Automated cryogenic preconcentration and gas chromatographic determination of volatile organic compounds in air

Multi-adsorbent Preconcentration and Gas Chromatographic Analysis of Air Toxics with an Automated Collection/Analytical System

“…The glass-bead trap collection and desorption temperature set points give optimal recovery of the VOCs of interest without causing trap plugging problems associated with excessive cooling or trap bleed due to excessive heating. 4 The temperature set points for the multi-adsorbent traps are those sugCopyright 1991-Air & Waste Management Association gested by the supplier when it is used in a purge and trap instrument. A Valco Model A602 air actuator drives the 6-port valve from the sample collection to sample injection positions.…”

“…The use of this type of dryer has been shown to have no affinity for the 41 VOCs of interest in this study. 4 -5 ' 8 The multi-adsorbent trap is installed so that there is sample flow initially through the Carbopack B material and then through the Carbosieve S-III. During desorption, the trapped VOCs are backflushed off" the trap.…”

Enhanced Performance of Nafion Dryers in Removing Water from Air Samples Prior to Gas Chromatographic Analysis

“…6 A set of experiments was performed to determine the effects of such treatment on dryer performance under actual sampling conditions.…”

“…The methodology has been described elsewhere. 6 " 8 Cryogenic trapping has been shown to be a preferred preconcentration technique, particularly for the lighter VOCs, i.e., Ci, C2 and C3 compounds. 13 These compounds tend to have low breakthrough volumes on the solid sorbents (such as Tenax-GC) that are t)ften used as preconcentration media.…”

“…17 " 21 The use of these dryers has already been validated for our sampling conditions and compounds of interest, i.e., selected light, nonpolar hydrocarbons and halogenated hydrocarbons of environmental concern. 6 For convenience, the dryers used in our laboratory were purchased pre-assembled with fittings and purge tubing from Perma-Pure Products, Inc. (Farmingdale, NJ). This paper describes a novel dryer cleanup technique that can be implemented during the non-sampling portion of a GC analysis cycle.…”