James Steven Kenny jkenny at ice.bae.uga.edu
Sat Jan 11 21:08:23 EST 1997

I'm having problems with precipitation forming in a Tris 
Buffer with LaCl3.  The precipitate forms slowly on the gas-liquid
interface and is apparent after a period of 12-24 hours.  The 
formation of the precipitate is pH dependent.  Precipitation does 
not occur at pH below approximately 6.7.  The amount of precipitation 
increases with increasing pH.  Furthermore, the precipitation 
seems to be dependent upon the presence of atmospheric gasses.  
If argon is used to purge atmospheric gasses from the Tris Buffer 
and the solution is capped to prohibit gas transfer, precipitation 
does not occur.  Lanthanum is a common tool to study the transport 
of Ca2+.  I have read several references that use LaCl3 in Tris 
buffers at concentrations 1 to 2 orders of magnitude greater than 
the concentrations I am currently using with no mention of 
precipitation problems.  Does anyone have experience using 
LaCl3 in a Tris buffer?  Can anyone explain the precipitation 
and help me find a solution to this problem?  

Buffer Components:

	10mM	TrisHCl
	0.8mM	MgCl2
	1.0mM	CaCl2
	5.3mM	KCl
	140mM	NaCl
	0.1mM	LaCl3

	pH adjusted with NaOH to a final pH of 7.4

Thank you for any help.  

Steve Kenny
email:	jkenny at bae.uga.edu
                       J. Steven Kenny                         
               E-mail: jkenny at ice.bae.uga.edu
         WWW: http://www.bae.uga.edu/dept/grads/jkenny

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