A New Methodfor the Rapid A nalysis of Ethanol in Breath, Blood, Urine and Saliva Using the A Icolmeter Evidential Instrument

The introduction of legislation to control driving under the influence o f alcohol has led to the development and use of a number of instrumental methods for measuring the concen­ tration of alcohol in body fluids.11 Standard methods for blood and urine analysis, based mainly on gas chromatography, are in common use and under laboratory conditions can give results with standard deviations of better than 2 mg%. Because of the well established equilibrium of alcohol between pulmonary blood and alveolar air, it is now common practice to measure the alcohol concentration in expired breath and to use the partition ratio to quote the blood alcohol concentration. The obvious advan­ tages and convenience of analysing breath rather than blood have resulted in the development of a number of instruments especially for breath alcohol analysis. Earlier instruments, such as the ‘Breathalyser’ and the ‘Photo-Electric Intoximeter’, were based on the wet chemical oxidation o f the alcohol in a breath sample by a potassium dichrom ate/sulphuric acid mixture contained in a glass ampoule. The later development of more sensitive instrumentation, based on physical methods such as gas chrom atography,12 infrared spectroscopy3 and electrochemical oxidation89 has made possible the better control of the discard breath volume, although in some instances the resistance to blowing still remains too high. A detailed study by Jones et a/ on the factors affecting the accuracy of breath measurements has shown that the ideal breath sampling system should have very little resist­ ance to blowing and that it is desirable to discard at least 75% of the vital capacity.7 14 But, while satisfactory for laboratory use, the cost and mode of operation o f some instruments based on physical methods often renders them unsuitable for routine use in the police station. Factors such as these have been considered in the development of the ‘Alcolmeter’10 and ‘Alcosensor’4 range of instruments based on a fuel cell detector.13 Although the ‘Alcol­ meter’ instruments were originally designed solely for breath analysis, the sampling system can be adapted to analyse the headspace vapours above any fluid containing alcohol, such as blood or saliva, so measuring the fluid alcohol concentration. This communication reports on the precision and accuracy of the ‘Alcolmeter’ instruments in measuring the blood alcohol concentration by means of the analysis of a) expired breath, b) headspace vapour above blood and c) headspace vapour above saliva.