Gas chromatography/mass spectrometry response pattern analysis of volatile organics in soils
Abstract
The purge-and-trap gas chromatographic/mass spectrometric methods used by government agencies and their contracting laboratories for the analysis of volatile organic compounds in soils require the addition of both surrogate and internal standards to the sample matrix just prior to purging the sample with an inert gas. Addition of the standards at this point in the analysis provides no information regarding the effect that the sample matrix has on the target compounds, with a resultant artificially low calculated value for the target compounds; Addition of surrogate standards to the sample matrix at the same time as the target compounds reveals patterns of response indicating which surrogates should be associated with which target compounds. Response ratios generated from these target/surrogate pairs are then applied to subsequent sample analyses within the same soil type, providing recoveries of 90-105% with low relative standard deviations; Samples spiked with target compounds then spiked with surrogate compounds three days later, provided the same accuracy and precision when analyzed at holding times of zero, two, and three days after the surrogate spike.