pH change after ATP addition - (Oct/29/2011 )

I am dissolving the ATP (200 mM and I need more to dissolve) Phosphate buffer (K2HPO4, KH2PO4) pH of 8.0, and dissolving the pH comes to 4.0 almost. How to bring the pH back to 8.0. should I used one of these salt to adjust the pH or NaOH. or some thing else should be done. I have no idea about it.
Any suggstion????

regards

Sorry, I'm not quite certain what you are doing here. Is this correct: you are dissolving ATP in phosphate buffer that you have already made up?
If you are dissolving all three together at the same time, you should probably try dissolving the ATP in the buffer after you have made it.

If you are dissolving the ATP in pre-made buffer, then you could try adding more phosphates, but you would alter the concentration of the salts which would alter the osmolarity. I think you would be better off pHing with NaOH.

Yes I am dissolving the ATP in already made phosphate buffer of pH 8.0, 50 mM, but If I dissolve the ATP pH goes to 4.0. Some body advice me to make buffer of higher concentration like 200 mM with pH 8 and then dissolve the ATP and check the pH how much it drops.

regards

do you need the final concentration of the phosphate buffer to be 50mM? if so then add a concentrated stock, adjust the pH and adjust to final volume.

you can also pre-adjust the atp then add the concentrated stock phosphate buffer and bring to final volume.