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ISO 19430:2016 pdf free

ISO 19430:2016 pdf free.Particle size analysis一Particle tracking analysis (PTA) method
The lower limit of detection in terms of the particle hydrodynamic diameter is determined (apart from sensitivity and dynamic range of the camera) by the light scattering from the particles. It is the combination of refractive indexes of the particle material and the diluent that affect the amount of light scattering the detection and tracking system. A large difference in refractive indexes results in higher scattering and therefore lower detection limit for all other parameters being the same.
Better tracking of highly scattering particles results in preferential counting of particles. The accuracy of counting is covered in 5.4.4.
Sample polydispersity affects the ability to track and therefore analyse different size fractions in the particle number-size distribution. The underlying effect is linked to the dynamic range of the video capture and image analysis. In a polydisperse sample large particles scatter a lot more than small particles making it difficult to detect or track small size particles. All the values in Table 1 are given for monodisperse samples. In the case of a monodisperse gold spheres in suspension, the lower limit of detection is typically 15 nm but can range from approximately 10 nm to 20 nm.
Measurement of particles critically depends on the ability of the PTA system to detect them. Larger particles can be detected with more ease than smaller ones. Samples that contain particles of very different sizes may therefore oversample (or overcount) larger particles. Due to the statistical nature of this measurement the particle track lengths vary. Tracks that are too short or intersecting tracks are rejected by the processing software. Some instrument manufacturers employ an optimization procedure that optimises the threshold automatically whereas some allow users to set the minimum threshold of tracks manually.
Another effect of large particles is related to their dynamics, smaller particles on average move greater distances than larger particles between frames. In some cases, these particles exit the field of view and in that case may be disregarded from the calculation. Larger particles at the same edge of the field of view are more likely to be tracked for longer thus contributing more significantly to the overall count.Conversely, a small particle outside the field of view has a greater chance of more rapidly entering the field of view than a large particle at that same position. Therefore, providing the number of particles of a given size per frame are being reported on, this in itself does not lead to a bias in the measurement.ISO 19430 pdf download.

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