30 Reference Materials for the Measurement of Metals in Workplace Air

Abstract For the production of filters coated with metal oxides an aqueous metal salt solution is injected into a hydrogen/oxygen flame of a particle generator leading to the pyrolysis of the metal salts into nano-scaled metal oxide dust. The particles are introduced into a large sampling chamber (20 m³) via a dust tunnel (20 m). So far, the system was tested for Zn, Cu, Pb, Co, Ni, Mn and In but it should be suitable with all metals obtainable as soluble metal salts. For sample generation an eight-fold sampling system was developed for the GSP sampler. The constancy of the flow rate is assured by critical orifices. Up to fourteen of these systems can be operated to produce 112 samples in parallel. Nevertheless, for the production of a reference material a significantly higher number of samples will be needed. To achieve this aim the environmental conditions of the dust generation have to be stabilized for consecutive runs. The major problem was the temperature rise of the dust channel during the particle generation due to the heat of the flame. An additional heater was installed to work at a constant temperature of 30 °C. Three consecutive filter series were manufactured. The achieved temperature constancy of 30± 0.5 °C makes it possible to combine the successive filter series. The loadings of the combined series were Cobalt: 3.25±0.058 µg/filter, Nickel: 13.78±0.23 µg/filter, Lead: 109.5±3.0, Copper: 9.65 ±0.18 µg/filter and Zinc: 32.66±0.72 µg/filter.