Gas chromatography analysis requires high purity compressed gases. The three Gas Chromatographic gases commonly used are:
Inert Carrier Gas – Helium or Nitrogen
Fuel Gas – Hydrogen (FID operation)
Combustion Support Gas – Air (FID operation)
The Gas Chromatographic gases are supplied in compressed gas cylinders which are colour coded and require careful handling to prevent accidents. Air and inert gases do not pose major hazards, except accidents that could result from careless handling.
In addition to its use as a combustion gas hydrogen is an ideal choice as a carrier gas . However,its use requires special precautions as it can pose flammability hazards.
- Adequate ventilation must be provided in storage area to prevent formation of combustible air- hydrogen mixtures
- Hydrogen gas cylinders should be kept outside the laboratory in a covered shed to protect from sunlight and rain
- All hydrogen couplings should be regularly checked for leaks
- Most important before turning on hydrogen first ensure that the column is fitted inside the column oven and all connections are leak free otherwise hydrogen concentration can build up and explosions can result due to high temperature inside the oven
- Before removing the column ensure that hydrogen supply has been turned off
Safe Handling of Gas Cylinders
- Do not store cylinders in stairways, near the elevators or entrance to the laboratory
- Compressed gas cylinders should be kept away from heat sources and in any case not subjected to temperatures exceeding 50°C
- Gas cylinders should not be kept in the vicinity of combustibles, fuel oil or even empty waste paper cartons
- Cylinders should be kept upright and fastened securely with a chain to the wall or a laboratory bench
- Connecting gas lines should not cross passages to prevent damage or tripping by those who cross them. Wall mounting with proper colour coding is recommended
- Cylinders should be moved after fastening inside hand held trolleys in vertical position and with safety caps fixed. Under no circumstances should cylinders be rolled on the floor
- Always use regulators, hose connections and tubings which are approved by the equipment supplier
- A flashback arrestor must be used when working with flammable gases.(such as Hydrogen & Acetylene). In the event, a fire propagates through the hose the arrestor will stop the fire from reaching the tank.
- Never use oil orca grease on or around oxygen cylinders, valves, fittings or regulator as it may cause fire or explosion.
- Cylinders with neck threads should have a cap in place over the valve. Remove the cap by hand. Never use a screwdriver, crowbar, or other leverage device to remove the cap
- Read the cylinder label to confirm the gas received is the gas purchased. Never identify the product by the color of the cylinder.
- It is equally essential to keep a regular check on pipes, hoses and connectors leading to the instrument. These should be free of kinks or damage. Perform regularly leak checks on all joints and seals
- On completion of analysis close all cylinder valves and allow the residual gas to bleed before turning off the exhaust vent
- Never keep empty and filled gas cylinders in same. areas
- Do not store cylinders in spaces where they can come in contact with live wires as this can cause electric shocks.
- Non compatible gases such as hydrogen and oxygen should not be stored in a common storage area as these can form explosive mixtures
- Fire extinguishers should be provided in area storing combustible gases and these should be checked periodically
Gases do not pose major hazards when safety precautions are exercised. Always remember you are responsible for your safety and also safety of your laboratory co-workers.
Please do offer your suggestions and comments based on your personal experiences.
Acknowledgement:The author wishes to thank Mr Girish Kulkarni for his valuable inputs which have been included in the article.