Performance of the Halogen Technology for Determining the Moisture Content of Nanoparticulate Powders

Abstract

Powder moisture content is a crucial parameter in many research and industry applications. Moisture content is required before conducting experiments, particularly when assessing nanomaterial risk using dustiness methods. Halogen moisture analyzers based on halogen technology are claimed to be more advantageous than other techniques for determining the moisture content of powders; they are rapid, accurate, reliable, cost effective and easy to use. However, no data in the open literature verify this claim, despite worldwide usage of these devices. In this technical note, we studied the performance of a representative halogen analyzer (HR83 manufactured by Mettler Toledo) for determining the water content of powder materials by comparing it with 3 reference thermogravimetric instruments. Our comparison covered 14 powders, of which 12 are nanoparticulate and representative of those most produced on an industrial scale. These test powders are of various chemical compositions (TiO2, SiO2, CuO and Gypsum CaSO4(H2O)1/2) and specific surface areas. Halogen technology was validated using 3 reference powder materials with known moisture contents. The biases on the reference values are within ±10% and the fairly small linearity in these biases confirmed the accuracy. The study gives good measurement repeatability using the halogen technology (5% in mean CV) and no significant differences in measured moisture content compared with reference devices were revealed. A relationship between the moisture contents and the powder specific surface areas (SSAs) was also highlighted. The powders characterized by high SSA values have the highest moisture contents. Overall, these results support the suitability of using the halogen technology to measure powder water content. More specifically, small companies and laboratories, which cannot invest in expensive sophisticated instruments, can effectively rely on halogen technology for this purpose.