Breath Alcohol Analysis by Standardization to Water Vapour Enables Contact Free Sampling with Preserved High Accuracy and Precision As Compared With Mouthpiece Sampling
Journal Title: Journal of Forensic Investigation - Year 2014, Vol 2, Issue 1
Abstract
A novel breath analyzer has been developed that determines the breath alcohol concentration (BrAC) by tandardizing the exhaled alcohol and water vapour concentrations to the fully saturated water vapour concentration at 37 ºC (44 mg/L). The method enables the determination of a person’s BrAC without the use of a mouthpiece, i.e. contact free sampling. This, however, requires that the amount of breath sample dilution with ambient air is correctly determined. The main purpose of the study was to evaluate the impact of ambient air dilution on the analytical performance of the analyzer. Instrument performance was evaluated at vapour-alcohol concentrations ranging from 0.030 to 2.000 mg/L using a prototype simulator mimicking natural exhalations. The simulator outlet was either connected to the inlet of the analyzer (mouthpiece simulation) or placed at a distance of 50 and 100 mm (contact free simulation). The accuracy was > 98 % and the precision (coefficient of variation, CV) was < 0.3 % in the mouthpiece simulations at concentrations above 0.1 mg/L. In the contact free simulations from 50 and 100 mm the corresponding accuracy was > 98 and 97 % and the CVs were < 0.7 and 1 %, respectively (n = 90). A human drinking study was also performed where seven subjects drank 0.5 g alcohol/kg bodyweight, then providing 168 mouth piece and contact free samples from a distance of 50 and 100 mm. There was no difference between the BrACs of samples from 50 mm and the mouthpiece samples (mean 0.239 mg/L). The BrACs of samples from 100 mm were negligibly lower (0.234 mg/L). Breath alcohol analysis by standardization to water vapour enables contact free sampling with preserved high accuracy and precision as compared with mouthpiece sampling.
Authors and Affiliations
David Grubb
Keywords
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- EP ID EP202473
- DOI 10.13188/2330-0396.1000009
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