Chemical preservation of volatile organic compounds in soil

Laboratory protocols are necessary for assessing the concentration stability of volatile organic compounds (VOCs) in site-specific soil matrices, because refrigeration (4 degrees C) alone does not prevent microbiological degradation. An experimental approach was developed using hermetically sealed vials for storage and in-vial analysis. This technique avoids volatilization losses while assessing the apparent rate of microbiological degradation and enables an assessment of the effectiveness of chemical preservation. Using this approach, concentrations of most of the chlorinated compounds tested were unaffected by storage temperature and/or chemical preservation over a 28-day holding period. Aromatic compounds, however, were rapidly degraded (>95% loss) when stored at 22 degrees C over this same period and often showed a substantial reduction (30% or greater loss) when stored at 4 degrees C. Chemical preservation with either sodium chloride (NaCl) or sodium bisulfate (NaHSO4) suppressed the microbiological degradation of these aromatic compounds in samples held at 22 degrees C.