Our patented Single Particle Extinction and Scattering SPES / SPES² technologies uniquely and innovatively exploit the light scattered by micro- and nanoparticles to characterize complex mixtures and heterogenous liquid samples and aerosols.
Dedicated data analysis algorithms provide reliable and meaningful information, boosting R&D and quality control processes during lab-scale development, industrial production, and advance monitoring of particles in biological, industrial, and environmental fluids.
- Calibration-free Optical Classification, Absolute Particle Size Distribution, and Numerical Concentration of each individual particle population, regardless of polydispersity and particle mixtures.
- Quality Control of particle properties such as porosity, wetting, aspect ratio, payload, impurities and shelf-life, without intermediate steps (e.g., purification/filtration).
- Direct measurement of particle behaviour and formulation stability in heterogeneous non-filtered target fluids, including biological, industrial, or environmental samples.
- High-Resolution Continuous Flow Analysis of particles, ready to integrate to other analytical devices and systems, such as cFFF separators, small-scale chemical reactors and pilot lines.
- Advanced statistical methods such as Oversize and Principal Component Analyses (PCA) for Batch-2-Batch comparison and out-of-spec detection in product formulation, production and Quality Control.
How Does SPES/SPES² Work?
Among the various methods currently available, optical techniques offer unique advantages, placing light scattering at the forefront of analytical tools in both scientific research and industrial applications.
The scattering behaviour of a particle is influenced by numerous parameters. As a result, the simple measurement of scattering intensity or even the extinction of light by a single particle provide only a rough estimate of its size.
The complexity increases when considering a collection of scatterers, where interpreting the experimental data requires to solve ill-posed mathematical inversions.
The SPES / SPES² technologies rely on the interference of light scattered by particles, when illuminated by a laser beam focused either within the fluid flow in a cuvette or in the flux of aerosol particles.
The scattered light is measured both in the forward direction – superimposed to the focused laser beam – and at 90 degrees.
In the forward scattered light, the intense transmitted laser beam interferes with the faint scattered wavefront, creating a so-called interference pattern of intensity modulations.
This pattern is the heart of the SPES measurement because it contains multiparametric information about two key optical properties of each scattering particle.
At the same time, the 90-degree scattered intensity is analysed during the particle’s transit through the scattering region, providing additional independent data.
For each particle, three independent scattering properties are measured::
- the global attenuation caused by the particle, the extinction cross section Cext, which quantifies the fraction of incoming laser power removed.
- the particle’s polarizability α, proportional to its volume, derived from the amplitude of the constructive and destructive fringes in the interference pattern
- the total scattered intensity at 90 degrees, F90, integrated over a wide solid angle
The Extinction Cross Section Cext , the Polarizability α and the F90 signal are thus obtained for each detected, validated, and counted particle using a robust Pulse Shape Analysis scheme. This approach avoids the common pitfalls of ill-posed problems such as inversion or deconvolution.
In just a few minutes, SPES generates the EOS CLOUDS, a unique 2D or 3D histogram where data can be visually and analytically represented.
In heterogeneous samples, each particle population forms a separate, identifiable cloud, which can be selected, analysed individually and compared.
Particle size distribution, numerical concentration, oversize analysis and other statistical insights can be derived from the selected particle populations, from the entire sample or from each time frame acquired in Continuous Flow Analysis (CFA).
Advanced statistical methods such as Principal Component Analysis (PCA) can further extract unique information typically inaccessible using conventional techniques.