Question about pH of PBS - (Jan/24/2008 )

Hello,

When preparing PBS buffer, the pH should be 7.2, and should NOT involve adjusting with acid or base. I was wondering why is this? Just a little curious.

Thanks for you help.

-Astudent-

QUOTE (Astudent @ Jan 24 2008, 05:25 PM)

Hello,

When preparing PBS buffer, the pH should be 7.2, and should NOT involve adjusting with acid or base. I was wondering why is this? What's in PBS when making it causes the pH to be 7.2? Just a little curious.

Thanks for you help.

PBS is phosphate buffered saline

From wikipedia:

It is a salty solution containing sodium chloride, sodium phosphate, and (in some formulations) potassium chloride and potassium phosphate. The buffer helps to maintain a constant pH. The concentration usually matches the human body (isotonic).

-thewhorule2002-

QUOTE (Astudent @ Jan 24 2008, 10:23 AM)

Hello,

When preparing PBS buffer, the pH should be 7.2, and should NOT

involve adjusting with acid or base. I was wondering why is this? Just a little curious.

Thanks for you help.

there are several composition of PBS around; you may titrate the pH you like utilizing NaH2PO4 and Na2HPO4

-The Bearer-

I adjust PBS to pH 7.5 . Some preparations of PBS is just that it ends up somewhere between 7.1 - 7.5 . One can adjust to one's preference.

-scolix-

Phosphate Buffered Saline is, remarkably, buffered with phosphate. The ratio of the different phosphates added sets the pH.

-phage434-

QUOTE (The Bearer @ Jan 24 2008, 12:37 PM)

QUOTE (Astudent @ Jan 24 2008, 10:23 AM)

Hello,

When preparing PBS buffer, the pH should be 7.2, and should NOT

involve adjusting with acid or base. I was wondering why is this? Just a little curious.

Thanks for you help.

there are several composition of PBS around; you may titrate the pH you like utilizing NaH2PO4 and Na2HPO4

Thanks for the reply, but my question was more about WHY the pH is 7.2 without adjusting. I don't really understand how phosphates work in the solution...

-Astudent-

few topics on the forum dealed with preparing phosphate bufer.
I put you a link for ex
http://www.protocol-online.org/forums/inde...?showtopic=9323

principle is that you have acid and it's conjugate base in solution : and HPO4 and H2PO4. These make the equilkibrium to reach the 7.2 ph.
So it's not truly right that you don't adjust the pH with acid and base.
It means, you don't need to adjust with the classical HCl, KOH or NaOH to reach the desired pH. You only ajust with one of the acid/base couple partners.

-fred_33-