SUPERCRITICAL FLUID CHROMATOGRAPHY:INSTRUMENTATION
Hai friends ,as my team members have explained about the introduction part of Supercritical fluid chromatography I am going to explain about the instrumentation part.
Supercritical fluid chromatography
Supercritical Fluid Chromatography equipment consists of a gas supply (1), a high pressure pump (2), the analytical column (5) in a oven which is thermostat-controlled one(4), a restrictor to maintain the high pressure in the column, an injector (3) and a detector (6)
Supercritical fluid chromatography Instrumentation
1) Gas supply or Mobile Phase:
Cost, interference with chromatographic detectors and physical properties like nontoxic nature, nonflammable, low critical values are considered while selecting a mobile phase. Carbon dioxide is the ideal to satisfy all the above properties. The main disadvantage of it is very polar or ionic compounds are not able to be eluted. A modifier fluid is used to over come this problem.
Here mainly flow control is necessary so Syringe pumps are used for capillary SFC for consistent pressure and for Packed columns for easier blending of the mobile phase or introduction of modifier fluids reciprocating pumps are used. .
In capillary SFC small sample should be quickly injected into the column and so pneumatically driven valves are used. For packed SFC a typical injection valve is commonly used.
4) Oven :
Conventional GC or LC ovens are used
Two types of analytical columns are used in SFC i.e. packed and capillary. Packed columns contain small deactivated substances to which the stationary phase adheres. These are conventionally stainless steel. Capillary columns are open tubular columns made of fused silica which have small internal diameter.
Flame ionization detectors and FPD, liquid-phase detectors like RID, ultraviolet-visible spectrophotometric detectors and light scattering detectors have been employed for SFC.
7) Back-Pressure Device or Restrictor:
It is used to maintain the desired pressure in the coloumn.
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