On the Trail of Doping Offenders - Mass spectrometry in vacuum detects illegal substances

On the Trail of Doping Offenders - Mass spectrometry in vacuum detects illegal substances

Doping is widespread in the upper echelons of various sports, but it is difficult to prove. Detecting performance-enhancing agents in blood and urine samples requires complex trace analysis. Vacuum pumps are an essential part of the technology.

When Ben Johnson sprinted to victory over 100 meters in a time of 9.79 seconds at the 1988 Olympic Games in Seoul, the Canadian not only won a gold medal. He also set a new world record and finally defeated his archrival, US sprinter Carl Lewis. Barely 68 hours later Johnson had to return his medal. He had doped, and the anabolic steroid stanozolol was detected in his urine.

Constant search for the unknown

The case of Ben Johnson is only one of many doping cases in upper-level sports. Then, as now, athletes are under enormous pressure to perform, and forbidden performance-enhancing substances are considered by some as a proven means to success. Detecting these substances in blood and urine samples is a challenge, despite regular checks and high-tech analysis. Many are metabolized quickly, and the time span in which they can be detected is short. What is more, new drugs or variants of already known substances are constantly coming onto the market. The seven-time Tour de France winner Lance Armstrong, for example, escaped the testers for years.

Finest analytics in vacuum

In the search for suspicious substances, laboratories certified by the World Anti-Doping Agency (WADA) rely primarily on a combination of gas chromatography and mass spectrometry. Using vacuum, this technology can detect even tiny traces of a few picograms or femtograms per milliliter of urine.

Extracts from the samples are first evaporated in a high vacuum and separated into individual substances in the gas chromatograph. They are then passed one after the other into the mass spectrometer, which sorts them according to mass and charge. The unknown compounds are ionized first, most often by electron impact ionization. Some of the molecules disintegrate into charged fragments. The resulting ions are now accelerated, pass through an electric and magnetic field and finally hit the detector.

The whole process takes place in a high vacuum so that the ions are not scattered by the collision with air molecules and deflected from their path to the detector. Vacuum systems ensure a constant negative pressure of one millionth of a millibar at the most during the analyses.

As soon as the detector registers signals, spectra corresponding to the specific mass of the molecules and fragments are recorded. Special software and databases are used to help with interpretation. This allows conclusions about the substances contained in the sample to be drawn from the different peak values and the concentration of these substances to be calculated. It is then possible to use this to derive whether a limit value has been exceeded.

There are two reasons why urine samples are so important. First, most prohibited substances used by athletes are excreted by the kidneys, which is why they are present in relatively high concentrations in urine samples. This makes it easier to detect, as even state-of-the-art analytical instruments with the highest resolution can only determine quantities of substances up to a certain lower threshold.

Furthermore, many doping substances can be detected longer in urine than in blood. Some substances disappear from the blood after one day, but can still be detected in the urine seven to ten days later. The intake of anabolic steroids can now be detected for as long as four weeks after discontinuing ingestion. Blood tests are mainly performed to check whether an athlete has manipulated the oxygen transport capacity of his/her blood through transfusions or growth factors such as EPO (erythropoietin).

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