Abstract View
Enriching Inlet for Improving Sensitivity and Level of Detection of Reactive Organic Gases by an Order of Magnitude in SCCM-Level Flows
NAMRATA SHANMUKH PANJI, Graham Frazier, Gabriel Isaacman-VanWertz, Virginia Tech
Abstract Number: 239
Working Group: Instrumentation and Methods
Abstract
A significant portion of the global aerosol load is due to organic aerosols (OA), which are formed in large part when reactive organic gases in the atmosphere, such as terpenes, are oxidized through complex photochemical pathways. Quantitative measurement of these compounds, especially using low-cost methods, is challenging because they are present in sub-ppb to sub-ppt levels. Furthermore, losses to instrument lines and surfaces can compound these challenges. As a result, instruments measuring volatile reactive organics often suffer from high levels of detection and low sensitivities. We have developed a novel enriching inlet to concentrate these gases (by up to an order of magnitude) for low sampling flows. VOCs are sampled through Teflon™ AF-2400 tubing subjected to a pressure differential. Under these conditions, inert gases are driven out of the sampling stream due to selective permeation, leaving behind a stream of concentrated VOCs for analysis downstream. We present here a validated model that links pressure differential, inlet length, sampling flow rate, and analyte permeability, to predict enrichment of a given gas at a given sample flow, with propane (C3H8) used as a sample gas. We demonstrate this inlet with enrichment of up to a factor of 10 for a wide range of atmospherically important analytes, including major OA precursors like isoprene (C5H8) and α-pinene (C10H16). Enrichment is shown to be predictable, and achievable under a wide range of pressurized and sub-ambient flow conditions.