The annals of scientific history are full of promising technologies that, for various reasons, never gained traction. Back in the early 1960s, the development of supercritical fluid chromatography (SFC) was seen as a major leap forward in separation science, offering a significant speed advantage over other methods. However, its high-pressure operating environment proved to be too challenging for widespread adoption. Instead, the more robust high-performance liquid chromatography (HPLC) technique soon became a prevailing separation technology and SFC was relegated to niche applications.
But the SFC story didn't end there, thanks in part to the work of Eric Lesellier and Caroline West, associate professors of analytical chemistry at the University of Orsay and University of Orléans, respectively.
"The problem with SFC was that, for several years, it was completely deserted by academics," said West. "You could count on one hand the number of teams in the whole world who were still working on SFC."
One of those researchers was Eric Lesellier, who became intrigued by SFC and its potential about 25 years ago. He discovered that many of the fundamental properties of SFC analysis had never been fully explored and documented. For example, Lesellier noted that SFC columns had never been properly classified, so he began an effort to develop that classification system two decades ago.
"I'm interested in understanding and modeling the interactions which occur in supercritical fluid chromatography on packed columns, with varied stationary phase natures -- from polar silica to C18 silica, aromatic, polymeric, fluorinated phases," noted Lesellier. "We use different models or tests to achieve stationary phase classification."
When Lesellier became West's PhD advisor in 2002, she found herself gravitating toward SFC, too. Her PhD thesis was devoted to exploring the applicability of porous graphitic carbon (PGC) stationary phases in SFC.
"Maybe it’s a bit of the rebel in me, because I’m interested in the things that nobody is interested in," said West. She soon found out that SFC was far from a technology with limitations.
"There is no real application range that is specific to SFC," she asserted. "Probably everything we can do in SFC, we can do in either GC or LC. Only we do it better," she added with laughter. "My point is that, for instance, when you have an application that is done in GC, you need to derivatize, but you can do the same with SFC without derivatization. Or when you have an application that is done in LC, let’s say you do a chiral separation, you can do it in SFC, as well, only it will be faster and more cost effective. So there’s not an area that is really specific to SFC. It covers the areas of GC and LC -- only to me, it’s a better technique in many cases."
West and Lesellier have invested much of their research time to proving that point, focusing on the fundamentals of chromatographic selectivity, not only in SFC, but also HPLC, hydrophilic-interaction chromatography (HILIC), and enantioselective separations.
"All our work is devoted to a better understanding of what we’re doing and having a more clever way of developing a method," said West. "So the developments we have done in achiral SFC show that, with a clever selection of columns at the beginning, the method development is much faster."
Lesellier and West have published extensively, with more than 50 papers spanning a range of subjects. Caroline West was recently recognized for her work by LCGC magazine, which named her its 2015 Emerging Leader in Chromatography. She was also named among the "Top 40 Under 40" by The Analytical Scientist in 2014.
As partners in both science and life, West and Lesellier feed off each other's knowledge and interests.
"There are some points where we still work together, and we have some common projects," West noted. "And other points where we have separate projects. For example, Eric is working more in the field for natural products, extracting bioactive compounds, especially for the cosmetic industry."
"For my part, I’m still more interested in the fundamental aspects," she said. "For instance, trying to have a better view of the polarity of the analytes that we may be able to use, especially because we have many people asking about the possibility of analyzing biomolecules. So we really do not have an answer about that. It’s simply unexplored."
West traces her interest in analytical chemistry back to an early fascination with forensics as a student. However, her career could have taken a different turn.
"I loved science and literature, both to the same extent," said West. "So I do not have a feeling that I really chose science. It’s rather that it’s a question of opportunities, actually. I don’t know how it is in the US, but in France, when you’re good at both science and literature, I think the teachers are pushing you toward science."
While both West and Lesellier are prolific researchers, they also devote considerable time to evangelizing for SFC via training and presentations.
"We teach SFC to master classes of, like, 15 students," West said. "We also teach it to professionals -- people in industries that want to be educated in SFC -- about five to ten people per year. And then there are tutorial short courses we may do in conferences."
Caroline West credits Waters' introduction of its ACQUITY UPC2 System as another factor boosting the technology's resurgence.
"There are lots of people who are now very interested in SFC," she said. "The developments in the instruments from Waters and others are certainly helping in this direction, because they make working with SFC more similar to HPLC, so it’s a little less frightening than it used to be. Years ago, if you had a conference session on SFC, you'd have, like, 20 people in the room. And now it’s usually more than 100."
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