Chemical Forums

Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: shuhuanli on January 11, 2006, 12:39:48 PM

Title: Buffer Solution preparation
Post by: shuhuanli on January 11, 2006, 12:39:48 PM

I need a 0.05M KH2PO4 (PH=3.0)Buffer Solution as part of my HPLC solvent.  Does anyone know how to make it? (KH2PO4  99.99%, H3PO4 85%)
I try to check its recipe from http://www.bi.umist.ac.uk/users/mjfrbn/buffers/makebuf.asp. However, I don't know how to set up its ionic strength.
Then, I try to check its recipe from http://www.zirchrom.com/pass.asp. However, I don't know how to set up the Desired Acid Conc.
Thanks in advance!

Title: Re:Buffer Solution preparation
Post by: Borek on January 11, 2006, 07:06:13 PM

pH is described by Henderson-Hasselbalch equation (http://www.chembuddy.com/?left=pH-calculation&right=pH-buffers-henderson-hasselbalch) - so if you know target pH first step is to calculate correct ratio of acid and conjugated base. Ionic strength of the solution is usually forced with excess neutral electrolyte - like KCl or NaCl - to calculate its concentration you have to start with ionic strength definition (http://www.chembuddy.com/?left=pH-calculation&right=ionic-strength-activity-coefficients#17.2).