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Techniques & Tools Liquid Chromatography

The Analytical Triumvirate

The development of analytical techniques is dependent on the interest and investment of three possible contributors: i) manufacturers who build innovative systems and promote them; ii) academic researchers who stimulate innovation, improve understanding of the fundamentals, demonstrate feasibility of applications and educate future users; and iii) industry users who demand technology improvements in setting high requirements on system quality, reliability, robustness and cost-effectiveness.

When one of these three elements of the triumvirate is missing, analytical methods do not progress well. For an example of such impaired development we need only look at the history of supercritical fluid chromatography (SFC).

First described in 1962, SFC initially attracted the attention of academics for allowing the elution of thermolabile analytes with the help of a denser fluid than the hot gases employed in gaseous phase chromatography. Note that HPLC did not exist at the time. Carbon dioxide became a favorite eluent, because the supercritical conditions could be reached at low pressure and temperature values, and because of the added benefits of a cheap, abundant, non-toxic, non-flammable, non-corrosive solvent. However, the limited elution strength of neat CO2 prompted the use of co-solvents in the 1980s (most often an alcohol, such as methanol).

Technical development demanded real innovation – pumping a compressible fluid and mixing it with a liquid co-solvent in well-controlled proportions; injecting liquid samples into this compressible mixture; controlling back-pressure to obtain the desired fluid density – after all, such requirements surpassed those of typical GC systems and then-developing HPLC systems. No surprise then that only a few manufacturers settled on designing dedicated SFC systems – most users employed homemade systems.

In the 1990s, although much research showed the potential of SFC in many application areas, SFC never really saw the light of day. The limited involvement of manufacturers in the SFC space was compounded by HPLC coming of age, deterring industry users from investing time and money in SFC.

In 2000, SFC had essentially survived as a preparative-scale technique for the resolution of enantiomers, where the economic advantages of CO2 were widely recognized. At this point, academics had essentially abandoned the technique, which was when I, as a new chromatographer, entered the field and learnt about SFC (and other types of chromatography) with someone who had practiced the technique for over 10 years. When attending chromatography conferences during this period, we were rather lonely. There was barely a talk to go to and only a couple of posters mentioning SFC – usually the ones we had brought ourselves. You could count on the fingers of one hand the academic teams still putting effort into SFC. However, in user meetings, where only industry users attended, we could feel a strong demand for fundamental work to help improve their understanding, as well as improved systems to perform more reliable and effective analyses.

It took the efforts of two major manufacturers, who finally introduced analytical systems that met the high-level requirements of the industry at the beginning of 2010, to reawaken the attention of academics. Today, chiral separations are still of interest, but achiral applications have particularly increased. The publication rate of SFC papers is higher than ever – about twice the number produced ten years before. A close examination of the contributors to SFC literature shows that industry contributions have not varied much in the past 20 years, possibly indicating that the level of interest has remained constant. It is only the contributions of academic researchers that have  drastically reduced – but that number is now increasing again.

As an academic researcher, I feel really concerned by my observations, which make me wonder about the responsibility of academics in the development of a particular technique – not just in terms of fundamental understanding, but also in education. Even though I have worked on SFC for over a decade, I have only recently introduced SFC lectures to my students. I guess I also felt that it was not worth spending time on a technique that they were so unlikely to need in their future careers... Most importantly, I am concerned about our role as stimulators of innovation. Though I am happy about the current interest in a technique I have supported for several years, I wonder about our tendency to follow trends (possibly because it is easier to publish on a trendy topic) when we should, on the contrary, inspire new directions. In other words, academic researchers should be thought-leaders, not followers.

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About the Author

Caroline West

Caroline West, now an associate professor in analytical chemistry, ICOA, University of Orléans, France, only heard derisive comments when she first start working with supercritical fluid chromatography: “Why the hell are you wasting your time with this non-existent technique?” Now, the tide has turned. West discovered SFC when she was only a “baby” analytical chemist, so she can no longer live without it. “Unravelling its surprising phenomena and projecting the quasi-unlimited possibilities of this separation method is keeping my neurons 150% busy. I’ve no time to fall into the boredom of using long and fastidious methods with unsatisfactory resolution.”

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