EOS recently patented the innovative SPES² technology with the aim of improving the information retrieved from each measured particle. The introduction of proper additional measurements further improves the EOS multiparametric approach. EOS developed this approach through the SPES² patented technology since 2017, basing on previous implementations realized within the EOS laboratories. The additional multiparametric approach is of utmost importance in characterizing samples with several unknown properties, such as the cases of strongly heterogeneous suspensions.
The SPES² technology has currently been introduced to develop the EOS instrument aimed at characterizing airborne dust and/or micro- and submicron particles. The power scattered at 90° is collected and measured synchronously to the traditional SPES signals. The corresponding adimensional parameter F90° is recovered thanks to the self-reference monitoring provided by the SPES sensor. This quantity provides the information corresponding to that obtained by the traditional OPC devices exploited for airborne particle measurements and for traditional particle sizer exploited for wet sample analysis.
An example of the superior insight allowed by a SPES² device is reported in figure for airborne particles. The top panel shows the traditional SPES data. The additional powerful SPES² data set is represented in the bottom panel. The forward scattering parameter, F0°, is just obtained from the SPES data and represented in grey tones, while the additional F90° histogram is shown in blue. As it is clear, a bifurcation is evident in the F90° population, while it is completely hidden in the SPES data, both representations. A discrepancy of a decade is there in the F90° data for several fixed abscissas values. Note that the same bifurcation would be completely invisible to a traditional instrument as Optical Particle Counter (OPC), operating with the one F90° parameter. This bifurcation shows a clear twofold population with rampant different optical properties.
The SPES² technology has been recently exploited for developing an instrument devoted to characterising the optical properties of airborne dust in the environment, with a current application within the OPTAIR research project funded by the Italian National Research Antarctic Program. The instrument is continuously working since November 2018 at Concordia Station, DomeC, on the East Antarctic plateau.
(in figure) The traditional SPES data (top) and the SPES² corresponding population (bottom), constituted by the adimensional forward scattering amplitude (black), obtained form the left panel data, and the additional F90° scattered adimensional intensity (blue). Notice the presence of a bifurcation in the F90° population.