Fluorescein storage? - (Aug/11/2010 )

Hello,

I am using an old iCycler iQ from Bio-Rad which requires the collection of either internal or external well factors in every run. SYBR Green Mastermixes designed for the machine use fluorescein for this well factors. I am making my own "homewbrew" mastermix based on a published protocol. I ordered some fluorescein (170-8780) from Bio-Rad about 9 months ago. It arrived in an opaque tube at room temp and neither the tube or packaging said anything about storage. I naively assumed that it would be fine to store it and the dilutions I made of it at room temp. I stopped using it for about 8 months, and am now about to use it again--but realized that I better check if it is still good. According to the tech representative at Bio-Rad, as long as it collected the well factors at the beginning of the run it should be fine--although he said the dye should be stored at -20. I have limited trust for Bio Rad tech support as they have steered me seriously wrong in the past. I haven't been able to find much else online about the stability and storage conditions of fluorescein, although one clinical website (I guess it is used as a medical dye) said it should NOT be frozen.

I ran a few samples with fluorescein at the appropriate concentration in ddH20. The machine seemed to collect the well factors ok--but then when I tried putting in just ddH20, it also didn't give me any errors.

I realize I should probably just order another batch of fluorescein to be safe, but I would like to get started on the work I have to do, and am hoping I don't have to wait around for the order. Can anyone provide any information on storage of fluorescein and/or how to be sure the iCycler is collecting good well factors?

Thanks,
Dan

Hi Dan,
I work a lot with fluorescein. As a solid you may store it at room temperature for years. When it is in solution it is also very stable, but I prefer storage in the fridge - it also is stable then for years, at least 2.5 years didn't matter in my case.
I never tried to freeze it.
Greetings,
Chakchel

Thank you for your reply Chakchel. I made a new working dilution of the 1mM fluorescein stock that had been at RT for months. I used it for several qPCR runs in our iCycler without any apparent problem until I had a chance to buy a new aliquot of fluorescein and use it in my mastermixes. I don't notice any differences between the old and new fluorescein. It is apparently quite robust. However, I also have a suspicion that the iCycler doesn't even need the fluorescein despite the manufacturers contention...

Chakchel on Thu Aug 12 06:18:12 2010 said:

Hi Dan,
I work a lot with fluorescein. As a solid you may store it at room temperature for years. When it is in solution it is also very stable, but I prefer storage in the fridge - it also is stable then for years, at least 2.5 years didn't matter in my case.
I never tried to freeze it.
Greetings,
Chakchel