Evaluation of a portable evidential breath alcohol analyzer

Abstract 

The Scientific Laboratory Division (SLD) of the Department of Health acts by mandate as the regulatory agency for the Implied Consent Program for the State of New Mexico. The Laboratory is responsible for all blood and breath alcohol testing activities for law enforcement statewide. The geographical size and the nature of the state, characterized by a highly rural population, demands portable breath alcohol testing equipment. Moreover, future expansion and success of the breath-testing program has focused on instrument portability and data management as critical issues amongst law enforcement agencies and the courts. Thus, the Implied Consent Section of the SLD evaluated the performance of the Intoxilyzer^® 8000, a portable instrument, against the Intoxilyzer^® 5000, a stationary instrument, which is currently approved for use.

Instrument performance was evaluated at various ethanol concentrations, ranging from 0.04 to 0.55g/100mL in blood or g/210L breath. Special attention was placed on instrument performance at the per se and aggravated DWI levels of 0.08g/100mL and 0.16g/dL, respectively, due to their legal significance. Precision and accuracy were evaluated using in-house ethanol controls in a wet bath simulator. Coefficients of variation using the Intoxilyzer^® 8000 ranged from 0.30 to 1.3% (n=102), while CVs for the Intoxilyzer^® 5000 were 0.7–2.1% (n=102). Calibration stability was assessed in addition to the distribution of data at concentrations between 0.04 and 0.55g/210L. Accuracy was 100–102% for the Intoxilyzer^® 5000 and 99–101% using the Intoxilyzer^® 8000. Linear regression analysis of more than 700 comparative measurements revealed an R² of 1.000 (y=1.005x–0.001), where the Intoxilyzer^® 5000 and the Intoxilyzer^® 8000 were plotted on the x- and y-axis respectively. Instrument response to mouth alcohol and volatile interferences was also investigated. Potential interferences were evaluated alone or in combination with ethanol using a wet bath simulator at 34.0°C.

The effects of extreme temperature and altitude were also examined using wet bath simulators and dry gas calibrant. Accuracy and precision were evaluated at high and low temperatures. High altitude performance was evaluated at 3534 m above sea level at a local ski resort. In addition to the scientific study, field evaluations were also conducted by law enforcement personnel. Based upon the results of the study, the Intoxilyzer^® 8000 was approved as an evidential breath alcohol analyzer in the State of New Mexico.

Keywords: Ethanol, Breath, Validation