What Interfering Substances Are There in Breath.pdf

1 What Interfering Substances Are There in Breath of Apprehended Drivers? Experience Using a 5-Filter Infrared Analyzer (the Evidenzer). Alan Wayne Jones*1 and Lars Andersson2 1Department of Forensic Genetics and Forensic Chemistry, Artillerigatan 12, 581 33 Link?ping and 2National Laboratory of Forensic Sciences, Link?ping. Sweden. Abstract Infrared spectroscopy is the analytical principle incorporated into many of the latest generation of evidential breath-alcohol instruments. In Sweden, for example, the instrument approved for legal purposes is the Evidenzer, which measures a person’s breath-ethanol concentration (BEC) by means of 4-infrared filters (3.3 to 3.5 micron). However, this kind of infrared technology is not completely specific for identification of ethanol and the claim is sometimes made that other volatiles present in the breath sample caused a falsely high reading. This defense argument relates to the specificity of the infrared analysis and its response to interfering substances. The volatile organic substances (VOCs) most frequently identified in blood when an interfering substance was indicated in breath were acetone, isopropanol and methyl ethyl ketone (MEK). However, in most of these cases the blood and breath samples also contained appreciable concentrations of ethanol above the legal limit for driving. Acetone and isopropanol might arise during ketogenesis in people suffering form diabetes or after eating low carbohydrate diets. Consumption of denatured alcohol spiked with acetone and other ketones can also trigger the Evidenzer to flag for an interfering substance. The evidential breath tests with Evidenzer were aborted only 27 times owing to an interfering substance (N = 24,072 tests). Elevated concentrations of ethanol, acetone, isopropanol and/or MEK were present in most blood samples and arose from drinking denatured alcohol. The defense argument that substances in breath other than ethanol are a common occurr