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Experiments Overview

Gas Chromatography - Determination of Alcohols

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Equipment:
Gas Chromatograph, integrator or recorder, Gas supply of Air, Hydrogen, and Nitrogen, Chromatography column, GC 5ul syringe.

Apparatus:
Volumetric flasks 100ml; Pipettes 1ml, 2ml, 3ml, 4ml, 5ml.

Chemicals:
GC or Pure grade quality Alcohols:
Methanol, Ethanol, Propanol, Butanol.

Sample:
Provide a 40% ethanol sample.
Students will bring their own "spirit" sample.

Sample preparation:

1. Provide pure Methanol, Ethanol, Propanol, and Butanol.
2. Provide three samples, and give a different sample each week.

A = 40% ethanol
B = 30% ethanol
C = 20% ethanol.

Analytical notes:

1. Columns: can use either Carbowax, Porapak Q, PEGA, or PEG 20M.

The PEG 20 M is used for this experiment because it gives very short retention times:
Column temperature = 90°C
Carrier gas = Nitrogen
Combustion = Air and Hydrogen
Flow rate = 30ml per min

2. Check for leaks: Turn on carrier gas and use soap solution and soft brush to wet connections. Check outlet from gas cylinders and all gas line connectors. Check column end couplings, and the injection port for septum damage. If you get bubbles coming out from any one of these areas, you need to tighten it up or replace it.

3. Purge and condition the analytical column for at least one hour before injections.

4. Flush out syringe immediately after each injection with acetone.

Operation of Instrument:

Follow User Guide. Obtain help and advice from Demonstrator or Technician




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