Webster's New Collegiate Dictionary defines a myth as "an ill-founded belief held uncritically, especially by an interested group." Could that group be misinformed
chromatographers? In the first of a two-part feature from Ron Majors, the top 10 high performance liquid chromatography (HPLC)
column myths are presented and attempts are made to demystify them by offering some evidence that they are untrue. This part
will feature myths 10 to six.
In any field there are often "misconceptions" or "myths" that are perpetuated and passed on to the next generation. These
myths are often driven by a lack of understanding by practitioners of the real issues. And these myths can change as time
moves on. Originally, seven years ago, in a "Column Watch" installment (1), the 10 most popular myths of the time around high
performance liquid chromatography (HPLC) column technology were demystified by discussing the issues at hand. Because HPLC
is approaching its 50th year, many column myths have already been passed down to two generations of liquid chromatographers.
Recently, ultrahigh-pressure liquid chromatography (UHPLC) has come into its own and a new set of myths are arising. The purpose
of this installment of "Column Watch" is to revisit and update readers on the most popular column myths of today and try to
dispel some of these myths before they get perpetuated. This column is an adaptation of an oral presentation at HPLC 2013
in Amsterdam, The Netherlands (2). In keeping with the "countdown theme," I will start with number 10 and work my way to the
Myth 10: Air Will Kill an HPLC Column
HPLC and UHPLC columns are shipped with plugs of either stainless steel or polymeric construction installed at both end.
Users are told that a column should always be capped tightly after the column is disconnected from the instrument. The thought
is that large amounts of air can get inside the column, perhaps damaging the packing material, causing bubbles in the detector
flow cell when installed into the HPLC system in the future, and maybe disrupting the packed-bed morphology. First, one should
realize that the tiny hole in the endfitting is less than 0.02 in. in diameter and thus has an extremely small cross-sectional
area. If left open the small amount of air that diffuses into the column could hardly cause irreparable damage. Depending
on the volatility of the solvent used to store the column, there could be some evaporation near the end of the column. But
large quantities of air would have a hard time diffusing through the microparticles in the packed bed seeing that we need
thousands of pounds per square inch of pressure to push liquid mobile phases through these micrometer-sized particles. The
small amount of air that could conceivably enter into the ends of the column would be immediately dissolved once the system
was pressurized or, at least be flushed out in the initial pressurization in a short time and should not cause any problems
with the chromatography later on. However, if you would feel more secure by capping the endfittings by all means do so.