A new sensor which can tell if a drink has been spiked with a date rape drug has been developed by a research team from the National University of Singapore (NUS).

The liquid sensor changes colour when it detects the presence of the drug known as gammahydroxybutyric acid, or GHB. When mixed in a beverage that contains a concentration of GHB enough to "affect consciousness" - typically about 1 gram in 100ml - the sensor's fluorescent orange colour will fade visibly. It works in water, red wine, vodka and even cocktails like the Singapore Sling.

As the sensor cannot be ingested, a sample, which can be as little as a drop, must be taken from the drink for testing. GHB acts as a relaxant that can reduce inhibitions and even induce a coma-like sleep if taken in large amounts.

The research team, led by Professor Chang Young-Tae of NUS' Department of Chemistry, hopes that the sensor will be able to reduce instances of sexual assault of victims under the influence of GHB.

Currently still being fine-tuned, the sensor works best when viewed under ultra-violet or green light as the colour change will be most apparent.

The final form of the product has also not been finalised, but Prof Chang said that the team is working with industry partners to "develop a handy and cheap device for GHB detection". Such a device could, he said, take the form of a stirrer that contains the liquid sensor within a smaller vial. It could also take the shape of a larger device which can be connected to a mobile phone for a reading.

Prof Chang estimated the device should be available in the market within the next year.