- 22 November 2006 -

Test can detect small amounts of water in parts per million

A new method for the detection and measurement of small amounts of water in as fuels, lubricants, or organic solvents has been developed in the organic chemistry department of the Weizmann Institute, based in Rehovot, Israel. It consists of a versatile film on glass that is only 1.7 nm thick. The film can measure the number of water molecules in a substance even when it contains only a few parts per million.

The method is said to be a departure from previous sensing techniques that are usually based on relatively weak but selective 'host-guest" interactions. In the Weizmann Institute team's sensor, metal complexes embedded in the film steal electrons from the water molecules. When the number of electrons in the metal complexes changes, so does their colour, and this change can be read optically.

The test can be done quickly, and the molecular film can be returned to its original state by washing it with a simple chemical. The film also remains stable, even at high temperatures and with repeated use. In addition, it can be deposited in an inexpensive, one-molecule-thick layer on glass, silicon, optical fibre or plastic. The ease and low cost of fabrication may also make such films suitable for one-time use, the Institute says. The scientists are now exploring the possibility of adapting the method to testing for trace amounts of materials or substances such as specific metal ions or gasses.

www.weizmann.ac.il