what is the exact composition of the Hepes Buffered saline reagent??
Please note the composition of HEPES saline,
The pH of this solution should be adjusted to 7.4 using NaOH.
Kindly follow the link also.
Importantly keep in mind phototoxicity of HEPES when exposed to ambient light due to the production of hydrogen peroxide. So its strongly advised to keep any HEPES containing solution in dark.
see theses refs :
* Toxicity of light-exposed Hepes media. Lepe-Zuniga JL, Zigler JS Jr, Gery I. Journal of Immunological Methods. 1987 Oct 23;103(1):145.
* Analysis of the cytotoxic effects of light-exposed HEPES-containing culture medium.
* Zigler JS Jr, Lepe-Zuniga JL, Vistica B, Gery I., In Vitro Cell Dev Biol. 1985 May;21(5):282-7.