Analysis of schiff base

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PRAVEEN PALIWAL
PRAVEEN PALIWAL's picture
Analysis of schiff base

Sir,

we are analyzing the following analyte which is schiff base. Right now we are analyzing it on GC [ Column - Supelco -TM SPB-5 , 15 meters , 0.53mm ID and 5µm film thickness. But after 10-12 injection some hums are observing and these are not going even after conditioning the system and column. Finally we cut the both end of column about 3-4 inch and then inject the hums was not observed. But the problem is temporerily solved again 10-12 injection hums are again observed.
Sir we want to analyze this analyte on HPLC ,but in water this analyte get hydrolyzed and gives it's precursor Isobutyrophenone. How can we get the stable form of this compound so that we can get HPLC anlysis.
I also used Sodium borohydride for this but solution was not found please suggest us what we have to do?

Regards

praveen

Dr. Analytical
Dr. Analytical's picture
You should be able to

You should be able to dissolve this compound in a dry organic solvent such as acetonitrile or methanol, and then inject into a reversed phase system.  If you use a fast column, maybe the compound will not degrade before it elutes.

The other option is the accept that this compound hydrolyzes in water, and analyze the decomposition product.  If you dissolved samples and standards in the same solution, you can still analyze the schiff base, but it would be present as the decomposition product.   Of course, this would not work if you have residual amounts of the isobutyrophenone in your original sample.

What is the purpose of this analysis?  If we have more details maybe we can suggest something different.

PRAVEEN PALIWAL
PRAVEEN PALIWAL's picture
Sir,

Sir,

Bacially this schiff base is made form isobutyrophenone. and our task is to get separation between these two. In water or aqueous media it will get hydrolyze and convert it into isobutyrophenone.
Should we try Normal phase analysis ?

Dr. Analytical
Dr. Analytical's picture
You can try normal phase but

You can try normal phase but I do not if you will get much retention.  The original phenone will elute first, and the schiff base should elute later.  Solubility may also be a problem  I would try a silica column with methylene chloride.  If you get no retention, then you will have to start with a hexane-based mobile phase.  If you have too much retention, then you may have to add in a more polar solvent such as acetonitrile.

How fast does this compound hydrolyze in water?  Is it immediate, or does it require a few minutes?

PRAVEEN PALIWAL
PRAVEEN PALIWAL's picture
It is immidiate hydrolyze in

It is immidiate hydrolyze in water and convert's into it's precursor isobutyrophenone.
I can't use acid also like TFA or acetic acid because in acidic media it will again hydrolyze.
I want to analyze it on Methanol and methylene chloride.

Dr. Analytical
Dr. Analytical's picture
OK, then you will have to try

OK, then you will have to try normal phase separations.  You must dry your solvents carefully, as methanol is very miscible with water, and even methylene chloride can have some water dissolved in it. 

chemistorg
chemistorg's picture
Schiff Bases cannot be

Schiff Bases cannot be analyzed via GC because they breakdown to their original components. You need a non destructive method  like HPLC in a polar or polar aprotic solvent to get the true analysis.

Sami Tuomivaara
Sami Tuomivaara's picture
Just a quick comment,

Just a quick comment,

Dr. Analytical pointed out quite a few problems with analyzing the native compound. Reduction (with sodium cyanoborohydride, NaBH3CN) might be the least painful way to go. It can save a lot of troubleshooting time.

Cheers,