GB1324352A - Sample injection in gas chromatography - Google Patents

Abstract

1324352 Sample injection system for gas chromatography IMPERIAL CHEMICAL INDUSTRIES 27 July 1970 [14 Aug 1969] 40648/ 69 Heading B1X Gas pressure or flow controllers 1, 7 through which separate carrier gas streams flow, are set together with needle valve 12 so that with valve 13 open a slightly higher pressure is imposed at junction 2 than would arise from flow through controller 7 alone. Under such conditions, gas from controller 7 passes in turn through pre-heater 8, detector 9, line 11, and valve 12 before venting through valve 13, while gas from controller 1 passes in turn through column 3 and flame ionisation detector 4. The sample is injected by syringe at 8 where it is vaporised. The plug of sample vapour is detected as it passes through detector 9, which generates a pulse in pulse generator 10 operating time delay switch 14. As the plug approaches line 11, switch 14 operates solenoidactuated valve 13, causing the plug to pass along line 6 to and through column 3. After a further preset period, switch 14 opens valve 13, thereby venting the remainder of the sample through valve 13. In this way, reproducible time-controlled quantities of sample are applied to column 3. In an alternative embodiment (see Fig. 2, not shown), controllers (20, 21) are set to provide a somewhat higher carrier gas pressure in line (27) than in line (23). Sample is injected through sample vaporiser (22), contacts on the syringe actuating time delay switch (29). As the plug of sample passing along line (23) approaches line (24), switch (29) operates to shut valve (28), the effect of flow restrictor (26) in line (23) then being to cause part of the sample plug to pass along lines (24, 30) to and through column (31) and flame ionisation detector (32). Again, after a further pre-set period, switch (29) opens valve (28), causing the rest of the sample to vent through restrictor (26).