Kolkata, Feb 24 (IANS): Scientists in Kolkata have developed a new high-precision technique to detect arsenic in water, a toxic substance widespread in the groundwater of India and Bangladesh that on long-term exposure is capable of causing skin cancer.

According to the WHO, natural arsenic contamination is a cause for concern in many countries, including Argentina, Bangladesh, Chile, China, India, Mexico, Thailand and the US.

The new method developed by the scientists enables high-precision detection of arsenic through tiny gold clusters that signal its presence in water by emitting light (a phenomenon called fluorescence).

"The ultra-sensitive sensors synthesised by us were in the form of gold clusters that signal the presence of arsenic in water by emitting more light or fluorescence when in contact with the toxic arsenic in water.

"It even detected arsenic in presence of other toxic metal ions," Arindam Banerjee of the Department of Biological Chemistry of the Indian Association for the Cultivation of Science, told IANS.

Chandra Bhushan, deputy director general of the Centre for Science and Environment, New Delhi, said arsenic poisoning in India is a widespread phenomenon which needs monitoring techniques as well as methods for removal of the toxic substance.

"Arsenic poisoning of groundwater is widespread in Uttar Pradesh, Bihar and West Bengal. Even our neighbour Bangladesh faces the same problem.

"Scientific studies in monitoring techniques as well as methods to remove the arsenic from water are necessary," Chandra Bhushan told IANS.

The unique feature of the new monitoring technique is that it can roughly indicate the extent of arsenic contamination.

"The more the light emitted, the greater the quantity of arsenic present," Banerjee added.

The gold clusters of sub-nano dimensions were capped with a small peptide (a dipeptide) to stabilise the entire structure.

"The dipeptide, i.e., two residue containing small peptide (dicysteine), was used to stabilize the fluorescent gold clusters. The nascently prepared gold clusters have a natural tendency to aggregate to form bigger sized particles; that is why you need to have capping or stabilising agent to prevent aggregation.

"The nascently formed gold clusters and peptide are biocompatible, innocuous agent to the environment," Banerjee explained.

Unlike other sensors, these gold clusters are particularly sensitive for detection of arsenic in water that contains other metal contaminants as well.

"The fluorescence intensity of the gold cluster almost remains same in the presence of different metal ions such as magnesium, manganese, iron and zinc. In fact, these clusters are so sensitive and precise that they can detect or sense arsenic ions in water even if they are diluted to 40 times their original concentration," Banerjee added.