Page 7 - Application Handbook - Liquid Chromatography

LAAN-A-LC-E272

Application Supercritical Fluid Extraction / Chromatography

News Analysis of Unstable Compounds Using Online SFE-SFC

No.L496

Supercritical fluids have characteristics of both gas and Previously SFE and SFC were offline operations for
liquid; low viscosity, high diffusivity and solubility. In pretreatment or analysis, respectively, and treated as
particular, carbon dioxide becomes a supercritical fluid at completely separate workflows. However, now SFE
a relatively modest critical point (31.1 °C and 7.38 MPa). and SFC can be connected online using the Nexera UC
Due to its low toxicity, inertness, easy availability, and low system, which allows integration of all the processes
cost, supercritical carbon dioxide fluid is used in a wide from pretreatment to data acquisition into a single
variety of fields. Analytical applications using it include workflow. This article describes using the Nexera UC
supercritical fluid extraction (SFE) and supercritical fluid system for online SFE-SFC analysis.
chromatography (SFC).

n Online SFE-SFC
A flow diagram of online SFE-SFC analysis is shown in within a single system, which eliminates the need for
Fig. 1. Online SFE-SFC involves online introduction of any complicated pretreatment processes and enables
components extracted from an extraction vessel using automation. That can significantly reduce the time and
supercritical fluid to an SFC analytical column, where effort required for the various operations involved in the
they are separated and then detected accordingly. The analysis.
entire process, from extraction to data acquisition, is It also means that the entire process, from extraction
performed by switching flow lines using a valve inside the to separation and detection, can be performed without
SFE unit. Two types of extraction operations are involved. exposure to light, without oxidation, and in a moisture-
After supercritical fluid is introduced to the extraction free environment. Therefore, the method is extremely
vessel, static extraction is performed where components useful for analyzing unstable compounds, such as
are extracted while fluid flow is stopped. Then dynamic compounds with components easily decomposed by
extraction is done to extract components while pumping light, easily oxidized, or easily hydrolyzed. Unlike offline
fluid through the extraction vessel. In the case of online SFE, online SFE-SFC eliminates need for preparing
SFE-SFC, the sample is transported through the analytical sample solutions, which means it eliminates possibility
column during dynamic extraction. of dilution of target components by the sample solvent,
Consequently, the entire online SFE-SFC process, from thus providing an easy way of increasing sensitivity.
extraction to separation and detection, can be completed

More than Ambient
CO2 Pump Extraction Vessel 10 MPa pressure
Analytical column

Valve Valve
Oven UV-VIS Back pressure
SFE Unit Detector regulator
Liquid-CO2 Modifier
Cylinder Pump

From To
Pumps Column
ᶃ Standby ᶄ Static extraction ᶅ Dynamic extraction ᶆ Analysis

Fig. 1 Process Flow Diagram of Online SFE-SFC System