ptlmayank - 9-11-2011 at 22:54
i have read that methanol having moisture and dissolve oxygen so kindly suggest the best method to purified methanol. thanks in advance.
woelen - 9-11-2011 at 23:59
Add anhydrous sodium sulfate or magnesium sulfate to it, let it stand for a while and then distill until just a few percent of the original liquid
remains. The methanol obtained in this way will be much more dry.
If you want it really dry, then I think you have to resort to more advanced methods and you may need molecular sieves (3A), but I'm not sure about
whether methanol is absorbed as well. Use of P4O10 is not recommended, that may form phosphate esters with the alcohols.
The distillation process also removes most of the dissolved gases. These simply will be expelled from the hot liquid. Of course you always will have a
trace of oxygen in the methanol because it is in contact with air
bahamuth - 10-11-2011 at 10:56
HPLC grade is such a wide term if you ask me.
If you need methanol with ultra low absorption in the low UV range you need to distill it several times with various drying agents and only take the
"best" fractions.
For regular HPLC, drying it properly and distilling it keeping the "best" fraction will go a long way.
One problem with such procedures is the "batch" factor, that is every batch will have slightly different compositions, potentially giving variations
in your experiment between batches. Therefore, if you want to do a large series of samples, clean up a large batch of the methanol. Large distilling
equipment is relative expensive so you might just buy the HPLC grade methanol as it isn't really that expensive compared to e.g. analytical grade.
Dissolved gases are usually removed in the HPLC if you have a degasser unit in there, or you might just have to put it in a ultrasonic bath before
use.