What is the secret ?

laurent fleury lfleury at free.fr
Sat Feb 5 14:33:13 EST 2000


I am trying to manufacture those medias :

(i) Tryptone Salt, according to AFNOR, is composed of
- Trypsic Caseine Peptone : 1,0 g/l
- Sodium Chloride : 8,5 g/l (and not 4,3 g/l as my last mail)
+ pH = 7,0 +/- 0,2

(ii) Tryptone Salt + Neutralizing, according to Pharmacope, is composed of
- Tryptone Salt (composition and performance issues are given above (i))
- Polysorbate 80 : 30,0 g/l
- Lecithine (Yolk) : 3,0 g/l
- L Histidine Chlorydrate : 1,0 g/l
- Monopotassium Phosphate : 3,6 g/l
- Disodium Phosphate (2H2O) : 7,2 g/l
- Sodium Thiosulfate : 5,0 g/l

I have difficulties to keep the Ph level steady. I lost 0.2 to 0.3 Ph after
1 month. I know that I need to compensates the evolution by an unknown
additive not mentionned on the technical label. Unfortunately, I do not know
any thing about it.

Could you tell how I coukd have a constant level of Ph in those medias.







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