Analysis of breath alcohol via infrared spectrophotometry: predicting false ethanol results by application of the base-line method to vapor phase infrared spectra.

Toluene and a mixture of the isomeric xylenes are common organic solvents that have been implicated in false ethanol results produced by older models of the Intoxilyzer 5000, a breath alcohol analyzer that uses infrared spectrophotometry to quantitate ethanol in breath samples. A straightforward method is described which predicts this type of interference in analyses conducted on such models. The methodology relies on a comparison of the vapor phase infrared spectra of toluene and xylene with the corresponding spectrum of ethanol, using the base-line method to estimate relative absorbances at the two analytical wavelengths employed by the Intoxilyzer 5000. The point is also made that, given the potential for such interference, a model of the Intoxilyzer 5000 has been developed that has the capability to compensate for this problem.