The stability of volatile organic compounds in environmental water samples has been studied, particularly with respect to the establishment of preanalytical holding times. Methods have been developed for the preparation of standard samples containing known concentrations of volatile organics. Three water samples were used: distilled water, surface water, and groundwater. Samples were stored at both room temperature and under refrigeration. Data were collected over a 365-day period by gas chromatography /mass spectrometry. In water samples containing low chloride content (distilled water), rapid dehydrohalogenation of tetrachloroethane to trichloroethylene occurred. Such degradation was also evident in the surface water and groundwater samples stored at room temperature. A less rapid conversion of trichloroethane to dichloroethylene occurred in distilled water samples stored at 25 °C. Reduced concentrations of aromatic volatiles were observed in both surface and groundwater matrices after 28 days. Loss of carbon tetrachloride was also apparent in surface water samples stored at room temperature. Subsequently, experiments were conducted to determine the value of reduced pH in sample preservation. It was shown that acidification with hydrochloric acid effectively prevented degradation and allowed indefinite storage. However, sampling and analytical considerations make the use of HC1 impractical. Therefore, a study was carried out using sodium bisulfate and ascorbic acid as preservatives. Both substances effectively preserved the samples, but sodium bisulfate proved to have several advantages over ascorbic acid. Samples preserved with either acid were stable over the 112-day experimental period.The implication is that with preservation the maximum holding times for such samples will be limited only by the need for sample turnaround.

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Methodology was developed to reproducibly prepare performance evaluation materials for volatile organics analysis in soils and waters. Tedlar gas sampling bags are used to prepare the volatile organics spike solutions. The bags allow large volumes of sample or spike solution to be prepared to a high degree of homogeneity while using less methanol. Preparation of a large volume of sample or spike solution allows for increased accuracy of fortification. The accuracy is generally ±20% or better, and the precision is generally ±10% or better for water samples. The precision for preparation of soil samples is also good, but the accuracy suffers from variable recovery efficiencies from the soils. Most volatile organics were well preserved in 3 water samples by storage at refrigerator temperature for 14 days.

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