Many industries benefit from the green advantages of SFC; learn what industries attend Green Chemistry Group international SFC conferences.
Academic research has encouraged the revival of SFC as a routing analytical tool. The training of students in the biological, chemical, and food sciences plus chemical and biochemical engineering in academia has been most apparent in Western Europe and the United States.
Significant effort has been devoted to determining the fundamental aspects of solute-solute, solute-fluid and solute-modifier interactions in supercritical fluids and supercritical fluid processes. Many of these studies have been advanced by theoretical calculations and modeling through research in academic laboratories. The technical literature is ripe with published work from universities throughout the world.
Energy and Petrochemical
Two-dimensional gas chromatography is popular in the petrochemical sector because it improves the efficiency, selectivity, and resolution of separations for the analysis of very complex samples. But it has become desirable to develop a comprehensive 2D separation technique that allows the easy elution of low volatile compounds that are difficult to elute in GC x GC while preserving flame ionization detection.
This technique is SFC when neat carbon dioxide is used as the mobile phase.
Given that the best SFC kinetic features, which include (a) fast separations, and (b) low mobile phase viscosity that allows (c) long packed columns which exhibit (d) ca.100,000 theoretical plates that under reasonable conditions could provide (e) a peak capacity in the same range as GC x GC can be feasible with SFC x SFC. Current research in the use of SFC for energy and petrochemical related separation problems will only increase the applicability of SFC in these areas.
Environmental application of SFE has steadily gained interest in the analytical community over the past few decades due to its inherent advantages over conventional liquid extraction techniques.
Based on the solvating and mass-transfer properties of supercritical fluids and advantages over GC and LC applications, SFE techniques have been adopted for extraction of materials originating in complex matrices, including use by the US Environmental Protection Agency for certain applications.
Some of the most common pollutants extracted using this technique include Polynuclear Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs), Dioxins, Pesticides, Phenols, Surfactants and Metallic compounds.
As the technology continues to advance, the integration of online SFE/SFC, coupled with standard detection techniques such as UV and mass selective detectors, provide an avenue for standardized approaches to sample extraction and chromatographic separation and analysis techniques.
Foods are extremely complex matrices, and separation tools with high resolving power are used throughout the food industry. Scientists working with foods were quick to take advantages of SFC. Early on, it was used for fairly nonpolar mixtures, like fats and oils, oil-soluble vitamins, tocopherols, and sterols.
Innovations in SFC mobile phases have opened up much more polar application areas to SFC. These include peptides, free fatty acids, phospholipids, polyphenols, natural antioxidants, small carbohydrates, and alkaloids, to name but a few.
SFC and SFC/MS have also been used to separate and determine food contaminants, such as dyes that are not allowed in food, and process-derived contaminants, such as MCPD and glycidyl esters. The future of SFC in the food industry is bright.
Household and Consumer Products
Scientists in the household and consumer products industry were some of the earliest industrial scientists to take advantage of SFC. These products often contain a complex mixture of surfactants and polymers. The polymers themselves can be extremely complex, with a variety of repeating units and a wide range of chainlengths, blocks, and endgroups. The polymers included surface-protecting agents, soil-release polymers, complexing agents, shine-enhancing actives, etc.
The ability to use multiple columns in SFC allows high resolution characterization of the polymers, and provides powerful structure-activity relationships for these polymers.
While SFC has been used to characterize small polymers from many industries, its use in the household and consumer products area has been a shining example of its power.
Natural Products and Essential Oils
For more than a century, natural products of commercial interest have been isolated using a variety of means including extraction, distillation, crystallization, and, in some cases, chromatography. In the late 1970’s, the large-scale application of SFE utilizing carbon dioxide to remove caffeine from coffee was deployed. Since then, thousands of other natural compounds and extracts have been derived commercially via SFE.
Starting in the 1990s, packed column SFC has also been employed utilizing carbon dioxide with other co-solvents to further purify natural products especially of medicinal interest. A more recent example includes the SFC analysis and separation of various cannabinoids from SFE-derived cannabis extracts. SFC-MS has also been used, in addition to the more traditional GC-MS approach, for the analysis and identification of essential oils.
Personal Care Products
There are many uses of SFC in the vast market of personal care products which exemplify the powerful technique’s versatility.
Just as with pharmaceuticals, many personal care actives are chiral in nature. Monitoring the presence of the various enantiomers in cosmetics, sun protectants, fragrances, and lotions can be extremely important in evaluating product quality and ensuring product consistency and effectiveness.
In addition to chiral applications, achiral analysis of various excipients, emulsifiers, polymers, and surfactants plays an important role in personal care product development.
Last but certainly not least, an important application of SFC in the personal care markets is the monitoring of chemical species known to be or suspected of being toxic to humans or pets.
The use of SFC in the personal care market is growing at an extremely fast pace and it will be exciting to watch what the next round of applications delivers.
The use of SFC within the pharmaceutical industry has exploded over the past 25 years. In the 1990s, SFC was first identified as a method for the preparative resolution of enantiomers. Since the first purifications, this application has grown to where it is now the preferred technique for small scale (< 1 g) resolution of enantiomers.
This growth is due to the main advantages of SFC over LC, including speed, reduced solvent utilization and waste generation, higher purification throughputs and reduced separation costs.
While preparative SFC has been utilized for 20-plus years in the pharmaceutical industry, it is only over the past decade that analytical SFC has moved beyond pharmaceutical discovery into validated applications found in development and manufacturing. This is due to advances in analytical SFC equipment as well as increased research that has placed SFC at the same level as HPLC in terms of sensitivity and ease of use, often with decreased analyses times.