Wikipedia claims Hasselbach is a misspelling:
http://en.wikipedia.org/wiki/Henderson-Hasselbalch_equation
Since Wikipedia has now replaced the social consensus as the final
arbiter of truth ...
On Aug 7, 2008, at 3:22 PM, Juergen Bosch wrote:
> Just on a side note, can someone clarify why Hasselbach is not
> Hasselbalch or vice versa ? Or is that the same guy just somewhere
> sometime misspelled and for ever in the records ?
>
> See here:
> http://www.britannica.com/EBchecked/topic/261188/Henderson-Hasselbach-equation
>
> Jürgen
>
>
> On 7 Aug 2008, at 15:12, [log in to unmask] wrote:
>
>> Good points!
>>
>> Not only citrate is inappropriate for buffers in the pH 6.5-7.5
>> range,
>> but also (as pointed out by your colleagues at UCSC, but probabbly
>> elsewhere,
>> polyprotic acids are hard to handle, as their pKa change in a
>> significant
>> fashion depending on their concentration.
>>
>> In this case, the Henderson-Hasselbalch equation must be written in
>> terms
>> of activities rather than concentrations, otherwise it is totally
>> useless.
>>
>> Nadir Mrabet
>>
>>
>>
>> Selon "William G. Scott" <[log in to unmask]>:
>>
>>> There are 3 pKa's for citric acid:
>>>
>>> 3.15, 4.77, and 5.19
>>>
>>> so it is going to be a lousy buffer at pH 6.7 to 7.25. Also, you
>>> need
>>> to know what concentration your buffer is, and whether that
>>> concentration is with respect to the citrate ion or what. It
>>> won't be
>>> tribasic with respect to ammonium ion near neutral pH.
>>>
>>> So if for example you need 1M of this buffer, the simplest thing
>>> to do
>>> is make up a 1M stock solution of tribasic ammonium citrate and a 1M
>>> stock solution of of citric acid and then mix the two together. You
>>> can calculate the ratio using the Henderson-Hasselbalch equation or
>>> just titrate one into the other while stirring in the presence of
>>> a pH
>>> electrode.
>>>
>>> (You'll have to use the pH electrode approach if you took
>>> introductory
>>> chemistry from anyone other than me at UCSC since my colleagues
>>> think
>>> that polyprotic acids are too stressful for our undergrads.)
>>>
>>>
>>> William G. Scott
>>>
>>> Contact info:
>>> http://chemistry.ucsc.edu/~wgscott/
>>>
>>>
>>> On Aug 7, 2008, at 12:42 PM, E rajakumar wrote:
>>>
>>>> Dear All
>>>> Sorry for non crystallographic query.
>>>> Can any body mail me how to prepare Ammonium citrate
>>>> tribasic (citric acid triammonium salt) buffer pH 6.7
>>>> to 7.25 and also what is the pKa value.
>>>> Thanking you in advance
>>>> Rajakumara
>>>>
>>>>
>>>>
>>>> E. Rajakumara
>>>> Postdoctoral Fellow
>>>> Strcutural Biology Program
>>>> Memorial Sloan-Kettering Cancer Center
>>>> New York-10021
>>>> NY
>>>> 001 212 639 7986 (Lab)
>>>> 001 917 674 6266 (Mobile)
>>>>
>>>>
>>>>
>>>> Get your new Email address!
>>>> Grab the Email name you've always wanted before someone else
>>>> does!
>>>> http://mail.promotions.yahoo.com/newdomains/aa/
>>>
>>
>>
>> Pr. Nadir T. Mrabet
>> Cellular & Molecular Biochemistry
>> INSERM U-724
>> UHP - Nancy 1, School of Medicine
>> 54505 Vandoeuvre-les-Nancy Cedex
>> France
>> Tel : +33 (0)3.83.68.32.73
>> Fax : +33 (0)3.83.68.32.79
>> E-mail : [log in to unmask]
>
> -
> Jürgen Bosch
> University of Washington
> Dept. of Biochemistry, K-426
> 1705 NE Pacific Street
> Seattle, WA 98195
> Box 357742
> Phone: +1-206-616-4510
> FAX: +1-206-685-7002
> Web: http://faculty.washington.edu/jbosch
|