Sciencemadness Discussion Board

Qualitative tests for Methyl Isobutyl Ketone

ZIGZIGLAR - 17-2-2014 at 17:39

Any suggestions for tests I can run to identify the presence of MIK in an aqueos solution of ethanol?

Zyklon-A - 17-2-2014 at 19:13

Isn't Methyl Isobutyl Ketone abbreviated MIBK?

ZIGZIGLAR - 17-2-2014 at 19:17

Yes, I believe so. :) - Any suggestions for tests I can run to identify the presence of MIBK in an aqueos solution of ethanol?

UnintentionalChaos - 17-2-2014 at 19:28

Brady's reagent, but acetaldehyde content or low concentration will foil that.

ZIGZIGLAR - 17-2-2014 at 19:42

So basically, test for MIBK prior to refluxing with sodium hydroxide and, assuming there are no other impurities, it should react with the ketones and be a reliable indication.

EDIT: I really want a Raman Spectrometer >.< - what if the ethanol had been oxidised? Brady's reagent would fail.

[Edited on 18-2-2014 by ZIGZIGLAR]

Paddywhacker - 17-2-2014 at 20:28

I presume that you don't have access to GLC equipment. A simple approach would be to react with Brady's reagent and separate the products by chromatography, either thin layer or paper.

You could make up a series of standard dilutions to make it quantitative.

ZIGZIGLAR - 17-2-2014 at 20:53

You are correct. I can only dream of having that kind of equipment. I've seen pre-loved systems going for $3-4k, so maybe one day, but I can't justify it for now. And I think I'd be more tempted by a portable Raman with a good GUI and chemical database. Have you seen those things in action? Point and shoot (even while the sample remains safely enclosed in a vial) and you get an instant quantitive reading of all detected chemicals. To drool for!

As for thin layer or paper, I could justify those setups, but I've just never had the demand to do so as I can find ways around it. I pretty much just experiment with whatever I want to, which is usually dictated by the resources I have available. Chemistry for the sake of chemistry :)

thebean - 18-2-2014 at 19:42

Quote: Originally posted by UnintentionalChaos  
Brady's reagent, but acetaldehyde content or low concentration will foil that.


Isn't Brady's Reagent shock sensitive? From what I understand they sell it as a wet powder, but still not something I'd want to be using simply for detecting MIBK.

ZIGZIGLAR - 18-2-2014 at 19:45

With basic TLC, I could just run a comparison against a sample of pure MIBK and a sample of pure Ethanol, right? I mean it wouldn't be quantified, but it would be qualitative ... I don't even remember how to perform quantitative TLC.

ZIGZIGLAR - 18-2-2014 at 20:00

Quote: Originally posted by thebean  
Quote: Originally posted by UnintentionalChaos  
Brady's reagent, but acetaldehyde content or low concentration will foil that.


Isn't Brady's Reagent shock sensitive? From what I understand they sell it as a wet powder, but still not something I'd want to be using simply for detecting MIBK.


Yes it's particularly explosive in dry form. I'm still shopping around for cheap alternative methods tbh ...

Etaoin Shrdlu - 18-2-2014 at 21:02

It might form a bisulfite adduct. It's a methyl ketone but has a pretty bulky group on the other side so I don't know. Do you have a ballpark figure for how much you're expecting to be in your solution, if any? Are you trying to find out what type of denatured alcohol you have?

ZIGZIGLAR - 19-2-2014 at 01:41

I'm expecting between 1 and 4% MIBK. Not trying to determine what kind of denatured alcohol I have, but rather, trying to find whether or not I have successfully purified it.