EC-09. Characterizing Influence of PTFE-coated Neoprene Diaphragm Material for Sampling Pumps on Trace Gas Measurements

Abstract
Continuous monitoring of our atmosphere through discrete air sampling is an essential activity to the mission of NOAA’s Global Monitoring Laboratory (GML), allowing for the characterization of atmospheric composition. Ensuring samples are representative of original composition is critical to the integrity of the long term records produced by GML. Scientists at GML analyze ~70 trace compounds whose atmospheric mole fractions range between 100’s of micromoles per mole (10-4 mol mol-1) down to 100’s of femtomoles per mol (10-13 mol mol-1). Sample capture, storage, and transport have the potential to influence and contaminate sample analytes. It is critical that we understand and characterize the influence of all components in the sampling system when selecting equipment. Typically, piston-driven diaphragm pumps are used to draw the sample through a long inlet suspended above the ground and pressurize the air into a stainless steel or borosilicate glass flask for future analysis. Because all sampling pumps of this type use semi-permeable polymers, there is potential for these materials to affect some of the analytes measured by GML. We present results from a series of tests using a pump with a PTFE-coated neoprene diaphragm KNF Neuberger Model N86 pump and characterize the impact of this material on a subset of trace species measured by GML’s Long-term Observations of Greenhouse gasses and Ozone-depleting Substances (LOGOS) Division.