Identification of purity of the protein - (Feb/23/2011 )

I have purified a protein and it appears a single band on a SDS-PAGE gel when stained with Coomassie blue. I need to know the purity of the protein. Often in many publications, I see many researchers mentioning similar to this "purity of the protein was >95% homogeneous as assessed from the SDS-PAGE gel". I know a software AlphaImager 2200, which density scan a lane and give the percent amount of all the proteins in a lane. But that was in previous lab, currently I am looking for a similar software available online for free. Or any other methods to identify the purity of the protein is also welcome.

thanks in advance
-rbrgouda

Trial version of commercial software - like ImageQuant or GelScan.
Or free software - like ImageJ.

ImageJ does everything what you need. It is free and you can find many information on how to use it on the net.