From The Telegraph (UK):

Sonica Devi, 22, a final year student at Derby University, developed a new method of forensic analysis to help police find tiny traces of drugs.

She put her method, which makes detection of the drug possible even at a million millionth of a gram, to the test on samples taken from telephone boxes across Derby.

The university said she used an ultra sensitive Gas Chromatographic technique which allowed her to find cocaine at picogram levels - one million millionth of a gram - from forensic swabs.

Gas Chromatography linked to a mass spectrometer (GCMS) is an established technique for separating complex mixtures of compounds and detecting them down to very low amounts.

A picogram is one thousand times smaller than a nanogram and a thousand thousandth times smaller than a microgram (a millionth of a gram).

The study, entitled ''Real world detection of cocaine at the picogram (one trillionth of a gram) level in an urban environment'' is now being presented at a number of forensic science conferences across the UK.