Press Release Summary:
HPPS (High Performance Particle Sizer) incorporates back scatter optics to measure concentration samples without need for dilution. Non-invasive back scatter technology detects scattered light while maintaining signal quality. HPPS uses 1 disposable cell, and does not require cleaning. It is capable of moving sample cell and automatically locating optimum measurement position. Measurement sensitivity is provided for samples as dilute as 0.1 ppm.
Original Press Release:
Unique Back Scatter Optics Allow Particle Size Measurement At High Concentration
Accurate analysis of dilution-sensitive samples now possible
The unique back scatter optics in the recently introduced Malvern HPPS (High Performance Particle Sizer) are making possible the accurate measurement of a range of high concentration samples, such as suspensions and particularly emulsions, without the need for dilution. This is a significant advance since many high concentration systems are sensitive to the disruptive effects of dilution, which produce erroneous particle sizing results. Equally, it may be difficult or inconvenient to build in a dilution step.
An example of a highly concentrated system is that of silica particles used in polishing slurries for the semi-conductor industry. Here particle size distribution affects both the substrate removal rate and the surface finish. Typically slurries can contain silica at 20% volume concentration and are opaque. Classical light scattering systems fail to give accurate particle sizing data due mainly to the presence of multiple scattering, whereby light scattered by one particle is re-scattered by others before reaching the detector. HPPS back scatter optics minimise multiple scattering by automatically optimising the scattering path length.
Non invasive back scatter technology (NIBS(R)) is a dynamic light scattering technique that incorporates a unique optical configuration to maximise detection of scattered light while maintaining signal quality. The use of back scattering rather than the typical 900 detection angle, improves the sensitivity of the measurement and ensures the smallest possible interference from multiple scattering. Earlier back scattering techniques suffered from drawbacks that included the need for contact between sample and detector optics, necessitating careful cleaning of the measurement optics between samples to avoid cross contamination. The HPPS uses a standard disposable cell and because there is no contact between sample and detector, cleaning is unnecessary.
The ability to move the sample cell and automatically locate the optimum measurement position is a feature unique to the HPPS. This automated positioning ensures the setting is tailored to the characteristics of the specific sample. The optimum position for measurement is close to the centre of the cell for dilute samples to maximise the observation volume, and close to the cell wall for more concentrated samples to minimise the distance that light must travel through the sample.
The net result is high measurement sensitivity for samples as dilute 0.1 ppm and the ability to measure at a concentration up to 20vol%.