Micro Gas Chromatograph POKE meeting Tallin, Sabrina Schmidt, Laboratory of Industrial Chemistry and Reaction Engineering, Åbo Akademi
Micro Gas Chromatograph
POKE meeting Tallin, Sabrina Schmidt, Laboratory of Industrial Chemistry and Reaction Engineering,
Åbo Akademi
Classical Gas Chromatograph (GC)
•Injection
•Separation
•Detection
Micro-GC Agilent 3000A
Micro-GC : Elements
Each element contains:
Micro-injector
Sample column (+pre column)
Reference column
Detector
Electronic pressure control
Gas flow solenoids
Hardware
Control board
The portable module
• Delivered also as portable module with a battery
and an inbuilt gas-cylinder
For workers/rescuers in coal mines
• Coal mine explosion: indicated by C2H6, C2H4 and C2H2.
• Micro GC can analyze these compounds in less than 60 seconds at the necessary detection limit of 1ppm
General features
• Mobile
• Modular setup, easy exchange of column types
• Online analysis with programmable sampling intervals
• Very fast analysis, typically less than 180 s
General features
• Fixed/variable volume injector
• Back flush: removes unwanted contaminants from your analysis
• Thermal conductivity detector: 10 times more sensitive than traditional TCDs, allowing you to detect common gas components in the low ppm range.
General features: Precautions
• Only for clean gas samples Micro injector is sensitive towards plugging
• No liquids, no condensibles
• No particles
• Agilent supplies sample filters and conditioners
• Gas liquid separator
• Pressure reducer
Our micro GC
• Four separate modules
• Self-made valve system to connect two reactor setups and two calibration gases
Columns
• Plot U: hydrocarbons, CO2, air/CO, water, polar compounds
• OV-1: Hydrocarbons, phenol, amines, non-polar
• Alumina: petrochemicals (acetylene, ethylene, propadiene)
• Molesieve 5A : Hydrogen, CO, oxygen, nitrogen, methane
Two practical examples from our lab:
Online Analysis
Example 1: Online analysis for methyl chloride synthesis
Analysis of methanol, dimethyl ether, methyl chloride
No liquids: Lines are heated to 95 °C to prevent condensation of methanol
GC signals and analysis time
13
• Sample analysis in less than 1 min
• Separation is not optimal
PlotU
OV-1
Stability of methanol flow
14
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0 200 400
Are
a /
µV
*s*1
06
flow
stop
t/min
•Standard deviation from average flow: 1.6 %
•Fixed injection volume is reliable: easy calibration
•Information on residence time distribution
Switch to standard GC due to breakdown of micro GC
Analysis using a standard GC
Separation: +
Sample analysis : - (10 min instead of 1 min)
Sampling: - (running from the reactor to the GC with a gas tight
syringe heated to 100 °C)
Maintenance: - (septum of reactor sampling unit and GC)
Standard GC is sufficient
Micro GC vs. normal GC
Example 2: Aqueous phase reforming of sugar alcohols
Analysis of CO, CO2, H2 , CH4, linear hydrocarbons C1-C4,
He, N2
All analyzed in one sample/run
Inert gas: 1 wt% He in N2 as internal standard for micro GC
Analysis works perfectly – No change in signal since four years
Summary: Advantages /Disadvantages
• Modular Design: Column, Injector and Detector in a box
No possibility to self-repair
• Micro injector is delicate! Micro injector was plugged
– The whole module has to be replaced
• Mobile
• Online analysis
• Easy calibration due to fixed injection volume
• Parallel analysis with four columns
Thank you for your attention!