Long Term Storage of Air Samples - A Study of Two Bag Materials 2000-01-2502
Concentrations of six organic gases/vapors were monitored over a period of 90 days in two popular styles of polymer sample bags. The test species were selected to cover many different chemical properties and included aromatic, aliphatic, chlorinated aliphatic, alcohol, non-chlorine refrigerant and ketone structures. The two bag styles were (1) single layer Tedlar, and (2) Multilayer (polyethylene on the inner (sample side) surface and an intermediate layer of aluminum). The two bags exhibited different storage properties. The Tedlar bags showed only gradual losses with little initial adsorption on the bag surface. The Multilayer bags exhibited virtually no diffusive loss, but in some cases significant loses due to adsorption. For short term storage of up to several days, the Tedlar bag is preferred. For long term storage of several weeks to months, the Multilayer bag is necessary, but will not provide true values of the initial concentrations. The possible implications of this study to the myriad of industrial needs for gas sampling and sample preservation are obvious.