An automated flowing system for measuring and recording carbon dioxide production by infrared spectrophotometry has been described (3). This system has now been coupled tb a gas chromatograph for analysis of the ethylene production of apple fruits using the same overall system, respiration chambers and sample size. Instrumentation is as follows: gas chromatograph, Beckman GC-5 with dual flame ionization detectors; column, 10 ft, { inch (3.05 m,0.32 cm) stainless steel packed with silica gel of mesh 60'80; column temperature, 180"C (isothermal); helium flow rate,75 ml per min; recorder, Beckman 10-inch (25.4 The effiuent from the sample cell of the IRA passes into the sample valve of the gas chromatograph. In the purging position of the slider, the Por$ are aligned-so that the effluent passes through the sample loop to the atmosPhere, rv6ile the carrier gas passes directly into the column (Fig. t-A). When the cam timer closes the cbntrol circuit, the interval timer, solenoid and pneumatic activator are energized, causing the slider to move. In this position of the slider the carrier gis enters the sample loop and injects the 3-ml sample into the column (Fig. 1-B). The efluent from the IRA is vented, with only momentary interruption, to the atmosphere. The time interval for clearing the valve of the sample ( 12 seconds in our application) depends on the setting of the interval timer.-At the end of the 12 ieconds when sample injection is complete, the interval timer breaks the control circuit to the solenoid and the slider returns to its original position. This permits the effiuent from the next respiration chamber ielected by the overalf sampling system (3) to florv through the loop. While the loop is being filled with a sample from the respiration chamber currently in the sampling system, the sample previously injccted Passes through the column and detector, and the response is recorded.The interval timer is used for control of the sample valve instead of the cam timer, for the following reasons: l. The interval necessary for clearing the valve of the sample can be changed rapidly and easily by rotating a setting arm on the dial of the interval timer, to permit different times r,vith different-sized sample loops as necessitated by changes in plant material, flow rate and sample size.'Model P-1M Industrial Timer Division
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.