5 replies to this topic

[ujla80]

hi all

i m making stock sheath buffer(10X) for FACS but not getting clear solution. i am adding
EDTA =1.8 gm
KCl = 1.25
LiCl3 = 2.15
KH2PO4 = 1.3
Na2HPO4 = 11.75
NaCl = 40.6
NaOH = 0.5
in 500ml DDW.
solution becomes milky after adding Na2HPO4 (which i add in the end). what could be the reason?

[pDNA]

what is your pH? Most of the time its an issue of pH ...try to lower the pH (around 2) than add the rest and readjust the pH slowly.

Could be that you added the Na2HPO4 to fast? ...try it more slowly.

Regards,
p

[ujla80]

thanks P

actually now i know where the problem was...constituents are to be added in order...i added NaOH after adding EDTA which should be added in the end...this was resulting into turbidity after adding Na2HPO4.

regards,
ujla

but still i want to know why NaOH is causing problem??

pDNA, on Jan 16 2010, 10:10 AM, said:

what is your pH? Most of the time its an issue of pH ...try to lower the pH (around 2) than add the rest and readjust the pH slowly.

Could be that you added the Na2HPO4 to fast? ...try it more slowly.

Regards,
p

[mdfenko]

it's not the naoh that is causing the problem, it is the edta. edta will not go into solution if the pH is low.

[ujla80]

hi

yes EDTA gets dissolved at ph 8 but i added naoh after adding edta (out of order) so that it gets dissolved, as a result, solution could not be prepared..it was milky.  

mdfenko, on Jan 19 2010, 07:20 PM, said:

it's not the naoh that is causing the problem, it is the edta. edta will not go into solution if the pH is low.

[mdfenko]

how old is your naoh (did you use pellets? they get coated with carbonate by absorbing co2 from the air)?

you may have introduced an insoluble carbonate into your solution.