Method needed for TLC

[vishnu]

Dear guys,
I got problem with the method of analysis specified in the european pharmacopoeia for metformin hydrochloride.
I am not getting any peaks after run using ninhydrin.

Is there any suitable method for metformin in TLC??? can anyone help???

[tom jupille]

Try spotting a sample on a plate and then spraying with ninhydrin *before* developing the plate. If you see no spot, then your ninhydrin reagent is bad (or your conditions are wrong).

[vishnu]

or can i try any other materials other than ninhydrin??? or is there any valid method to spot impurity F using TLC???

please help

[tom jupille]

any valid method to spot impurity F using TLC???

Since I have no idea what "impurity F" is (and presumably, neither does the EP, or they would have identified it), the answer is "No". If you use another visualization techique, you will have to validate your method.

[vishnu]

No. EP has Impurity F - N-methylmethamine. for that i need TLC method to test. Its not giving any spot using EP method. that was my problem. any solution for this???

[DSP007]

You heat plate after ningydrine?

[Equisraya]

Hi!
From Clarke's you have this tlc systems (don't know if can visualize the impurity):


Thin–layer Chromatography.System TA—Rf 01; system TB—Rf 00; system TC—Rf 00; system TE—Rf 00, 80; system TL—Rf 00; system TAD—Rf 00; system TAE—Rf 03, 93; system TAF—Rf 48. (Acidified iodoplatinate solution, positive.)


Regards!

[vishnu]

i cant understand what you said.

I tried with two visualization - one with ninhydrin and another one with the combination of sodium nitroprusside, potassium ferricyanide and sodium hydroxide as prescribed for metformin in Ph.Eur.
I got spot in metformin. but i am not getting any peapks in ref solution that was DMA HCL. without getting spot in DMA HCL, i cant get peak with impurity F.
So i cant approve the batch as COS Grade.
This is the problem for me. please help

[tom jupille]

The ninhydrin reaction for amines has been around for a loooong time, so you are obviously doing something wrong.

Begin by *not* running the TLC. Take a used plate and press your thumb onto the silica near one edge. Then spray the plate with your ninhydrin reagent and heat the plate. You should see a purple thumbprint. If you do not, then either your reagent is too old, or it has been incorrectly prepared, or you are not heating enough.

If you *do* see your thumbprint, spot some of your standard solution on the plate, let it dry, and do the ninhydrin procedure. If you do not get a dark purple spot, then your standard is bad (too dilute, perhaps?).

If you do see a spot, then spot another plate and run the TLC.