Dear Xiao-Qing,

FACS Flow is essentially a filtered, slightly buffered saline solution with sodium azide to prevent anything from growing in it.

If you are not trying to sort cells, you could use distilled water, freshly prepared and filtered, as your sheath fluid. Use of water as sheath can cause some distortion and increased CV in the light scatter signals when your sample is of high salinity (particularly FSC) on many instruments (e.g., the FACS Canto or FACS Calibur) because of larger refractive index differences between sample and pure water, but it will not affect the fluorescence signals (and has at most a mild effect on SSC signals). The cells are exposed so briefly to the hypotonic solution (water) as they pass the flow cell that they shouldn't have much time to change their properties (i.e., burst) because of that. But you could also make an appropriate salt buffer (e.g., PBS) that will be isosmotic if you want to be sure to avoid that.  I always prepare my own sheath fluid, because I don't feel like buying and storing large boxes of essentially water in my lab.  The important point is to filter it immediately before use through a 0.2 um filter.

If you need to sort, distilled water will not work because it won't hold a charge, and you definitely need a solution with some salt.  Again, you don't have to buy the FACS Flow for that.  You can make your own, and then you have perfect control of exactly what is in it.

All the best,

We also use filtered (o.2 micro) PBS as ulternative of FACS flow. and it does not affect our experiments.

Hello

Regarding the use of PBS instead of FACSflow for sorting should be free of particles above 0.22um when they reach your flow cell unless you removed the in line 0.22u filter or it's broken. Thus prefiltering the stuff is of no use. However if you suck the stuff through a filter using a vacuum you might actually de-gas the buffer to an extend and that could make a difference as the last thing you want in your system are bubbles.

Good Luck 

Hi,

the description of the recipe is within the homepage of BD (MSDS: http://regdocs.bd.com/regdocs/view/msds/342003_53DA6371878DE5EFE10000000A1B1075_sds_pdf).

Page 6 describes...

TSCA (Toxic Substances Control Act):

7647-14-5 sodium chloride

7447-40-7 potassium chloride

7778-77-0 potassium phosphate, monobasic

7558-79-4 disodium hydrogenorthophosphate

122-99-6 2-Phenoxyethanol

7681-49-4 sodium fluoride

7732-18-5 water

Cheers

PS: good point from Saleh... bubbles are the worst enemy of the flow!

Hi,

You can use diH2O in flow cytometers without the fluidics supply system, only. The level control unit in sheath tank depends on conductivity, therefore some salts are needed. Even when you use diH2O add some preservatives/surfactants as sooner or later something will settle down and grow in lines. Problems with differences in refractive index mentioned by Peter Von Dassow are worth to consider but it also depends on your application. I have a good experience using diH2O for running cell cycle samples stained with propidium iodide and samples diluted with diH2O few minutes prior the acquisition as it actually increases PI fluorescence and improves CVs. Of course it works for properly ethanol-fixed cells, only. 

Regular FACSFlow is ( from the MDS ):

sodium phosphate, dibasic