Noxious Gases Ref Peaks:An Alternative to Dual Inlet Bellows

Paul Eby

Normal Conflo Ref Gas

GC / EA

Ref Gas

He

IRMS

- Ref Gas is always flowing (0.2mL/min)

- Not okay for noxious gases

- CO, CH3Cl, SO2

- Small quantities / expensive gases

Using the BellowsGC / EA

- Consumption is very low (0.02 to 0.002mL/min)

- Continuously flows

- Noxious gas exits with the pump exhaust

IRMS

REF SAMPLE

- Requires dual inlet

37Cl Measurements

1. Precipitate chloride out as AgCl by adding AgNO3

2. Convert AgCl to CH3Cl gas by reacting with CH3I

3. Run by GC-IRMS

4. Measured as CH3Cl

ProblemsRequires an extra cup to measure masses 50 and 52

Bellows needed for toxic CH3Cl (also expensive)

$ $ $ $

Thermo Conflo IV

Allows for 5 different reference gases, 2 at a time

Thermo Conflo IV

Ref A

Ref B

Ref C

IRMS

Can we leave the ref gas off until a peak is needed?

Does the gas need to reach a steady state by constantly flowing?

How long does it take to reach a steady state?

Can I test this before upgrading the IRMS?

Thermo Conflo IV in Isodat

Extra columns added to the method using Configurator

Carbon Dioxide On/Off Test

ave = -0.03 stdev = 0.02 ave = -0.01 stdev = 0.04

Carbon Dioxide On/Off Test

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

1 2 3 4 5 6 7 8 9 10 11 12

d13C

/ p

erm

il

Methyl Chloride Trials

1. Upgrade the detectors

2. Add ventilation to the Conflo IV

3. Pump exhaust vented

4. Small bomb of CH3Cl

Methyl Chloride On/Off Test

ave = 0.01 stdev = 0.01 ave = -0.02 stdev = 0.02

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

1 2 3 4 5 6 7 8 9 10 11

d37C

l / p

erm

il

Methyl Chloride On/Off Test

Methyl Chloride On/Off Test

Conclusions

1. ConFlo IV can be used to limit consumption of ref gas

2. Comparing to Bellows:

Flow rate in Conflo IV 0.2mL/min

Flow rate in bellows 0.02 - 0.002mL/min?