The mass-size distribution of aerosol particles is normally obtained by gravimetrical analysis using microbalances. This is a very time consuming and labour intensive procedure especially when the samples only contain very small amounts of material. With the MR250, Ancon has developed a novel technique that enables the mass-size distribution to be obtained very quickly without tedious gravimetrical analysis.
The MR250 is a companion product for the Aero Select negates the need for laboratory analysis, providing seven channels of resolution in the microparticle range from 250nm to 20μm, with sensitivity for sample masses less than 10 nanograms. Used in combination with the MR250’s user-friendly software, histograms showing the total mass-size distributions of aerosol samples collected by the Aero Select can be obtained in minutes.
An example of a mass-size distribution measured using the MR250 is shown in figure 8.1. A small amount (less than 0.5g) of titanium dioxide powder (Aeroxide® TiO2 P 25) was atomized using Ancon’s Aerosoliser, and samples of the resulting aerosol were collected using an Aero Select over a period of about 4.5 minutes. The aerosol samples were then analyzed in the MR250 to obtain the mass-size distribution.
The TiO2 mass-size distribution shows a much greater contribution from larger particles than is seen in atmospheric aerosol, with an obvious peak in the 4 – 8μm range. The average primary particle size for this TiO2 powder is specified by the manufacturer as 21nm so clearly this material exhibits a strong tendency to form large agglomerates or aggregates of particles. The total mass concentration over the range of 250nm to 35μm is 827μg/m3.
Figure 8.1: Example of a TiO2 mass-size distribution obtained using the MR250.