The optical performance of a laser diffraction system is verified by measuring standard reference materials. The performance of every laser diffraction optical bench produced by Malvern Panalytical is tested using a range of National Institute of Standards and Technology (NIST) traceable latex standards. A range of latex sizes is required to produce scattering data over a wide enough angular range to test all of the detectors. When a correct scattering signal is recorded on all of the detectors, then the measured particle size will be within a certain tolerance of the specified latex size.
The table below shows the measurement of a latex sample as run over 100 different Mastersizer 3000 optical benches – including average, maximum, and minimum values – compared to the target size range. Table 1 also shows the relative standard deviation (RSD) over the 100 measurements. The RSD is less than 1% for all latex sizes, showing reproducibility better than the ISO standard states for repeatability of a single sample.
Optical bench performance is only part of a laser diffraction system; it is also important to test the performance of the dispersion units, as these are responsible for accurately presenting the sample to the optical system. Different requirements of a sample are required to test the performance of the dispersion unit; the material must have a broader size distribution and must also require some energy to suspend and/or disperse it so that the dispersive performance of the accessory is tested.
Table 2 shows the reproducibility of 100 Quality Assurance Standards (QAS) samples measured across our dry dispersion unit (Aero S) and wet dispersion units (Hydro MV, Hydro LV, and Hydro EV). When data from all wet units is combined, the RSDs are less than 1% – showing excellent reproducibility across the range of dispersion units; the RSDs for individual dispersion units are even lower.
This testing on the Mastersizer 3000 optical bench and dispersion units provide you with confidence that if a particle size measurement result is outside the standard deviation, it is likely an issue with your sample or measurement technique, and not the Mastersizer 3000. The level of agreement between the optical bench and dispersion units simplifies the process of transferring methods and specifications between sites and different dispersion units. Often product specifications are established on particle size analyzer #1, without any consideration of what level of deviation can be expected from particle size analyzers #2 and 3 located at production sites. This study illustrates what is possible with the Mastersizer 3000.
Not all Laser Diffraction systems are the same, nor go through similar rigorous testing as shown above, to ensure they meet the highest level of accuracy and reproducibility.
Choose the gold standard for particle sizing – the Mastersizer 3000.