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Test method for Acetone and Ethanol in Methanol
Scope
This method covers the determination of acetone and ethanol at the ppm level, volume basis in pure methanol.
Summary
The sample is injected into and carried through a single, packed, gas-liquid partition column with a carried gas (nitrogen / helium). The separated components in the effluent are measured by flame ionisation detector and recorded on a chromatogram. The concentration of the components are determined by measurement of the peak areas and comparison with a calibration mixture, alternatively by linking the potentiometric recorder to suitable integrator / calculator.
Significance and Use
No interfering substances have been detected in refined methanol. If present, n-propanol n-butanol could interfere with the resolution of ethanol.
Apparatus and Reagents
 | Gas chromatograph with FID detector.
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| Computing integrator / Printer
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| Methanol AR grade
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| Ethanol AR Grade
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| Acetone AR Grade
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| 10 Microlitre Syringe.
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| Column: 610 em (20ft.) of stainless steel tubing with 33 weight % D-sorbitol on 80 to 100 mesh, acid-washed "Chromosorb" P. |
Chromatographic conditions
Carrier Gas - Nitrogen = Pressure 3.6 bar.
Flame - hydrogen = pressure 1.5 bar.
Air (dry) = pressure 1.8 bar.
GC attenuation - x 1
Range - x 10
Sample size - 4 u 1
Over temperature - 100 Deg C.
Detector Temperature - 110 Deg C.
Injector Temperature - 110 Deg. C.
Procedure
Inject 4 ul of AR grade methanol (carbonyl free methanol). Measure the area of the acetone and ethanol peak produced. Fill a 100 ml. volumetric flask with this pure methanol and add 1 ul of acetone and 1 ul of ethanol AR grade and mixed. This mixture will now contain an additional 10 ppm of acetone and ethanol. Inject 4 ul of this mixture under identical chromatographic condition.
Subtract the areas of acetone and ethanol peaks in AR grade methanol from the corresponding peak area in this mixture. The difference in areas will be equivalent to 10 ppm. Determine the response factor F by dividing concentration in ppm by corresponding peak area.
Now inject 4.0 ul of product methanol under identical chromatographic condition. Note the area of acetone and ethanol peak.
Calculation
Acetone / Ethanol ppm = F x A.
Where F is the response factor and A is the area of corresponding peak. |
