D.4.3 Describe and explain the techniques used for the detection of ethanol in the breath, the blood and urine.

Alcohol Breathing Test:

Breathalyser: Potassium Dichromate (VI)


In the reaction above,
  • The Sulfuric Acid is used to create a liquid solution containing the ethyl alcohol from the breath, which was originally in gaseous state
  • The Potassium Dichromate (reddish-orange) is used to react with the Ethyl Alcohol , which results in the production of Chromium Sulfate (green), Potassium Sulfate, Acetic Acid, and Water
  • The Silver Nitrate is used as a catalyst
  • The shade of green of the Chromium Sulfate indicates the amount of Ethyl Alcohol in the reaction
  • In order to determine the amount of Ethyl Alcohol in the reaction, the solution resulting from this reaction is compared to the original non-reacted solution in a photocell system
  • The photocell system sends a current through the solutions, which moves a needle on a display, and the concentration of Ethyl Alcohol is shown through how much the operator has to turn a dial to move the needle back to its resting point
  • A breathalyzer test CANNOT determine the blood alcohol concentration of an individual, only a blood alcohol test can. The breath alcohol concentration is generally used in order to estimate the blood alcohol concentration of an individual

Intoximeter: Absorption of Infrared Radiation

The use of infrared to detect ethanol in a person's breath is based on the
fact that certain infrared wavelengths can be absorbed by ethyl alcohol (ethanol) molecules


Part A The Infrared Radiation is generated, usually from a quartz lamp.
Part B The person breathes into this part
Part C Where the breath comes out
Part D The sample chamber, where the breath is stored.
Parts E The lenses that focus the IR beam from the lamp.
Part F The filter wheel, it filters out everything but specific wavelengths of the bonds in ethanol.
Part G A photocell, which converts those wavelengths into an electric pulse.
Part H The microprocessor, which interprets the electric pulse and calculates the Blood Alcohol Concentration based on the change in bond lengths in the ethanol.

Intoximeter: Fuel-Cell

By oxidizing ethanol, you get acetic acid, and two hydrogen atoms (two protons, and two electrons)
The devices using the fuel cell technology to detect alcohol have two platinum electrodes, and a electrolyte material in between.
The protons then move across the electrolyte, while the electrons move through wires connected to the platinum plates. On the other side, the protons and electrons bond with oxygen to form water. The current across the wire is measured, and sent to a microprocessor, which calculates the BAC.

external image breathalyzer%20I.jpg

Alcohol Urine Test:

Detecting Alcohol Level in Urine

- When alcohol is consumed, it travels through your body and through the small intestine.
- Depending on one's metabolic rate the time it reaches the urine after comsumption varies.
- Alcohol urine testing is RELIABLE because, this test can show presence of alcohol in body for 2 to 3 hours more than the Blood Alcohol Test can.
- It cannot
show the exact degree of alcohol consumption.
- It will only show results up to 5 days after alcohol consumption.
- Many factors influence the level of alcohol in ones blood; a persons metabolism, and dehydration level.
- Collected through means of a plastic container.
- Usually one sample is taken, but sometimes two samples, a primary and secondary sample, are taken for consistency.

Method (Chromatography)
-The client is asked for urine specimen, and then the alcohol is detected by its metabolite Ethyl glucuronide (EtG), (so the presence of EtG shows that there was alcohol consumption).

  • immunoassay (EIA or ELISA)
  • gas chromatography/mass spectrometry (GC/MS
  • liquid chromatography/mass spectrometry (LC/MS)
  • liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS)
The cut off is 100 nanograms per millimeter of EtG, which means definitive alcohol consumption.
( http://www.expertdrugtesting.com/content/view/32/1/)

Alcohol Blood Test:
  • Blood Alcohol Concentration (BAC) is measured in percentage by mass or mass per volume. (E.g. 0.20% BAC means 1 gram of alcohol per 500 grams of blood)
  • An alcohol blood test measures the amount of alcohol (ethanol) in a person's body.
  • Alcohol is absorbed into the bloodstream very quickly and can therefore be detected within minutes of drinking.
  • A blood alcohol test is used to find out if a person is legally drunk or wasted.
  • It is done by a health professional drawing blood which is then analyzed in a laboratory.