The low concentrations (ppm to ppb) typical of organic pollutants dissolved in groundwater have been a major factor limiting the application of stable isotope tracing techniques at contaminated field sites. In this study, pentane extraction of benzene, toluene, ethylbenzene, and the xylene isomers (BTEX) from water is shown to be an excellent means of resolving this problem and preparing low concentration samples for carbon isotope analysis using high sensitivity gas chromatograph/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Pentane extraction provides accurate, reproducible, and linear isotopic results for dissolved BTEX in water with concentrations ranging from 0.1 to 100 ppma range typically found in contaminated field settings. It is a rapid and flexible technique for extracting the monoaromatics from water and can readily be adapted to extract other organic contaminants. Demonstration of the feasibility of this technique for sparingly soluble BTEX compounds paves the way for applications o...