Myth #13: Breath Test — Breath Tests Are Specific For Ethanol
A number of studies found substances that can interfere with an infra-red testing device that were not picked up by the instrument.
We conclude that the Intoxilyzer Model 4011 AS may exhibit significant interference when used for subjects previously exposed to lacquer or lacquer thinner fumes.
William Giguiere, David Lewis, Randall C. Baselt, Randall Chang, Lacquer fumes and the Intoxilyzer, 12 Journal of Analytical Toxicology 168, 168 (May-June 1988).
Defending against DUI / DWIToluene alone can account for somewhere between 0.048 and 0.058 g/210L of the ostensible ethanol reading without causing the interference mechanism to trigger (Table 2), and this value would be below most legal threshold. However, if the signal resulting from toluene is augmented by the presence of genuine ethanol, the readout could exceed legal limits without activating the interference mechanism. The results of this study clearly indicate that all five substances tested for potential interference with the Intoxilyzer 5000 will interfere to some degree. Even so, the performance of this instrument is significantly better than that of the earlier model Intoxilyzer 4011AS-A. Four of the five compounds (toluene, the two xylenes, and isopropanol) are registered by this version of the Intoxilyzer as interferences by the instrument at given points in their concentration and one (methanol) is not. From the point of view of where this interference mechanism is triggered, the compounds can be ranked in terms of their probability (if present) of causing an undetected false-positive reading for ethanol in this order: methanol > toluene > the xylene > isopropanol. Effective DUI / DWI DefenseGiguiere, Lewis, and Baselt examined a 52-year-old male cabinet maker with a 20-year history of work-related exposure to lacquers and paint thinners. At 3:36 p.m he received a test reading of 0.369 percent digital, 0.312 percent printout (w/v) on an Intoxilyzer 5000, with the printout indicating “interferent subtracted.” At 3:48 p.m., 0.273 percent digital, 0.245 percent on the printout, also indicating “interferent subtracted.” A blood sample drawn at 3:40 p.m. indicated ethanol 0.0 percent, acetone 0.025 percent (w/v), and toluene 11 mg/L. Although the highest apparent blood alcohol concentration (0.31 % w/v) given by the Intoxilyzer for this subject is 282 times that of the actual blood toluene concentration, because toluene exhibits a blood:breath ratio that is 116 to 300 times less than that of alcohol, and because it demonstrates significant infrared absorption at the 3.50 A 0.06 micron wavelength used by the Intoxilyzer 5000, we consider it likely that toluene caused the instrumental interference observed in this case. Diethyl ether vapor may substantially interfere with breath alcohol analysis by instruments based on infrared absorption at 9.5 um. ... IR analysis for breath-alcohol at 9.5 um ... would not provide a foolproof solution. Common volatile organic compounds other than ethanol, which occur for example, in solvents, perfumes, and food, also contain carbon-oxygen functionality and exhibit IR absorption bands that overlap this wavelength. Included among these are the following: other alcohols, esters, ...and ethers ... Fuel CellThe Alcolmeter device makes use of an electrochemical detector for the determination of ethanol. The alcohol present in a measured volume of breath is oxidized at a platinum electrode surface to generate an electric potential which can be registered. The detector is not specific for ethanol. It gives a response to methanol, n-propanol, isopropanol, and acetaldehyde but is insensitive to acetone. Next article: Index: |
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