GB906121A - Improvements in or relating to liquid sampling for gas chromatography - Google Patents

Abstract

A liquid sample is introduced into a stream of carrier gas for passage to a gas chromatograph column by filling a micro-pipette 15 or 42 with the liquid, placing the pipette in a bore 11 or 40 of a rotatable valve body 10 or 34, discharging the pipette so that the residue of liquid on the walls forms the sample and rotating the valve body so that the pipette and sample are brought into contact with the carrier stream. As shown in Fig. 2, the filled pipette is fitted in a holder 16 having a springy slotted end and the holder is screwed into the <PICT:0906121/III/1> <PICT:0906121/III/2> bore 11. The pipette is then discharged by holding against it an absorbent wad 28 pressed out from a holder 26 by a pusher member 29 and is pushed back into the holder by extra pressure on the holder 26. Finally the valve body 10 is rotated through 90 degrees so that the bore 11 connects the gas conduits 8, 33. In Fig. 8, the valve body 34 is rotatable on pins 38 on an axis parallel to the conduits 35, 36 or oblique to them so that the bore 40 slopes downwards, and the pipette 42 is retained in position by a spring-loaded pin 43. When the valve body is in the loading position, the carrier gas stream is maintained through a bore 12 passing behind the bore 11 or through a bore 41 which may be of horseshoe section to reduce the time of interruption of the stream during rotation of the valve body. Heat may be applied to the sample, either directly or by preheating the carrier gas by means of a coil 44.