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Innovative Alternatives to Dual Inlet Bellows for Reference Gas Management in IRMS

This document explores an alternative approach to handling reference gases in isotope ratio mass spectrometry (IRMS), particularly for the analysis of noxious gases such as CO and CH3Cl. The Thermo Conflo IV system is highlighted as an adaptable solution, allowing for the precise management of ref gas flow rates, which can vary from 0.2 mL/min to much lower rates. The study discusses necessary modifications for safe gas handling, including the conversion of AgCl to CH3Cl and the challenges posed by using high-cost, toxic gases. Overall, the findings suggest that the Conflo IV method enhances efficiency and reduces gas consumption.

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Innovative Alternatives to Dual Inlet Bellows for Reference Gas Management in IRMS

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  1. Noxious Gases Ref Peaks:An Alternative to Dual Inlet Bellows Paul Eby

  2. Normal Conflo Ref Gas Ref Gas He GC / EA - Ref Gas is always flowing (0.2mL/min) - Not okay for noxious gases - CO, CH3Cl, SO2 IRMS - Small quantities / expensive gases

  3. REF SAMPLE IRMS Using the Bellows GC / EA - Consumption is very low (0.02 to 0.002mL/min) - Continuously flows - Noxious gas exits with the pump exhaust - Requires dual inlet

  4. 37Cl Measurements • Precipitate chloride out as AgCl by adding AgNO3 • Convert AgCl to CH3Cl gas by reacting with CH3I • Run by GC-IRMS • Measured as CH3Cl Problems Requires an extra cup to measure masses 50 and 52 Bellows needed for toxic CH3Cl (also expensive) $ $ $ $

  5. Thermo Conflo IV Allows for 5 different reference gases, 2 at a time

  6. Thermo Conflo IV Ref A Ref B 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? Ref C IRMS

  7. Thermo Conflo IV in Isodat Extra columns added to the method using Configurator

  8. Carbon Dioxide On/Off Test ave = -0.01 stdev = 0.04 ave = -0.03 stdev = 0.02

  9. Carbon Dioxide On/Off Test

  10. Methyl Chloride Trials • Upgrade the detectors • Add ventilation to the Conflo IV • Pump exhaust vented • Small bomb of CH3Cl

  11. Methyl Chloride On/Off Test ave = -0.02 stdev = 0.02 ave = 0.01 stdev = 0.01

  12. Methyl Chloride On/Off Test

  13. Methyl Chloride On/Off Test

  14. Conclusions • ConFlo IV can be used to limit consumption of ref gas • Comparing to Bellows: • Flow rate in Conflo IV 0.2mL/min • Flow rate in bellows 0.02 - 0.002mL/min?

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