Check Valves and Acetonitrile

For most of the past 40 or so years that pressure-driven liquid chromatography (LC) has been used, problems related to air bubbles in the pump and detector have been at the top of the list of LC-related problems. The regular use of helium sparging or vacuum degassing reduced these problems to an acceptable level in many laboratories. More recently, the introduction of in-line vacuum degassing systems has become the norm in most laboratories. My unscientific, finger-in-the-wind survey through e-mail questions, the classes I teach and Chromatography Forum ( http://www.chromforum.com/) suggests that bubble-related problems have given up their historic top position on the LC problem list. This is good news! However, something else must take its place and I believe that check-valve problems have taken that highest (or lowest, depending upon your perspective) position.