A small-volume constant-flow air sampling device for thermal desorption GC analysis

A glass syringe with disposable membrane filters was tested as a constant-flow air sampling device. The principle of this sampling device is straightforward: when the syringe is inverted vertically, the syringe plunger falls at a constant speed if an appropriate flow restrictor is connected at the syringe inlet. In case of a 100 ml syringe with two Teflon membrane filters of 0.50 microns in pore size and 3 mm in diameter, the flow rate was 3 ml/min. The flow rate was constant for a 15-minute sampling period when two to eight filters were used as a flow restrictor. A sample volume of less than 50 ml is sufficient for the determination of organic solvent vapor at the ppm level, when gas chromatography with thermal desorption method is employed. Therefore, this sampling device is useful for determining the time-weighted average concentrations of organic solvent vapor in a working environment.