High performance liquid chromatography (HPLC) and ultrahigh-pressure liquid chromatography (UHPLC) stationary-phase technology
have arrived at a crossroads, with several competing approaches vying to become the standard column type for use in future
routine separations. To understand the path forward of sub-2-μm porous particles, superficially porous (core–shell) particles,
silica monoliths, and polymeric monoliths, a survey of 14 leading HPLC–UHPLC column experts was conducted in June 2013. A
series of questions was directed to the experts, and this report serves as a summary of their inputs on recent column advances,
deficiencies and problems, instrument capabilities, and future directions of the technologies.
More than 25 years ago (1), when high performance liquid chromatography (HPLC) was in its teenage years and many chromatographers
were unsure of which way column technology was going to go, I conducted a survey of leading experts at the time in column
technology. The survey was entitled "The Future of HPLC Column Technology: A Survey of Experts" and predictions were made.
Then, 20 years later in 2007 (2), I revisited these predictions, discussing where the experts were "right on" and where they
missed the boat. Rather than repeating those earlier observations and comparisons, the reader is referred to those original
Today, I believe that liquid chromatography (LC) column technology, particularly in stationary-phase formats, is at another
crossroads. Since the original survey (1), porous particles have become much smaller; now sub-2-μm porous particles are available
from more than 30 companies. As a result of these smaller particles, column pressure drop has become a bigger issue. Ultrahigh-pressure
liquid chromatography (UHPLC) has now become a household word with instruments capable of pressures of nearly 20,000 psi.
Superficially porous (core–shell) particles (SPPs), previously referred to as pellicular packings, mostly larger in diameter than the sub-2-μm particles, have come into their own as lower-pressure-drop replacements for
the smaller sub-2-μm columns but with similar efficiencies. Silica monoliths are now into their second generation and show
better efficiency, but at the expense of greater pressure than the first-generation monoliths. Polymeric monoliths are starting
to show some promise for both large and small molecule separations and offer greater chemical stability than silica-based
At the HPLC 2013 conference in June, I connected with a selection of today's experts, and most agreed to respond to a questionnaire
on the subject of HPLC column technology. This time I decided not to include experts from companies specializing in column
development because their answers were somewhat biased in the first survey and some were reluctant to express their predictions
on future column developments as that might divulge proprietary product development information. This installment of "Column
Watch" is a summary of the responses to those questions and presents not only a current status report on LC stationary phases,
but also a look into the future. In this survey, the "column" refers to the stationary phase inside the hardware and not necessarily
to the hardware itself.