An improved method for sampling and analytical measurement of aerosol platinum in ambient air and workplace environments.

In this study we critically examined with both field and laboratory experiments key components of extant methods for measurement of aerosol soluble platinum in ambient air and workplace environments. Our goal was to develop an improved method for soluble platinum measurement that could be readily implemented in the field and laboratory using readily available modern analytical tools, and in parallel provide insight into factors influencing the robustness of specific aspects of measurement methods for soluble platinum. Experiments addressed sampler type, filter media and pre-cleaning, extraction solvent and volume, extraction time & energy and materials composition, with the objective of optimizing each specific component and promulgating strategies for improving signal/noise and precision. We used basic clean-room protocols and applied ICPMS tools to address these objectives. We document a method that provides for measurement of soluble platinum at the 0.02 ng/m level (8-h sample at 2 L/min). Of the four samplers evaluated (IOM, closed-face cassette, and two parallel particle impactors), the IOM exhibited the best precision. The three filter substrates evaluated (Teflon, MCE, PVC) performed similarly in most challenges, however, overall, we conclude that MCE media is the most robust collection substrate for soluble platinum measurements. To achieve the lowest detection levels, it is critical to pre-clean the filter substrates. The use of a 0.07 M HCl extractant (in preference to a water extractant) is recommended - platinum recoveries, particularly from real-world samples, are higher and more consistent with the HCl extractant. The outcomes of the extraction kinetics experiments suggest that an extraction time of 60 min may improve the method performance with 0.07 M HCl but degrade the performance with water, in comparison with a 30-min extraction period. The use of sonication in preference to a table-top shaker is recommended for energy input during extraction.