Drug Detection
When substances such as diuretics and steroids are tested for, it is not the pure substance that is detected but their metabolites. All drugs go through a process of bio-chemical reactions in the body. When the active compound in the drug is released during the reactions, the drug's structure slightly changes. These altered structures are called metabolites and are excreted from the body. It is these metabolites that are detected in drug tests. Laboratories use several methods to detect the presence of drugs or their metabolites. When drug metabolites are circulated in the blood, they enter several blood vessels. Any metabolites present will be filtered through the hair, which forms the basis of hair testing. Metabolites present in the hair are a permanent record of drug use. Although very expensive, testing is an extremely accurate of checking for drug use. However, it is not very common and there are slight dangers of infection. Saliva testing is also used, however it too is not very common as it can only detect recently used toxins (maximum 3-4 days prior).
Urine Sampling
The most popular form of testing is urine sampling as it is cost effective, very accurate and there is no danger of infection. Urine tests are best taken in the morning when the presence of drugs is most concentrated. As soon as the sample is obtained, volume, pH and sometimes specific gravity and temperature of the sample are measured. These can identify some methods of cheating the drug tests such as the use of vials of urine or tampering with the actual sample. The pH (how basic or acidic it is) of urine can affect the analysis of some drugs and their metabolites. Some athletes have been known to orally administer basic substances, such as sodium bicarbonate, to change the urine's pH. The specific gravity is a method of checking if the concentration of drugs has been diluted, such as the use of diuretics.
Once a sample is taken from an athlete, it is sent to a laboratory for analysis. On an annual basis, over 100,000 drug tests are conducted worldwide at a cost of over $30 million. An area of chemistry known as toxicology is used to test the samples for banned substances. In toxicology, substances are qualitatively and quantitatively analyzed in body fluids to identify drugs and other toxins. Laboratories use several techniques to do this, which include immunoassays, gas chromatography, mass spectrometry and thin-layer chromatography.
Immunoassay
A method called immunoassay is usually used to screen samples. Every drug (antigen) has an antibody that will bind to it only. The sample is mixed with a solution containing an antibody, which is usually tagged with a fluorescent dye or radioactive substance. The amount of fluorescence or radioactivity is measured and thus the concentration of the tested substances can be found. Immunoassay is used to identify banned peptide hormones.
Unfortunately, immunoassay is deemed to be insufficient so more accurate methods are needed. The most popular methods of chemical analysis are gas chromatography and mass spectrometry (GC-MS).
Gas Chromatography
In gas chromatography, the sample is heated to convert it to gas, which is then passed through a long machine. The vaporized sample is collected in columns, which isolates the drug metabolites in the samples. As the conversion rate from solid/liquid to gas is different in various substances, the gas samples are collected at different intervals and therefore isolated. The collected gas samples are then transferred to the mass spectrometer.
Mass Spectrometry
In mass spectrometry, the sample is bombarded with electrons, which charges the sample. After a series of stages the different substances in the sample are separated. Every compound has a characteristic weight and charge and so any drug metabolites can be identified from these properties. The gas chromatography-mass spectroscopy method allows for the detection of anabolic steroids, diuretics and stimulants at the part per million level, even when it is present in a complicated matrix structured substance as urine.
Thin layer chromatography
Another method called thin layer chromatography is used to indicate the presence of drugs. The sample is dissolved in a substance, which cause drug metabolites to travel up a strip at different rates while leaving colored spots behind. Each substance travels a different distance, so the strip can be compared to standard distances.
Other Methods
New tests currently under development include one that examines the size of red blood cells. If the size and iron content of the sample is outside a certain range, drug usage can be recognized.