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Simply Smart: The Hydrogen Sensor for Chromatographic Systems
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Simply Smart: The Hydrogen Sensor for Chromatographic Systems


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Eliminate the risks in using Hydrogen as a Carrier Gas in GC Analysis. …

Eliminate the risks in using Hydrogen as a Carrier Gas in GC Analysis.

Hydrogen is widely considered to be the best carrier gas for gas chromatography systems. In fact, ASTM subcommittee D0.204 for Hydrocarbon Analysis strongly recommends hydrogen as the de facto choice for GC laboratories. Other advantages of hydrogen include rapid analysis, greater efficiencies, decreased costs and extended column life. The reasons for choosing hydrogen are undeniable—if you take the correct measure to protect your lab from hydrogen leaks.

The ability to safely detect hydrogen leaks in the GC oven is critical to any laboratory using hydrogen as a carrier gas. The new DVLS3 H2 Sensor ensures the safe use of hydrogen in GC analysis. It does this by constantly monitoring the H2 concentrations in the GC oven and automatically switching to an inert gas when typically 25% LEL is reached; this important feature eliminates the risks and at the same time ensures safety.

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  • 1. Simply Smart: The Hydrogen Sensor for Chromatographic Systems The DVLS3 Simply Smart Hydrogen Sensor
  • 2. Content§  Four reasons for using H2 as a carrier gas§  Safety measures§  Hydrogen sensor§  Principle of operation and measurement§  Hardware overview§  Calibration and maintenance§  Summary§  Questions
  • 3. Reasons for using H2 as a Carrier Gas1.  Fast Analysis: §  Fast diffusion rate; 4 times faster than N2 §  Half as viscous as helium; higher linear gas velocity and shorter retention times2.  High Efficiency: §  Flattest Van Deemter curve
  • 4. Reasons for using H2 as a Carrier Gas3.  Prolonged Column Life: □  Some applications have a lower elution temperature, therefore the column life is longer4.  Cost effective: □  3x’s less expensive than its helium equivalent □  Bottle or generator
  • 5. Reluctant to use H2 as a Carrier Gas?§  Hydrogen is an Explosive Gas: Undetected gas leaks can lead to an explosion in the GC oven§  LEL of hydrogen in Air is at 4%
  • 6. Safety measures§  Monitor hydrogen usage§  Safety measures in GC hardware □  Safety Shutdown: when gas pressure set points are not met, the valve and heater are shut off to prevent explosion □  Flow Limiting Frit: if valve fails in open position, inlet frit limits the flow □  Oven ON/OFF Sequence: Fan purges the oven before turning on heater to remove any collected H2 □  Explosion Test: GC designed to contain parts in case of explosion§  Hydrogen sensor in the oven or valve box
  • 7. Principle of Operation Hydrogen Sensor§  Catalytic combustion by catalytized resistor or “pellister”§  Surface of the pellet acts as a catalyst when hot§  Exothermal oxidation of flammable gases ú  2 H2 + O2 → 2 H2O(g) + heat§  Temperature rise results in a change in the electrical resistance
  • 8. Principle of Measurement Hydrogen Sensor §  Compensator pellet is identical but without catalyst §  Compensator pellet removes the effect of environmental factors §  Measurement circuit: a Wheatstone Bridge8 13 March 2013
  • 9. Gas sensitivityHydrogen Sensor
  • 10. Typical Zero Offset drift with Temperature Hydrogen Sensor
  • 11. Typical long term zero offset drift Hydrogen Sensor
  • 12. Typical long term gas sensitivity drift Hydrogen sensor
  • 13. Hardware overview for a Hydrogen Sensor for GC applications
  • 14. Sensor installed in the GC Oven Transfertube through the oven wall to ensure a stable temperature
  • 15. Automatic Switch to NitrogenAfter 1% H2 detection, the carrier gas supply isswitched to nitrogen. The system will maintain aflow through the column.
  • 16. Automatic Stop Signal to GCAfter 1% H2 detection, the sequence will stop afterthe analysis. No waste of analyses or sample.
  • 17. Alarm messagesAfter 1% H2 detection a choice of alarm signals:§  Acoustic alarm§  Optical alarm (blinking display)§  SMS alarm message 17
  • 18. Calibration & Maintenance§  Zero Point Calibrated Using Air§  Alarm level Calibrated using Calibration Mixture§  Yearly or after maintenance or repair
  • 19. Summary (1)§  Catalytic Pellistor gas specific sensor, linear range of 0-2% H2 (0-50% LEL)§  Unaffected by humidity, stable output for long periods, more resistant to shocks and vibrations.§  Expected lifetime: over five years§  Long term stability drift sensitivity: less than 2mV§  User defined alarm: optical, acoustic and/or SMS up to 50% LEL
  • 20. Summary (2)§  Instrument readings: provide real time sensor readings with alarm levels, channel states§  Valve : High pressure 3 way solenoid valve§  Oven operating temperature: up to 450◦C§  Multiple Sensors: Max 4 sensors individually controlled§  Sensor options: temperature, barometer, level, oxygen or hydrogen as a leakdetector.