4103FSBMOL - Practical 5 - GC. Flashcards
Gas Chromatography (GC) - Analysis of Ethanol content in Wine.
What type of column was used?
A Capilliary Column.
How long was the column used?
30 metres.
What diameter was the column used?
0.25mm.
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What is the software used for the GC (and the HPLC)?
Chemstation.
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What percentage of alcohol is the Wine Sample we used?
13.5%.
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What is the Brand of the GC-FID?
Agilent 6890N.
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What column was used on the GC?
DB-WAX-30m x 0.320mm x 0.5µm at 180°C. High polarity, Polyethylene Glycol stationary phase (optimised for Ethanol and Propanol separation).
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What carrier gas and flow rate was used on the GC?
Hydrogen - 3.2ml/minute.
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What temperature was the GC oven set at?
70°C.
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What type of injector was used on the GC?
Split Injector (Agilent 7683B).
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What was the split ratio on the injector for the GC?
50:1.
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What is the inlet temperature for the GC injector?
260°C.
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How much sample was injected into the GC instrument and why? (injection volume).
1µl - so it doesn’t overload the machine.
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What detector was used with the GC?
What temperature was this set at?
A Flame Ionisation Detector (FID).
280°C.
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What is the attenuation of the GC?
64.
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What was the Run Time we used for our samples on the GC?
3.5 minutes.
What does the GC in our practical seperate the sample by?
Boiling Points of the different Components/ components of a volatile mixture by the affinity of each component to the stationary phase.
If the sample has a higher affinity for the stationary phase than the mobile phase, what happens?
Retained for longer leading to a longer retention time.
If the sample has a higher affinity for the mobile phase than the stationary phase, what happens?
The sample will be retained for a shorter length of time on the column.
What is the proper name for the rubber seal that the GC injects into?
Septum.
What does the Split Injector do in the Practical we did?
What do Split-less injectors do?
It instantaneously volatises the material and then allow some of it to be vented off, reducing the amount of sample to reach the column.
All volatised material is injected onto the column.
What is the name of the separation which occurs from the GC oven at a constant temperature?
Isothermal Separation.
What is the name of the separation which occurs from the GC oven at a changing temperature?
Gradient Separation.
What are the 2 types of GC column called?
Capilliary and Packed.
What are the differences between a Capilliary and Packed Column?
- Capilliary - small diameter, long narrow high purity quartz tubing with a thin layer or stationary phase directly bound to the inside walls.
- Packed - metal or glass tubing of usually thicker diameter, packed with small diameter particles coated with a thin layer of stationary phase.
Capilliary Tubing is more effiencent but also more expensive.
How do you classify separated components?
By their Retention Times.
What is on the Axis of a GC Chromatogram?
Concentration (y-axis) and Time (x-axis).
How does a FID work?
A Flame Ionisation Detector works by the carrier gas containing the components being mixed with hydrogen and being burnt. This produces component ions which are collected by an electrode, therefore producing a current.
