Instrumentation

Figure 2 illustrates the instrumentation for SFC. The mobile phase is pumped as a liquid and the pressurized fluid passes, via an injection valve, into the column maintained in an oven at a temperature above Tc, and then to a detector. A pressure restrictor to maintain supercritical conditions is located either after the detector or at the end of the column.

Figure 2 Schematic diagram of an SFC instrument.

Table 2 Columns in SFC

Column

Internal diameter (mm)

Advantages

Disadvantages

Conventional Microbore Packed capillary Open tubular

High capacity Rapid analysis Highly selective Low capacity, high resolution inactive

Low overall efficiency Highly activity

Long analysis times Selectivity only conferred by stationary phase

Conventional HPLC pumps with cooled heads were used from the start for SFC in packed columns. Syringe pumps were initially used in capillary SFC because of their pulseless operation. Small column diameters necessary in capillary SFC make the method of sample introduction important; small volumes and rapid injection are achieved by a pneumatically operated loop valve with electronic timing.

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Solar Panel Basics

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