Buffers show this problem when diluted excessively. Every buffer have two components- acidic and basic and acidic. For example in case of PBS, these are KH2PO4 and Na2HPO4 respectively. Whenever you face pH change after dilution adjust it not with HCL or NaOH, but a weak solution of acidic or basic comonent of the respective buffer itself (say 1.0M). Adjust pH of diluted buffer while it is being swirreled on a magnetic stirrer by adding small measured amounts of the desired component after giving sometime to let the buffer pH gets stabilized. In your case reducing or increasing the pH diluted buffer will require addition of KH2PO4 or Na2HPO4, respectively. Similar will be case in case of all other buffers. You will learn with time and practice. In case of Tris.Cl buffer, the acidic and basic comoponents are HCl and Tris base respectively. All the best Dr V K Gupta [email protected]
Sent on the go with Vodafone -------- Original message -------- From [email protected] Date: 11/12/2014 10:33 PM (GMT+05:30) To [email protected] Subject Methods Digest, Vol 112, Issue 2 Send Methods mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit http://www.bio.net/biomail/listinfo/methods or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of Methods digest..." Today's Topics: 1. PBS 1x pH dependence with time (Annalisa Neri) ---------------------------------------------------------------------- Message: 1 Date: Wed, 10 Dec 2014 08:56:56 -0800 (PST) From: Annalisa Neri <[email protected]> Subject: PBS 1x pH dependence with time To: [email protected] Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 Hi guys, I've just joined this group and I would like to ask your help for a problem. I am using 10x PBS by Lonza withthis composition: 1,440 mg/L of KH2PO4, 90,000 of mg/L NaCl, 7,950 mg/L of Na2HPO4. I use it as 1x at pH 7.3, 8 and 9. My problem is that, except for the sample at pH 7.3, in the cases at pH 8 and 9 the value tends to low down. After a couple of days pH 9 solution has lowed down to pH 8.3. I changed the pH using high concentrated NaOH, as I found in literature. Do you know if I made any mistakes that can cause this effect? Or maybe I chose the wrong kind of PBS? Thanks all for your help, Annalisa ------------------------------ _______________________________________________ Methods mailing list [email protected] http://www.bio.net/biomail/listinfo/methods End of Methods Digest, Vol 112, Issue 2 ***************************************
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