Posted by: Glow-worm PJ28 JAN 2010
Palladium is a silver-white ductile metal, in the platinum group, with an atomic number of 46. It was discovered in 1803 by the English chemist William Hyde Wollaston during a study of platinum ore. Russia and South Africa produce 93 per cent of the world’s palladium, with smaller quantities mined in Canada and the US. Natural palladium contains six stable isotopes, with a further 25 that are radioactive.
Palladium alloys are used extensively in dentistry, electrical circuitry, watch-making and the jewellery industry. It is prized for its catalytic properties and is an essential component in the catalytic convertors of motor vehicles.
Palladium also has uses relevant to health care. In nuclear medicine, the unstable isotope palladium-103 has been employed as an alternative to prostatectomy, using a technique known as brachytherapy, or seeding.
The seeds, roughly the size of grains of rice, are titanium casings filled with palladium-103 and are implanted into the prostate. The procedure is non-invasive, and often performed on an outpatient basis.
In pharmacy, palladium has also found a role in blood glucose testing, as a component of the electrodes used in blood testing meters. Glucose in the blood sample is oxidised by glucose dehydrogenase contained on the test strip, causing a corresponding reduction of a hexacyanoferrate mediator.
When a voltage is applied from the meter, in the presence of the palladium electrode, the hexacyanoferrate is reoxidised, resulting in an electron flow that is measurable and directly proportional to the concentration of glucose in the blood, resulting in the quick and accurate measurements with which we are familiar today.
Researchers at the University of Illinois have recently reported the development of a palladium-containing photocatalyst, activated by visible light, which results in the release of oxidising agents that kill harmful bacteria. The palladium nanoparticles continue to catalyse the reaction for up to 24 hours after the light source is extinguished, enabling purification of drinking water and sterilisation of surgical equipment to be activated with sunlight or standard indoor lighting.
And, finally, medicinal chemists at the University of Maryland have developed a palladium catalyst that aids the chemical synthesis of colchicine, which has been in short supply of late in the US.