The {open_quotes}Cone-GC{close_quotes} was developed in response to a need for down hole, in-situ characterization of volatile organics within the soil profile, in the vadose zone, or a water headspace. A design based on the use of a miniature gas chromatograph was selected since it was believed that such an instrument would be adaptable to a broad range of analytes and could be used in complex, real-world situations where the environmental contaminants to be monitored may exist in complex mixtures with other vapors. The Cone-GC is versatile and will also fit within many other soil probes, hole liners, and minimally intrusive emplacement systems where small size in addition to high performance are required. The Cone-GC was designed to allow environmental specialists for the first time to obtain immediate, in-situ chemical measurements in a soil probe and to make real-time, on-site decisions that will greatly reduce the time (and cost) of site characterization and remediation. It will no longer be necessary to collect samples (using long sampling lines that may become contaminated), send them to an off-site laboratory for analysis, and then wait hours or days for results.