Laser particle size analyzer is an instrument that analyzes particles through the principle of laser scattering, commonly used to determine the particle size distribution of particles in powder or liquid samples. Particle size is an important parameter for describing particle size, while particle size distribution refers to the distribution of particle size throughout the entire sample. For the particle size evaluation criteria of laser particle size analyzer, there are usually several considerations:
1. Particle size distribution range
Laser particle size analyzer usually has a certain range of particle size measurement, and the range of particle size distribution is generally determined by the model and application requirements of the instrument. The common range of particle size measurement is:
0.1 µ m to 2000 µ m, used for analysis of most powders and liquids.
Some instruments may support smaller particle sizes (such as nanometer scale) or larger particle sizes (such as millimeter scale).
Evaluation criteria: The instrument should perform particle size analysis based on the particles within its measurement range to ensure measurement accuracy within that range.
2. Types of particle size distribution
The particle size distribution is usually represented by a particle size distribution curve, and common types include:
Single peak distribution: particles are concentrated within a specific particle size range, and the distribution curve presents a single peak.
Multi peak distribution: Particles exhibit a distribution of multiple size ranges, and the distribution curve may have multiple peaks.
Evaluation criteria: The curve of particle size distribution should be able to truly reflect the actual particle size characteristics of the sample, especially for complex multimodal distributions, the instrument needs to have high resolution and accuracy.
3. Granularity calculation method
The laser particle size analyzer measures particle size through laser scattering, and the calculation method for particle size usually includes:
Volume averaged particle size (D ∝₂): Volume weighted average particle size, used to describe the total volume of particles.
Surface area mean particle size (D ₅₀): The average particle size weighted by the surface area of the particles.
Number average particle size (D ₁₀, D ₅₀, D ₉₀): These values represent that 10%, 50%, and 90% of particles are smaller than this particle size, respectively.
Evaluation criteria: Different calculation methods are applicable to different granularity distributions and application scenarios. Usually, D ₅₀ (median particle size) is widely used, reflecting the general size of particles.
4. Resolution and repeatability
Resolution: refers to the minimum difference that an instrument can distinguish between two particles of similar size. High resolution instruments can accurately measure the size of particles in close proximity.
Repeatability: refers to the consistency of results when multiple measurements are taken under the same conditions. High quality laser particle size analyzers have good repeatability and can provide stable and reliable results.
Evaluation criteria: The repeatability usually needs to be around 5%, while the resolution generally requires the ability to distinguish differences of a few micrometers or less.
5. Measure the impact of the environment
The measurement results of laser particle size distribution analyzer may be affected by the following factors:
The refractive index and absorbance of the solution: The optical properties of the medium (such as liquid) in which the sample is located can affect the scattering of laser light, so it is necessary to consider the solvent and liquid properties of the sample when measuring.
Particle shape: The laser particle size analyzer assumes that the particles are spherical, but in reality, many particles may be non spherical, which can affect the accuracy of the measurement.
Particle dispersibility: In liquid samples, the degree of particle dispersion affects the measurement results, and it is necessary to ensure that the sample is uniformly dispersed.
Evaluation criteria: The measurement of the instrument needs to consider these environmental factors to ensure the accuracy of the measurement results. Usually, calibration can be performed using standard samples or reference samples.
6. Error analysis and calibration
Instrument error: When using a laser particle size analyzer, attention should be paid to the instrument's error range, usually requiring an error of less than ± 1% -2%.
Calibration and Verification: Regularly use standard particle size samples for calibration to ensure the accuracy and reliability of the instrument.
Evaluation criteria: The instrument's error should meet the standards and have good calibration and verification procedures.
7. International standards and industry norms
In order to ensure the accuracy and comparability of measurements, the measurement method of laser particle size distribution analyzer should comply with relevant international standards or industry specifications. Common standards include:
ISO13320: This is an international standard in the field of particle size measurement, which defines the performance requirements and measurement methods for laser particle size analyzers.
ASTME2925: This standard is specifically designed for the calibration and use of particle size analysis instruments, ensuring consistency and accuracy of measurements.
Evaluation criteria: The use of instruments and measurement methods should comply with relevant international or industry standards to ensure the reliability and wide applicability of test results.
Summary:
The particle size evaluation criteria of laser particle size analyzer include particle size measurement range, particle size calculation method, resolution and repeatability, influence of measurement environment, error analysis and calibration, and compliance with international standards. Good instrument performance and operating standards can ensure the accuracy and consistency of measurement results.