SFC Europe 2025: An Interview with John Reilly, Maria Kristina Parr, and Larry Miller

How does modern supercritical fluid chromatography (SFC) differ from traditional SFC when instruments were launched? Have issues associated with robustness been resolved? Have there been any other significant advances worth mentioning? Have there been any advances in the understanding of the fundamentals of SFC, such as retention, selectivity, and brand broadening in SFC conditions?

John Reilly: I remember when, in the mid-1990s, Eli Lilly's Separations group, led by Joe Kennedy, evaluated SFC and found it lacking in robustness for routine analytical use. However, by 2003, with the availability of Berger analytical and prep instruments, Craig White's UK team at Eli Lilly took the risk and invested heavily in SFC instrumentation and CO₂ delivery infrastructure for early-phase drug discovery. This led to SFC becoming the routine process for all chiral purifications at the UK site, eventually supporting large-scale chiral purifications for global teams. This could only have been delivered by management taking the risk in investment for bulk tank delivery, where the CO₂ is compressed to liquid and delivered to the laboratory by means of a booster pump. We must thank these pioneers of the early 21^st century, as SFC has now been widely implemented in Big Pharma drug discovery for not only chiral but also achiral purifications. This is due not only to the robustness of the instrumentation but also to the robustness of the delivery of CO₂ to the laboratory.

Maria Kristen Parr: In terms of modern analytical SFC instrumentation, the robustness of separations is drastically improved. With the current generation of technical realization, it may be considered as robust as other chromatographic separations. This seems to be mainly related to the innovations in backpressure regulation within tight limits.

Larry Miller: When you compare modern SFC instruments to those from the early 2000s, the main breakthrough was reduced detector noise and increased sensitivity. This advance now allows SFC to be used in regulated environments in pharmaceuticals and other industries. Another advance over the last 20 years is the expansion of SFC beyond low- or medium-polarity compounds and beyond research laboratories in the pharmaceutical industry.

JR: I think there have been many innovations in column technology for SFC to cover the expanding range of polarities of small molecules, particularly for achiral applications. However, I think there is still more scope to deliver more “bespoke” columns for larger molecules such as degraders, peptides, and radioligand therapies (RLTs) to cover more complex separation challenges.

MKP: Another important change in modern SFC understanding refers to its use with modifier amounts up to 60% or even more. This makes the technique more versatile and no longer considered a separate technique clearly different from high performance liquid chromatography (HPLC). Unfortunately, there is still a lack of extended pressure ranges in commercial SFC instrumentation. Pressure ranges up to 1200 bars are used in in-house-built solutions, for example, at Boehringer, but the scientific community has been hoping for a new generation of instruments for quite some time.

The conditions now employed in SFC are broader than the “supercritical fluid domain” would allow. How does that expand the application domain? How do you see SFC evolving in the future? Are there any technological developments that would make the technique more widely available?

JR: Operating instruments below the critical point introduces new modifiers for studying complex mixtures. Recent improvements include adding small amounts of water to enhance sample solubility and mobile phase polarity. Peptide, oligonucleotide, and nucleoside/nucleotide separations are being validated for both analytical and preparative use. Balancing the time spent on SFC method development within industrial laboratories may be better served by seeking further academic collaborations in this field. Although challenging, it is an opportunity to utilize SFC further for more complex new modality separations.

MKP: In that regard, SFC for chiral separation of synthetic oligos seems to be an obvious field to explore further. This field seems to combine the advances seen in SFC for chiral separation with the newly extended range of analytes. Furthermore, SFC was possible even for the analysis of highly polar analytes, ions, and even inorganic salts in recent years. With the extended range of recent SFC methods, a broad range of analyte polarities can be covered in a single analytical run. This may also help to overcome limitations of HPLC-based methods for metabolomics or biological applications.

LM: The vast majority of the SFC work performed operates outside of supercritical conditions, employing high modifier percentages (up to 80%), which allows compounds of higher polarity, such as those mentioned by John, to be analyzed or purified using SFC. While SFC uses less organic solvent and generates reduced waste compared to HPLC using the same columns, one major limitation of current state-of-the-art SFC equipment is the larger extracolumn volumes compared to ultrahigh-pressure liquid chromatography (UHPLC), which limits SFC to 3.5 mm internal diameter (i.d.) columns or larger. With UHPLC routinely using 2-mm i.d. columns, this limitation greatly eliminates the reduced solvent advantage of SFC. The last major advance in SFC equipment was almost 10 years ago with the introduction of high-performance SFC equipment by Agilent and Waters. The development of analytical SFC equipment that can routinely use 2 mm i.d. columns would expand the use of SFC.

Biographies
John Reillyis an associate director in the Department of Global Discovery Chemistry at Novartis Institute of Biomedical Sciences, and is based in Basel, Switzerland. He currently leads the separations team, where there is a focus on providing purification and analytical characterization methodologies supporting a chemistry unit with over 250 chemists. An advocate of knowledge exchange, Reilly has had global roles in discovery and development during his time at Novartis and previously with Eli Lilly. He completed his MSc. At Birkbeck College in 1992 and his PhD in analytical science at Imperial College in 2002 after his initial BSc in chemistry at Reading University, Reading, UK in 1989. His research goals include the promotion of SFC’s new chromatographic characterization and purification methods and physicochemical affinity screens to investigate drug-like properties of molecules. Reilly has published more than 50 articles and has been a board member of The Chromatography Society. He has also been on the editorial board of Chromatography Today and American Journal of Modern Chromatography.

Maria Kristina Parr has worked as a professor for pharmaceutical analysis at Freie Universität Berlin, Germany, since 2012. The research focus of her group is mass spectrometric analysis hyphenated to different chromatographic separation techniques (GC–, LC–, and SFC-MS[/MS]), with a main focus on drug, supplement, and bioanalysis as well as anti-doping research. Investigations in drug metabolism, determination of endogenous and xenobiotic compounds, and drug-drug interactions play an important role in her research. Research activities in her team consider green and white analytical chemistry principles, quality management, and analytical quality-by-design.
Larry Miller is an Associate Director in the Discovery Analytical group at Novartis in Cambridge, MA. He has spent his career performing small molecule achiral and chiral purifications at the microgram to multi-kg scale. At Novartis, Larry manages a group responsible for analytical and purification support to the Global Discovery Chemistry function. Previously, he spent 20 years at Searle/Pharmacia, and 20 years at Amgen. Larry has over 50 peer-reviewed publications and over 55 presentations at scientific meetings and he has served as co-instructor for SFC short courses in the US, Europe, and Asia. He has been involved with the Green Chemistry Group since its inception in 2007 and currently serves as President of the group. He earned his master’s in chemistry from Roosevelt University and his bachelor’s in chemistry from the University of Illinois at Urbana-Champaign, USA.