 100
200
500
0
100
300
400
600
TIBS on Model Data
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Model Isothermal Chromatogram, Rs = 1
Column: DB-5, 1 m x 100 μm, df = 0.4 μm Temperature: 65 °C to = 240 ms nc = 40
wb (
pts
)
Retention factor
Fit a line to the widths
over the time range
Sum 50 points
of data
Time (ms)
Sign
al, A
rbit
rary
Sca
le
0 10 20 30
0 100 200 300 400
Sign
al, A
rbit
rary
Sca
le
Data Points
Collect Data Step A
Baseline Correction Step B
Calculate wbox(k) Step C
Apply Linear Boxcar Step D
Calibration?
Yes
No
TIBS Flow Chart
0 5 10 15 20 25
0
0.5
1
1.5
2
2.5
3
3.5
4
1 X
20 Y
5 X 0.2
Y
FID
Sig
nal
Retention Time, s
Isothermal Chromatogram prior to TIBS
0 20 40 60 80 100
0
10
20
30
40
50
0 20 40 60 80 100
0
0.5
1
1.5
2
2.5
3
Wb, s
k
Wb
ox , p
oin
ts
Calibration: Boxcar Size vs. Retention (k)
Boxcar Size = 1
S/N is unchanged
Boxcar Size = 50
S/N ~ 7 fold higher
0 5 10 15 20 25
0
2
4
6
8
10
12
Sum
med
Sig
nal
Retention Time, s
Before
Isothermal Chromatogram after TIBS
Isothermal Chromatogram after TIBS In point domain, looks like temperature program
0 100 200 300 400
0
2
4
6
8
10
12
Sum
med
Sig
nal
Retention Time, points