OnColumn Interface

The on-column interface is used for the transfer by partially concurrent evaporation (see Figure 1).

LC detector t0 waste

=Cf Transfer valve

Carrier gas

Early vapour GC detector

injector tt U

Uncoated Retaining "Separation pre-column pre-column column (retention gap) (3 m x 0.32 mm) (10 m x 0.53 mm)

Figure 1 On-column interface for samples containing highly volatile solutes.

Transfer occurs by the same principles as on-column injection of large volumes (retention gap technique). The eluent from the LC passes through a valve for selecting the fraction to be introduced into the GC. It then enters an uncoated pre-column of typically 10 mx 0.53 mm i.d., with a capacity of retaining 100-250 |L of wetting liquid. Partially concurrent evaporation ensures that LC fractions with larger volumes do not overfill the uncoated pre-column. Mostly a retaining pre-column (2-3 mx 0.32 mm i.d.) has been used, but if the early vapour exit is closed before the end of solvent evaporation, it is not really needed. The technique has been routinely used for fractions of up to 800 | L volume.

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Solar Panel Basics

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