Fast, easy, and highly sensitive arsenic detection with gold nanoparticles

Nov 25, 2009

(PhysOrg.com) -- Mention of arsenic poisoning usually brings to mind underhanded murder. However, the danger of arsenic poisoning from contaminated drinking water is far greater. Low concentrations of arsenic are found in nearly all soils and thus also in ground water. About 140 million people worldwide possibly drink water that contains arsenic concentrations above the WHO-recommended limit of 10 ppb (parts per billion).

Researchers at Jackson State University (MS, USA) have now developed a new approach for a rapid, easy, and highly sensitive test. As Paresh Chandra Ray’s team reports in the journal Angewandte Chemie, their method is based on the aggregation of gold nanoparticles, and it selectively detects arsenic in drinking water down to concentrations of 3 ppt (parts per trillion).

Countries like India, Bangladesh, and Thailand are primarily affected by ground water with high arsenic concentrations. However, high concentrations of arsenic have also been found in some areas of North and South America. Once detected, the problem can fairly easily be addressed. Current analytical techniques are time-consuming and require a series of enrichment steps.

The new process could now speed up and simplify arsenic analysis. The scientists working with Ray have attached special organic molecules to the surfaces of gold nanoparticles. These molecules act as “ligands” for arsenic, meaning that they form a complex with it. Each arsenic ion can bind to three ligands, which allows it to link together up to three gold particles. The higher the arsenic concentration in the sample, the more strongly the gold particles clump together and the number of bigger aggregates increases. The color of gold nanoparticles in a liquid depends on their size. Whereas the arsenic-free appear red, arsenic-induced aggregation causes the color to change to blue. Concentrations down to 1 ppb can be detected with the naked eye by means of the color change. Arsenic binds to the ligands much more strongly than other metals; the researchers were able to increase this selectivity by attaching three different ligands to the gold.

One very precise method for detecting minimal changes in particle size is dynamic light scattering (DLS), in which laser light scattered by the particles is analyzed. By using DLS, Ray and his co-workers were able to detect and quantify arsenic concentrations as low as 3 ppt. In samples of well water from Bangladesh, the team found 28 ppb arsenic; in from taps in Jackson (Mississippi, USA) they found 380 ppt.

More information: Paresh Chandra Ray, Use of Nanoparticles in a Simple Colorimetric and Ultrasensitive Dynamic Light Scattering Assay: Selective Detection of Arsenic in Groundwater, Angewandte Chemie International Edition 2009, 48, No. 51, 9668-9671, doi: 10.1002/anie.200903958

Provided by Wiley (news : web)

Explore further: Graphene reinvents the future

add to favorites email to friend print save as pdf

Related Stories

Water-stingy agriculture reduces arsenic in rice markedly

Jul 28, 2008

A new farming method first developed to conserve precious irrigation water may have the added benefit of producing rice containing much less arsenic than rice grown using traditional rice-farming methods, researchers in the ...

Study: Crystal removes arsenic cheaply

Nov 10, 2006

A common rust-like crystal may offer an inexpensive way to rid drinking water of hazardous levels of arsenic, Rice University researchers in Houston said.

Arsenic exposure could increase diabetes risk

Aug 19, 2008

Inorganic arsenic, commonly found in ground water in certain areas, may increase the risk of developing type 2 diabetes, according to a study by researchers at the Johns Hopkins Bloomberg School of Public Health. The study ...

Recommended for you

Graphene reinvents the future

Aug 27, 2014

For many scientists, the discovery of one-atom-thick sheets of graphene is hugely significant, something with the potential to affect just about every aspect of human activity and endeavour.

Catalytic gold nanoclusters promise rich chemical yields

Aug 25, 2014

(Phys.org) —Old thinking was that gold, while good for jewelry, was not of much use for chemists because it is relatively nonreactive. That changed a decade ago when scientists hit a rich vein of discoveries ...

Copper shines as flexible conductor

Aug 22, 2014

Bend them, stretch them, twist them, fold them: modern materials that are light, flexible and highly conductive have extraordinary technological potential, whether as artificial skin or electronic paper.

User comments : 0