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How to Check for Ether in Methanol

Diethyl ether and methanol are two of the various solvents organic chemists use in the lab. If you have a sample of methanol and want to test it to determine if it contains diethyl ether, the safest and most effective approach is gas chromatography or GC. In GC, a nonreactive carrier gas like helium forces a small amount of vaporized sample through a column. Depending on how they interact with the liquid coating in the column, some substances will exit more rapidly than others, and you can use the difference in retention time to distinguish them.

Things You'll Need

  • Gloves, chemical safety goggles and lab coat
  • Gas chromatograph
  • Micro GC syringe
  • "Rinse" vial containing diethyl ether
  • "Standard" vial containing 1:1 mixture of diethyl ether and methanol
  • "Unknown" vial containing the methanol sample you want to test
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Instructions

    • 1

      Start by donning eye protection, gloves and lab coat. Safety is always the first priority in the lab.

    • 2

      Make sure the GC instrument is turned on, warmed up and adjusted to the proper settings (injector temperature, column temperature, etc.). The settings you will need to use may vary depending on your device -- consult the manufacturer's instructions for details.

    • 3

      Suck up 1 microliter of the standard 1:1 mixture from the "Standard" vial by placing the tip of the syringe in the liquid and pulling up the plunger. Make sure the syringe contains 1 microliter of liquid and not air by looking through the side of the syringe and checking the level. Recap the "Standard" vial once you are done.

    • 4

      Insert the syringe through the rubber septum on your GC and push it in as far as it will go. Be careful -- the syringe tip can break if you bend it too far, and GC micro syringes are not cheap.

    • 5

      Depress the plunger quickly and remove the syringe immediately while pushing the start button on your GC. You want to make sure you get the sample in all at once and at the same time that you push the start button.

    • 6

      Watch the printout on the integrating recorder on your GC. Once the recorder has printed two full peaks, you can press "stop" to end recording. The location of the stop button will depend on your device -- see the manufacturer's instructions for details.

    • 7

      Note the location of the two peaks on the graph from the integrating recorder. The x-axis on the graph is the retention time. If the same compound is injected in the same manner under the same conditions, it will exhibit the same retention time. By testing your unknown sample on the GC and comparing its graph with the standard, you can determine whether your unknown also contains diethyl ether or methanol only.

    • 8

      Rinse the micro GC syringe by dipping it in the "Rinse" vial, sucking up a few microliters of diethyl ether and expelling it back into the "Rinse" vial. Recap the "Rinse" vial and allow the micro GC syringe to dry.

    • 9

      Uncap your "Unknown" vial and suck up 1 microliter of the unknown or test solution, then recap the "Unknown" vial.

    • 10

      Inject the "Unknown" sample and push the start button in the same way you injected the "Standard" solution.

    • 11

      Continue collecting data. Wait until the time on the x-axis of the graph is a minute or so greater than the farthest point you reached for the "Standards" sample, then press stop again.

    • 12

      Compare the graph for your "Standard" solution and the graph for the unknown. If you see a peak on the "Unknown" graph corresponding to the diethyl ether peak on the "Standard", then you can conclude your methanol sample very likely contains some diethyl ether as a contaminant.


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