I disagree. Trypsin in solution over time will cleave (and thus inactivate) itself. Bacteria can also produce siderophores that rival EDTA in metal chelating ability. Streak your solution out on some nutrient agar or look at it under the microscope to verify contamination. Both reagents are cheap, so best to remake anytime you suspect contamination.

I suppose no.

No.They don't get contaminated at least by bacteria that is commonly used/found in the lab's. 

I disagree. Trypsin in solution over time will cleave (and thus inactivate) itself. Bacteria can also produce siderophores that rival EDTA in metal chelating ability. Streak your solution out on some nutrient agar or look at it under the microscope to verify contamination. Both reagents are cheap, so best to remake anytime you suspect contamination.

I agree with Dr. Douglas. Yes, it does. I've seen it in our lab too. Inoculate some liquid media with your Trp-EDTA and mostly you'll be able to see any contamination within 6 hours.

I agree with Dr. Douglas A Mitchell .

Absolutely. I found contamination in my aliquot of Trypsin today and it was only a fortnight old.