Optimizing Sensitivity of SIM Mode of GC/MS Analysis for EPA’s TO-14 Air Toxics Method

Guidelines for determining volatile organic compounds (VOCs) at ambient levels In air are published In Method TO-14 ol the U.S. Environmental Protection Agency’s “Compendium 01 Methods lor the Determination of Toxic Organic Compounds In Ambient Air.” To achieve the sensitivity required for sub-part-per-bllllon-by-volume (ppbv) determinations of VOCs, TO-14 recommends selective Ion monitoring (SIM) mode of operation when a conventional quadru-pole mass spectrometer Is used as the analytical finish. This paper describes the Implementation of SIM mode of analysis and presents the rationale and methods for optimizing SIM parameters for maximum sensitivity when analyzing whole-air samples for trace levels of targeted VOCs.