Drug testing is an unfortunate fact of life. It is most commonly used for testing athletes, job applicants, and when there is trouble with the law. The following information outlines how drug tests actually work from a technical point of view.
The most common form of test is the screening test. This method uses antibodies much in the same way our immune systems do to identify and latch onto certain substances. Antibodies are made from 4 protein chains that create a “Y” shape. The end of the arms of the Y vary in shape from antibody to antibody. The idea is that when a white blood cell comes across a foreign object within the body, the antibodies with the cells try and latch onto it with their varying shapes. If the shape is correct, it will latch on and the white blood cell will produce many more of the same shaped antibody to swarm and neutralise the foreign entity.
Antibodies are used in the same ways by scientists to detect drugs. When a scientist has an antibody specific to what they are looking for, they can perform an ELISA test. This basically involves attaching the antibodies to the bottom of a special plate and washing the sample in question over it. After a while, if any of the drugs being looked for are present, they will latched onto by the antibodies and held in place.
Next the plate is washed to remove the remaining excess material, leaving everything of interest behind. More anti bodies are then added, ensuring that the substance being looked for is completely surrounded. Once this is the case, a secondary antibody is added that is a lot more general in nature. This more general antibody will have been engineered to have an enzyme that produces colour in it, as well as to latch onto the other, primary antibodies already present.
Lastly, a substance that changes colour in the presence of the enzyme held within the secondary antibody is added. If the substance changes colour, it indicates to the scientists that the drugs they were looking for have been captured by the antibodies within the sample.
The confirmation test is a much more advanced and expensive way of testing for drugs. It is usually done with one of two methods. These are gas chromatography and mass spectrometry.
Gas chromatography forces the components within the sample to separate, making them easily identifiable by passing them through a narrow column with inert gas at a high pressure.
Mass spectrometry is a method that bombards the molecules of the sample with electrons, forcing it to break up. Each molecule has a specific way it breaks, effectively causing it to have a unique identifier or “fingerprint”. This allows scientists to identify drugs as they break apart.