A long-term field experience with breath ethanol collection employing silica gel.

Breath specimens (N = 143) from human subjects initially analyzed for ethanol content by infrared spectroscopy were collected onto silica gel. The specimens were retained 1.25 to 2.75 years following adsorption and subsequently analyzed by headspace gas chromatography. The results revealed good overall correlation between the direct and delayed ethanol determinations (r = 0.900). Specimens were collected by police officers following a defined protocol and the results are presented to illustrate practical use and limitations of such a technique.