Degassing Mobile Phase Solvents
As we have seen thus far, appropriate degassing of mobile phases is an effective means of inhibiting the various problems caused by dissolved air in mobile phases, such as problems with formation of bubbles in flow lines or the detrimental effects on detection caused by changes in the level of dissolved air (or oxygen).
Until recently it was commonly thought that degassing with an aspirator, as illustrated in the introductory remarks, should always be performed, but as indicated in this article, there are many considerations to be noted. Consequently, currently vacuum degassing using a gas-liquid separation membrane has become very popular, whereas helium purging is used for stricter degassing applications.
Under some specific analytical conditions, degassing the mobile phase can even cause the appearance of peaks from dissolved air in sample solvents.
I hope this article will be helpful for all HPLC users in selecting and using a degassing method appropriate for their application.