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Does Trypan Blue expire? - (Apr/29/2008 )

I ask because my lab has a sealed bottle of Trypan Blue dye sitting on a shelf that is past its expiration date. Since we've not opened it yet, I'm loathe to throw it out. All we use it for is counting cells in a hemocytometer for passaging and testing.


Yes, it does expire. If it has crystals floating around in it (use a microscope) it has expired. You can still use it by the crystals make counting quite hard. I guess you could filter it and use it if it has crystallized out.


No sign of crystals - so still good?


Besides the crystals (which can be filtered out), the only other thing to watch for is bacterial/fungal growth. Otherwise, I have never witnessed a bottle of Trypan Blue expire/go off, and that's with nearly 20 years cell culturing.

PS: What on earth do bugs find in Trypan Blue to eat?