Atmospheric non-methane volatile organic compounds (VOCs) are known to play an important role in urban ozone formation during the summer. To respond to the need for a direct measure of VOC source contributions from biogenic ((14)C/(12)C=10 to the -12 power) and fossil fuel ((14)C/(12)C=0) emissions, a system and protocol are being developed to separate the total VOC fraction from 0.1 cu m of ambient air for accelerator mass spectrometry (AMS) (14)C. The gas separation system developed at NIST allows for the simultaneous separation of low vapor pressure (LVP) VOCs and H2O, high vapor pressure (HVP) VOCs and CO2, CO and CH4 through sequential cryogenic separation and selective oxidation techniques. Preliminary results of this system and procedure for isolating these fractions show a LVP-VOC blank of 2 + or - microgram C, which represents the effect of the separation system plus CO2 cross-contamination. Hydrocarbons having vapor pressures greater than n-decane are not retained at a level of more than a few percent in the LVP-VOC fraction. The recovery of C5-C8 hydrocarbons in the combined HVP-VOC and CO2 fraction ranges from 27% to 78%.