Evaluation of Sampling Methods for Gaseous Atmospheric Samples

摘要

A research program was conducted to test and evaluate several alternatives for collecting and transferring samples from the collection site to the laboratory for the analysis of a variety of toxic organic pollutants by gas chromatography (GC). Sample storage media included three types of polymeric bags (FEP Teflon, Tedlar, five-layered aluminized bags), glass bulbs, electropolished and Summa polished cannisters, Tenax GC and charcoal cartridges, and nickel cryogenic traps. Twenty-seven test compounds including hydrocarbons, aromatics, halogenated hydrocarbons, halogenated aromatics, and oxygen, nitrogen and sulfur-containing compounds were used to test the storage media. Dynamically flowing mixtures of these gases were synthesized using a specially designed permeation/dilution system. Quantitative laboratory stability tests were conducted with Tenax GC, charcoal, and cryogenic traps at 2 concentration levels of 50 parts per billion (ppb) and 200 parts per trillion (ppt), for 15 of the 27 chemicals. Quantitative stability tests were conducted with the remaining storage media at one concentration level, nominally 50 ppb, for the same 15 chemicals. The stability tests were conducted over a 7 day storage period. The potential effect of inorganic gases as interferences during the collection of test compounds was quantitatively studied. An automatic two channel ambient air sampler utilizing sorbent cartridges as the collection medium was also designed and fabricated. A quality control and quality assurance (QC/QA) program was established and maintained for all measured and analyzed data.