Method to predict gas chromatographic response factors for the trace-level analysis of volatile organic compounds based on the effective carbon number concept.

A procedure has been developed to estimate GC-MS response factors based on the theory of effective carbon number defined as the sum of the carbon number and carbon number equivalent for each selected molecular descriptor (multiplied by its number of occurrences) in each compound's molecular structure. As a means to validate the effective carbon number procedure for GC-MS analysis, a test suite of 19 volatile organic compounds was analyzed by the sorbent-tube thermal desorption method. In the effective carbon number procedure, the carbon number equivalent for each descriptor was determined to yield the optimal linear plots between response factor versus the effective carbon number with the maximum R(2) (>0.975) and the minimum mean absolute error (<5%). Effective carbon number analysis is validated as a potent approach to estimate response factor values for most compounds amenable to the sorbent-tube thermal desorption GC-MS method. Overall, it is concluded that the application of response factor versus effective carbon number relationship can produce fairly reliable prediction with reduced errors relative to other comparable procedures such as the response factor versus the carbon number approach.