Development of Control Material for Exhaled Breath-Alcohol Testing and its Application

Breath analyser tests are used worldwide to obtain proof of alcohol intoxication and often used in the conviction of traffic violators. These tests are conducted to quickly and painlessly determine the existing concentration of alcohol in arterial blood by measuring the amount of ethanol in exhaled breath, which can be identified with an electrochemical sensor.At present, the calibration and maintenance of analysers used for these tests are typically performed regularly but lack quality control. Consequently, test results may not be accurate because of calibration deterioration.The aim of this study was to develop and evaluate the uncertainty of control materials used in breath-alcohol testing at the Bangkok Metropolitan Police Station.

Ethyl alcohol (99.99%; Certified Reference Material grade) diluted at three different concentrations was kept under design conditions. The concentrations were 28, 67, and 134 mg/dL, determined by performing headspace gas chromatography, and the uncertainty was set as ±1.3925, ±2.8736, and ±1.8231 mg/dL (±4.97%, ±4.29%, and ±2.72% for the concentrations, respectively), as per ISO Guide 35:2017.

The total error percentages of the developed control materials were 4.97%, 4.29%, and 2.72% for concentrations of 28, 67, and 134 mg/dL, respectively. Each concentration of the materials was tested by using measurements from 70 breath-alcohol analysers belonging to the Bangkok Metropolitan Police Station.

These control materials are applicable to quality assurance and standards tests and may help to ensure the accuracy of breath-alcohol testing in the future.