According to the U.S. Department of Justice, around 200,000 women were raped in the U.S. in 2007 with the aid of a "date rape" drug - and because so many cases go unreported, the actual figure is believed to be 80 to 100 percent higher. GHB is one of the most commonly used drugs because it is odorless, tasteless and invisible when dissolved in water. Now researchers at Tel Aviv University's Sackler Faculty of Exact Sciences have developed an easy-to-use sensor that, when dipped into a cocktail, can instantly detect GHB and another commonly used date rape drug, ketamine.

The researchers say that real time date rape drug detection has been impossible until now because of the lack of a sensor sensitive enough to detect the drugs. Adding to the difficulty of proving the presence of such drugs is that after a few hours they become undetectable in the human bloodstream. With rates of drug-assisted sexual assault a growing problem around the world, the TAU researchers set about developing a sensor that was lightweight, discreet and could be carried in a pocket or purse.

The system they developed works on simple optics principles, says Professor Fernando Patolsky. Although date rape drugs are colorless and odorless when mixed into a cocktail, they do subtly change the optical properties of the drink and it is this change that the new sensor detects. When a ray of light comes into contact with a drugged drink, a "signal change" occurs and the sensor sounds an alarm. A commercial version of the sensor could emit a beeping noise or a small flashing light for use in the dark and loud environment of a bar or club.

Tests conducted showed the sensor detected both GHB and ketamine with 100 percent accuracy and no false positives. Prof. Patolsky says that just one to ten microliters is required for the sensor to detect the drugs.

The TAU team is currently working to miniaturize the system so it is easy and affordable for personal use. Although GHB and ketamine are the two most commonly used date rape drugs, the researchers are also looking to widen the range of drugs that the sensor can identify.

When the sensor becomes commercially available, Prof Patolsky says it might look like a pen or clip that is easy to dip into a glass. A disposable cartridge inside that is responsible for recognizing the presence of a drug would cost less than a dollar and be able to identify two or three spiked drinks before needing to be replaced.

All elements of the system have been patented with TAU's technology transfer company, Ramot, so - unfortunate as it may be - it might not be too long before the sensor is an essential inclusion in any woman's purse on a night out.