Abstract
The increase in environmental levels of platinum can in part be attributed to the introduction of motor vehicle catalytic converters. Quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) has been evaluated as a analytical tool for the determination of platinum in environmental samples, such as vegetation, roadside dust, soil and sediment. Instrumental parameters were studied and a forward power of 1.4 kW and nebuliser flow rate of 0.95 1 min-1 were shown to give the optimum signal response for the 195Pt+ isotope. A detection limit of 0.12 ng ml-1 was achieved. Iridium was shown to be the most suitable choice for use as an internal standard with the 191Ir+ isotope being monitored. Various digestion methods were studied with aqua regia / hydrofluoric acid open vessel digestion being found to give good recovery for 2 certified reference materials, NIST 2556 (Used Autocatalyst, Pellets) and 2557 Used Autocatalyst, Monolith) with concentrations of 681 (38) mug g-1 and 1085 (32) mug g-1 respectively [certified values 697.4 (2.3) mug g-1 and 1131 (11) mug g-1]. Attention has been given to the problem of spectroscopic interference on 195Pt+ from hafnium oxide. Various correction methods were evaluated with a modification proposed to a previous method of mathematical correction being found to provide the best correction for the 179Hf16O+. An 'in-house' reference sample was prepared from a used catalytic converter and its platinum content of 3563 (176) ng g-1 established through inter-laboratory and inter-method procedures. Common rye grass (Lolium perenne) was shown to uptake platinum from both solid and liquid platinum-containing matrices. The methods developed were applied to a study of roadside dust samples taken from a busy section of the London M25 orbital motorway. The measured platinum levels of up to 194 ng g-1 agree with published literature from other European countries and represent a useful contribution to the knowledge concerning roadside platinum in the UK.