how to quantify radioactivity?

[Austin P. So (Hae Jin)]

32P will come with a datasheet that tells you the activity and 
calibration date and actually will tell you how to do the conversion to 
dpm/mol.

After correcting your counts from the assay date with the calibration 
date, you derive the pmol/ml value.

Austin

tracy wrote:

> I am trying to use (32P) orthophosphate to label some E.coli cells, and then
> extract the nucleotides and run them on a thin layer chromatography plates.
> I have questions about how to quantify those radioactive spots?  All the
> papers I have seen quantify to the level of pmol/ml, how did they do that?