Metrological traceability of the breath alcohol measurements

Abstract

Breath alcohol measurements are widely used worldwide to detect the presence of alcohol in the human body. For those measurements, different metrological traceability chains are used, both in the international normative documents and at the national level. Different measurement standards used to calibrate breath analysers reproduce different quantities: on the one hand, an «actual» ethanol mass concentration, and, on the other hand, the operationally defined «ethanol mass concentration by Dubowski (or Harger)». This makes the comparability of the breath alcohol measurements questionable. According to various studies, the discrepancy between the operationally defined quantity and the concentration not related to the empirical interphase distribution coefficients, lays within (1-2) %, although there is also an evidence of a larger deviation. It is possible to construct a common metrological traceability chain by using reference gas mixtures in cylinders and dynamic gas mixture generators based on the principles not related to empirical equations, as well as determining more accurately the interphase distribution coefficient and evaluating its uncertainty. SE «Ukrmetrteststandart» possesses internationally recognised calibration and measurement capabilities for measuring ethanol concentration and producing reference materials: calibration gas mixtures of ethanol with nitrogen or air in cylinders and reference aqueous solutions of ethanol that provide metrological traceability for the breath alcohol measurements.