Total carbohydrate content

Remco Viëtor remco at chem.gla.ac.xukx
Tue Oct 28 13:53:28 EST 1997


Ian McFarlane wrote:
> 
> I've used this assay [Dubois, phenol sulphuric acid, RV] as well. 
> I did the assay in plastic LP4 tubes (they
> are polycarbonate I think), they melt a bit but don't seem to affect the
> reaction. The most important thing we have found is to squirt the conc.
> sulphuric directly onto the sample or the colour development isn't very
> strong.

That is because the heat developed by the mixing of acid and water
drives
the reaction. You can also heat the tubes for a while in a boiling water 
bath, though normally that is not required.
I would stick to pyrex glass tubes though, and indeed be very carefull
with both the phenol solution (poisonous) and especially the sulfuric
acid. The latter can be _very_ nasty, even when dilute. I have holed 
several labcoats while washing tubes that contained sulphuric acid:
the dilute acid gets on the coat, the water evaporates => concentrated
acid => holes.
Also, a collegue of mine got acid on his shoe. He rinsed it of
immediately
and neutralised the surface, then carried on as usual. That is, until
his
foot started itching after a while: the acid had penetrated into the
shoe
and continued working its way inwards, until it reached flesh...

Regards,

Remco
-- 
_________________________________________________________________
Remco Vietor				Department of Chemistry
remco at chem.gla.ac.uk			J. Black Building
					University of Glasgow
					Glasgow G12 8QQ
					U.K.



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