Virginia's new DWI detection device

On April 23, 2008 Virginia started listing the Intox EC/IR II as an approved device according to the Breath Alcohol Testing regulations. Virginia signed a contract with Intoximeter to purchase 220 devices that same day.

Alka Lohmann is the chief of Virginia's unaccredited breath alcohol section. At the May 5, 2008 Scientific Advisory Committee meeting, Ms. Lohmann gave a status report on the EC/IR II. She reported that out of 50 states this tester is used in only four states besides Virginia: West Virginia, Wisconsin, North Carolina and Tennessee. Ms. Lohmann did not indicate why only 10% of the states used the EC/IR II. She stated that the new tester offered enhanced communication capabilities, increased trouble shooting form the lab and the ability to use a dry gas.

Ms. Lohmann was asked about the types of reports that can be requested related to the device. She stated that the same reports presently available will be available for the new machine.

One of the basic principles of analytical chemistry is the each analysis such be corroborated by an independent, alternative method. Agreement between the two different analytical methods insures the reliability of the results.

The name EC/IR II implies that the machine will measure the subject's alcohol concentration in two methods: EC means electrochemical or fuel cell while IR means infrared. By this method, the device guarantees the reliability of its results through using different tests. This internal corroboration would give the EC/IR II a distinct reliability advantage over devices utilizing only one technology.

Unfortunately, Intoximeter was unable to coordinate the different analytical methods. Because of that failure, the instrument does not use two independent methods to measure alcohol concentration. Instead, the EC/IR II uses only the fuel cell to measure alcohol and determine blood alcohol content. The infrared is used to monitor breath sample quality and to detect mouth alcohol.

The fuel cell component does not have the ability to detect mouth alcohol. The fuel cell merely measures total concentration of alcohol present whether from lung air or mouth.

Over time, fuel cells change in sensitivity and must be calibrated frequently to retain accuracy. IR detectors do not require calibration every few weeks. As the electrode microstructure changes over time the sensor baseline drifts. That drift takes the EC out of sych with the IR detector.

Calibrating the device every few weeks would be very demanding and time consuming. Some states have resolved that issue by disabling the IR detector entirely. Once the IR detector is disabled the device has no capacity for detecting mouth alcohol.

Copyright (c) 2008 Robert Keefer

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