When using perchloric acid in the mobile phase;

0.3% in aqueous (pH = approx. 1.3)

85/15 aqueous/acetonitrile

Can silica based columns handle this mobile phase?

Please give your experiences with using perchloric acid. Thank you.

Hi,

We routinely one one method with a perchloric acid buffered mobile phase, and have experienced decent column life >500 injections.

This definately wouldn't be my first choice to start development with, but if you are inheriting it, it will probably work.

The problem with working at pH1.3 is the slow acid hydrolysis of the siloxane bond Si-O-R. You can probably extend column life by being careful to flush the buffer from the column at the end of a sequence and placing the column in a suitable storage solvent. You may also want to try one of the di-isopropyl "stable bond" C18 columns.

Good Luck.

Thank you.

I also read about di-isopropyl C18 columns in my search. I will try the SB columns.

It seems that perchloric acid can be buffered to pH>2 by addition of NaOH. Of course selectivity will be an issue as the pH is adjusted, but this may work. Can anyone think of why I should not attempt this?

How about the reactivity of perchloric acid with HPLC pump parts/ accessories? Does anyone have experience with compatability?

There is no reason why you cannot use perchloric acid or sodium perchlorate with your HPLC system.
I have used for several months 10% acetonitrile in 0.5 M sodium perchlorate (no pH adjustment, then probably pH was around 7) for a chiral separation on a Daicel RP column, and the whole system (pump, autosampler, UV and column) did not show any sign of accelerated degradation/consumption

There's a difference between pH 2 perchloric acid and what you call a "buffered" solution. In the latter case, adding NaOH serves to titrate the acid, to produce sodium perchlorate. Hence, this solution will have a higher ionic strength than a pure perchloric acid solution prepared to achieve a pH of 2. As far as the system goes, the less salt the better.