Can gold assist in the global arsenic problem?: Insights from speciation and development of an on-site system

Arsenic has been well known for its acute toxicity since the Middle Ages when poisoning occurred frequently. More recently, the debate around the death of Napoleon was a stark reminder of the harmful effect of this metalloid. Unfortunately, today, arsenic is not known for its acute toxicity but rather for its insidious chronic toxicity. In every continent, health problems related to arsenic are encountered. Absorbing high levels of arsenic during several years results in various cancers such as lung, bladder or skin cancer. The most recent and potentially catastrophic example of an on-going arsenic poisoning occurred in the 1970's, when millions of wells were drilled in Bangladesh and India to provide clean drinking water for the people. However, through dissolution processes of the arsenic naturally present in the bedrocks, millions of people are drinking contaminated water. This has been quoted as the biggest poisoning in human kind .Arsenic is present everywhere e.g. in food, water, soils, cigarettes or crops. The assessment of the toxicity of a sample is however difficult. Indeed, arsenic is found in the environment with four different valence states. Each of these can form complexes through association with other molecules and each of these complexes behaves differently in the environment: in terms of mobility, bioavailability (can they be absorbed with living organisms?) and toxicity. In order to be able to understand the toxicity of a sample, to predict the contamination of an area or to apply efficient technologies for the removal of arsenic in a contaminated site, we need to know what arseno species are present in this particular environment. There are different techniques currently used to perform such analysis. However, these techniques are all laboratory-based, generally very expensive and require a skilled operator. In addition, they cost both time and money: sampling, transport, storage and treatment of the sample have to be done before the measurement is finally achieved. Thus there is an incompatibility between the high demand on the number of samples to be analysed, especially in under-developed countries and the limited capacity of the few available (or affordable) measuring systems. The developments of cheap reliable systems that can be used on-site with a high spatial resolution are urgently needed to identify the contaminated sites and thus prevent potential intoxication.Very recently, in the group of Pr. van den Berg at the University of Liverpool, we developed a simple voltammetric method for the determination of the two main species of arsenic that are found in the majority of waters: arsenite and arsenate. The method was tested in marine samples of Liverpool Bay, in mineral water and tap water. This method is highly promising and has many advantages such as simplicity, sensitivity and reliability. The project intends to take further these advantages to optimise voltammetric procedures for the speciation of arsenic in natural systems: waters, plants and urine. This will include the development of smaller electrodes that are potentially much more efficient for the detection of As and other toxic metals of interest such as Mn, Sb or Hg. The optimised procedures/sensors will be tested on-site in a specifically designed analytical system that will be developed in collaboration with an industrial partner. This system should be reliable, robust, easy to use and battery powered to allow rapid on-site measurement. It is expected that a first commercial system will be available within two years.