Breathalysers Flashcards
How do fuel cell breathalysers work?
Platinum oxidises any alcohol to ethanoic acid, h+ ions and electrons.
External circuit is attached to both platinum electrodes and also a current meter.
H+ ions move through fuel cell and combine with oxygen to produce h2o.
More ethanol oxidised the larger the current.
Microprocessor measures the current and calculates BAC.
Construct of a dichromate (vi) breathalyser?
Ethanol is oxidised to ethanoic acid Orange potassium dichromate (vi) is reduced to green chromium (III).
Second tube is used for comparison.
Colour change is detected by a meter and an electric current causes the needle to move from resting.
How do IR breathalysers work?
IR radiation is passed through the sample and certain wavelengths are absorbed.
The spectrum allows the concentration of ethanol to be deduced.
Gives accurate results.
Less portable.
Problems with breath analysers
Must be calibrated regularly.
Alcohol can come from tongue mouth or stomach but the breath is only a composition of deep in the lungs.
Can’t be used in court, too many errors.
Operator gives 15-20 minutes before along further readings
