This project explores the feasibility of an innovative new on-line analysis method for volatile organic compounds (VOCs) and their oxidation products. In a collaborative project between investigators at University of California - Davis and University of North Carolina an atmospheric sampling glow-discharge ionization/quadrupole ion trap mass spectrometer (ASGDI/QITMS) will be modified then challenged in a number of laboratory experiments to quantify sensitivity to and selectivity of VOCs and oxygenated VOCs at levels representative of the ambient natural atmosphere. The broader impact of this project involves demonstration of a potentially innovative new technique for selective measurement of a variety of critically important compounds playing key roles in ambient photooxidation cycles; ozone and secondary aerosol formation; human health and habitability; and climate. The full-time directed research work of a graduate student is supported by the project.