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

1

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

4

• 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

7

Equal run 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

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

0

0.2

0.4

0.6

0.8

1

1.2

8

Equal run 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

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

9

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

0.4

0.6

0.8

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)

10

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

0

0.2

0.4

0.6

0.8

1

1.2

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

13

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