Calculating free Ca2++ with EGTA buffers

kleinschmidt at kleinschmidt at
Thu Sep 10 22:49:38 EST 1992

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
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.). 
parameters are temperature, pH and ionic strength.  The program was
in structured Basic and compiled with Borland's Turbo Basic v. 1.0 or
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,
that runs reasonably fast even on machines without math coprocessor is
available.  At that time, and perhaps still now, CABUFFER probably was
of the best and most flexible programs of that sort available in the
This program has been passed around and is presently being used by a
of labs, apparently with good results.  I can make it available to
who cares for it.  Way back, I actually meant to write a paper on the
of Ca-buffers in physiology and on the traps one can fall into doing
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
up and use Ca-buffers.  Unfortunately, all the equations are missing
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
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
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
this program may get you somewhere, certainly in simple EGTA buffers.
Jochen Kleinschmidt
NYU Medical Center
kleinschmidt at

More information about the Bio-soft mailing list