Determination of platinum in environmental samples by quadrupole inductively coupled plasma mass spectrometry.

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