[aser25]

Hello

I am trying to detect some compounds with TLC. I am developing it with a mixture of chloroform:methanol:acetic acid glacial:water. And I am using 20% phosphomolybdic acid in ethanol as stain.

However, I am getting a lot of grayish spots background. Please see attached image.

Any insight what might have gone wrong?

Thank you

[rolnor]

Can you tell us about the compounds? Do you heat the plate when you stain it?

[aser25]

The compounds are phosphatidylcholines. And yes, heated the plate for 15 min @ 65 Celsius.

[hollytara]

Did you heat the plate before you stained it to dry out all the solvent?  The PMA will stain any residual acetic acid.  Your phosphatidylcholines wont evaporate so be sure all the acetic acid is gone.  I would dry in the oven for 15 minutes or more.

[aser25]

I did not, I will try that. Thank you!

[Babcock_Hall]

When I have trouble visualizing a compound, I sometimes use a broken TLC plate and just try spotting and staining, without running the plate.  This may save a little time in troubleshooting.