Super Critical Fluid Chromatography

Supercritical Fluid Chromatography - Instrumentation
A supercritical fluid chromatography instrument consists of a mobile phase container, an injector, a column in an oven, a restrictor and a detector. The components are similar to those of a gas chromatograph with exception of the restrictor. The restrictor is needed to maintain the pressure above the critical point. If the detector is a gas-phase detector working at atmospheric pressure (e.g., Flame Ionization Detector FID) the restrictor is placed before the detector. When using a detector that works under supercritical conditions (e.g., Ultra Violet detector UV) the restrictor is placed after the detector.
 
Detection limit | Gas recommendation | Regulator recommendation |
≤ 1 ppm | HiQ Carbon dioxide 4.5 SFC | BASELINE C106 series |
Supercritical Fluid Chromatography (SFC) |

Mobile phases
The most widely used mobile phase for supercritical fluid chromatography is carbon dioxide because it is an excellent solvent for a variety of organic molecules. A number of other substances have served as mobile phase including ethane, pentane, nitrous oxide, dichlorofluormethane, diethylether, ammonia and tetrahydrofuran. 

Columns
Both open-tubular and packed columns are used for SFC. The open-tubular columns are most useful for separations requiring high-efficiency separations and for complex samples. Packed columns are most useful for high-speed separations requiring a moderate column efficiency and for samples containing fewer components. 

Detectors
When using capillary columns and carbon dioxide practically all Gas Chromatography (GC) detectors and many High Performance Liquid Chromatography (HPLC) detectors can be used. With packed columns and organic modifiers the number of detectors available is more limited. The Flame Ionization Detector (FID) is the most frequently used detector. Other detectors that often are used are Flame Photometric Detector (FPD), Electron Capture Detector ECD and Mass...