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CO2 Chromatography

Updated: Jul 22

Supercritical Fluid Chromatography (SFC) with CO2 is commonly used for achiral separations and purifications in the pharmaceutical industry.[1] The benefits of this technology are wide ranging. CO2 alone is a mobile phase that allows separations to occur at lower temperatures, ideal for botanical properties such as terpenes that are volatile with hotter temperatures. There is a wide choice of stationary and mobile phases, chiral and achiral separations, and gradient capabilities across widest polarity range. Additionally, there is a major reduction in the hazardous solvent used if any is needed for your application, and cost savings on solvents and time.


Essential Extraction Corp’s Patent Pending Little Buddy CO2 Re-circulator with SFC column utilizes carbon dioxide gas directly from a pressurized gas cylinder. The system then automatically condenses the CO2 gas into a liquid which uniformly fills the column, temperature control is applied to the column to raise the pressures in the column forcing material through filters and media.


Due to the nature of CO2 in a supercritical phase being both at once a liquid and a gas, SFC chromatography has the combined benefits of a liquid to dissolve the medium matrix and also an inert gas to push material through filters and media. Typically, eluent strength is increased by using a polar co-solvent such as methanol, possibly with a weak acid or base at low concentrations ~1%. The solvent strength of CO2 can be increased by increasing density or using a polar cosolvent, however in doing so the fraction of cosolvent takes over the CO2 as the mobile phase. Cosolvents are typically simple alcohols like methanol, ethanol, or isopropyl alcohol. Especially for food-grade materials, the selected cosolvent should be ethanol or ethyl acetate, both of which are generally recognized as safe for food production.


The Little Buddy CO2 Re-circulator SFC system delivers optimal control of pressure by means of an automated back pressure regulator. From an operating standpoint, SFC is as simple and robust as HPLC but fraction collection is more suitable because the primary mobile phase evaporates leaving only the analyte and a small volume of polar co-solvent. With Essential Extraction Corp’s Little Buddy CO2 re-circulator, the outlet CO2 is captured, recompressed, and recycled, allowing for >90% reuse of CO2. Moreover, as the Little Buddy system releases the CO2 back into a gas phase to be re-condensed or re-collected it separates gas/liquid and the heavier botanical material remains in the bottom of the collection vessel.




References

White, Craig; Burnett, John (2005). "Integration of supercritical fluid chromatography into drug discovery as a routine support tool". Journal of Chromatography A. 1074 (1–2): 175–185. doi:10.1016/j.chroma.2005.02.087. ISSN 0021-9673.


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