Alcograd works on the principle of ethyl alcohol (ethanol) in the blood partitioning with the air in the lungs, which causes it to escape via exhaled breath.
The method of detection employs potassium dichromate crystals, which are maintained in a fresh environment, within a sealed ampoule until the test is administered. When the crystals come into contact with ethyl alcohol they cause the ethanol to be oxidised into acetic acid (vinegar), according to the equations below. When this occurs, the crystals loose oxygen atoms and undergo a corresponding colour change, which is used as an indicator to identify the presence of alcohol.
(i) Cr2O72- + 3C2H5OH + 8H+ → 2Cr3+ + 3CH3CHO + 7H2O
(ii) 2Cr2O72- + 3C2H5OH + 16H+ → 4Cr3+ + 3CH3COOH + 11H2O
Each Alcograd test kit contains of the following inclusions:
Sealed test tube
The following instructions provide details on how to use Alcograd to determine the blood alcohol level of a test subject.
Wait for at least 20 minutes after the last alcoholic drink and 5 minutes after the last cigarette.
Press both ends of the tube to break the aluminium seal.
Use the test immediately following activation.
The subject should take a deep breath and blow in one continuous breath through the end of the tube designated by the arrows.
Ensure that no inhalation takes place.
After 2 minutes identify any colour change amongst a majority of the crystals.
Most of the crystals remain clear in colour. This indicates that the breath alcohol is approximately 0 %.
In the instance of a positive test, where the level of alcohol detected in the breath corresponds to a blood alcohol level of > 0.02 %, crystals within the tube will the colour corresponding to the BAC as marked on the tube.
Note: For best results it is recommended that comparison with an unused test be made, in order to establish if a colour change has occurred.
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