The social awareness of the problem of drunk driving has increased greatly over
ID: 511000 • Letter: T
Question
The social awareness of the problem of drunk driving has increased greatly over the last 25 years. One of the tools that has helped law enforcement agencies keep the general public safe is the portable Breathalyzer, which uses an electrochemical reaction to analyze the amount of alcohol in the breath of a user.
What is a reaction utilized by these devices? There are a few different methods these devices use to find a BAC, so if you find multiple reactions, just choose one. How does the device translate the result of the reaction into a BAC value?
what can you think of as a complicating environmental factor? What effect would it have on the instrument readings?
Explanation / Answer
The basic principle involved in breathalyzer is oxidation of ethyl alcohol into acetic acid.
At anode:
C2H5OH + H2O ----> CH3COOH + 4H+ + 4e-
At cathode:
O2+ 4H+ + 4e- ----> 2H2O
Overall reaction:
C2H5OH + H2O+ O2 ----> CH3COOH + 2H2O
From anode to cathode there is a flow of electrons. Generally produce current. The current produced by the chemical reaction is measured by a microprocessor and display as an approximation of overall blood alcohol content (BAC) by the alcosensor.
If the environment contains gasoline, fluids like ether , alcohols and some other volatile compounds in air as pollutants effects the BAC values. When a person exposed to those pollutants containg air eventhough the person is not an alcoholic but the breathalyzer gives the positive results. And finally gives false BAC values. Because all the above pollutants are easily oxidisable substances lok ethyl alcohol and gives false BAC values.
Such type of false BAC values are given by breathalyzer because of pollutants in the environment.
Example: Methyl tertiary butyl ether if present in the environment gives positive values of BAC. Eventhough the person is not alcoholic.