Of the average of 4,000 samples processed each year by this lab, around 20 per cent are deemed worthy of further investigation and 1 per cent yield positive results.
The actual figure for positive tests across all sports domestically has fallen slightly over the last three years. In 1992-93 there were 48; in 1993-94, there were 41.
'These figures are reflected in the 90,000 tests that are conducted annually, worldwide across all sports,' said Dr David Cowan, who is the director of the Drug Control and Teaching Centre.
'I see it as a victory rather than a defeat,' he said. 'In sports where there is a testing programme, fewer people are taking drugs.'
Once a urine sample is taken from a competitor, the container, with a number etched into it, is sealed and delivered to the laboratory - preferably within three days. It is then divided, with half - the B sample - being frozen and stored for possible future use as a check.
Cowan recalled an occasion when a batch of samples from Ireland were held up at customs in Liverpool and arrived at the lab a month late. They were not fit to be tested. But once a sample is frozen it should not degenerate. 'We tested one sample satisfactorily a year after it had come in to us,' Cowan said.
The part of the sample which goes forward to immediate analysis - the A sample - is split again into several components before undergoing a process of increasingly thorough screening.
A portion tested for the presence of banned stimulants is put through a gas chromatograph, which resembles a small oven. Here it is processed through a silicon tube at temperatures of up to 270C. Heating and gas flow are constant, and as the sample breaks up, its components take differing times to be detected at the end of the tube - known as reduction times.
These times are known. With ethedrine, for instance, the relative pointers are 2.8 and 3.1 minutes. Its proportion within the overall sample can be measured at the same time.
Testing for drugs in the steroid class - generally present in far smaller quantities than stimulants - involves a similar process of gas chromatography and also employs a mass spectrometer, which can provide a more detailed profile.
In every case, the first testing of the A sample represents a screening process. If the presence of a banned substance is suspected, another part of the A sample is tested as a check. Often it can be treated in a way which makes it easier to confirm the suspect chemical involved.
Of course, the battle of wits between the testers and those attempting to remain one step ahead goes on. But there was some encouraging news from the front yesterday from Dr Cowan, who reported that researchers were about to finalise a test for dihydro testosterone and human chorionic gonadotrophin, naturally occurring substances which are taken artificially to improve athletes' stamina and endurance.
'I think we are making some impact,' Cowan said. 'I used the analogy of drilling metal. We are going three forward, two backward. But overall we are advancing.'
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