Sodium Orthovanadate Preparation

Dr Engelbert Buxbaum via methods%40net.bio.net (by engelbert_buxbaum from hotmail.com)
Mon Apr 20 11:18:22 EST 2009


Am 18.04.2009, 15:57 Uhr, schrieb Lionel Brooks 3rd  
<Lionel.Brooks from dartmouth.edu>:


> Sodium orthovanadate preparation:
> This needs to be done under the fume hood
> • Prepare a 100 mM solution in double distilled water
> • Set pH to 9.0 with HCl
> • Boil until colorless
> • Cool to room temperature
> • Set pH to 9.0 again
> • Boil again until colorless
> • Repeat this cycle until the solution remains at pH 9.0 after boiling  
> and cooling
> • Bring up to the initial volume with water
> • Store in aliquots at -20 ̊C
>
> Much to my chagrin the solution is not colorless after more than 30 min  
> of boiling. Any ideas on what I am doing wrong?

There seems to be an impurity. Adding a spatula of activated charcoal  
before the first boiling and filtering afterwards might help. There may  
also be a trace of phosphate present, wich gives a yellow tint (or  
precipitate, if the concentration is high enough). Make sure that you have  
pure reagents and that the glassware is free of phosphate (detergent!)


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