Calculating free Ca2++ with EGTA buffers

kleinschmidt at mcclb0.med.nyu.edu kleinschmidt at mcclb0.med.nyu.edu
Thu Sep 10 22:56:01 EST 1992

Sorry about the formatting of the preceding message.  Here is the 
clean copy:
Three years ago, I wrote a program named CABUFFER that allows you to 
calculate the free concentrations of all ionic species in a mixture of 
up to four divalent ions (e.g. Mg, Ca, Sr, Ba) and up to four 
different divalent ion buffers (e.g. EGTA, EDTA, NTA, HEDTA, citrate 
etc.).  Free parameters are temperature, pH and ionic strength.  The 
program was written in structured Basic and compiled with Borland's 
Turbo Basic v. 1.0 or with Microsoft's Quickbasic v 4.0 under MS-DOS.  
It runs very fast on PC's outfitted with a math coprocessor.  A 
slightly less capable program, CABUF, that runs reasonably fast even 
on machines without math coprocessor is also available.  At that time, 
and perhaps still now, CABUFFER probably was one of the best and most 
flexible programs of that sort available in the public domain.
This program has been passed around and is presently being used by a 
number of labs, apparently with good results.  I can make it available 
to anyone who cares for it.  Way back, I actually meant to write a 
paper on the use of Ca-buffers in physiology and on the traps one can 
fall into doing that.  Alas, the manuscript was never completed but 
early drafts of various sections are on the diskette.  They may make 
tedious but instructive reading for those who care to understand what 
they are doing when they make up and use Ca-buffers.  Unfortunately, 
all the equations are missing from the electronic version; I couldn't 
get them into ASCII format.
All the files take up about 280 Kb of space, including an introductory 
readme file.  The CABUFFER exe file is about 80 Kb long.  The Basic 
source code is also provided, so that you can modify it and recompile 
it with Turbo Basic or Quickbasic.  I can send all of this out on 
diskette, or better still, see if I can put the files into a public 
directory on our VAX from which you can download them via anonymous 
ftp.  I will have to talk to our system administrator about this.
I have little time to support this program.  Also, if you use it, you 
do so at your own risk.  But I believe that its use is easy and 
self-explanatory, and I also think that it is largely bug-free.  In 
absolutely critical applications you should always rely on using 
carefully calibrated Ca-sensitive electrodes (this is a major 
undertaking!).  Short of that, this program may get you somewhere, 
certainly in simple EGTA buffers.
Jochen Kleinschmidt
NYU Medical Center
kleinschmidt at mcclb0.med.nyu.edu

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