Knowledge introduction about particle size detection No.2

In the last issue, we introduced some basic knowledge of particle size testing. In this issue, we will introduce particle detection knowledge from the perspective of particle size detection methods.

Regarding the particle size detection method, we must first understand and bear in mind that in particle detection, there is no method that can solve all the problems of particle detection. Therefore, according to different particle size and different types of samples, we must select the appropriate method for detection. This is also the reason for the different particle detection methods.

The commonly used particle detection methods are shown in the following figure. We will mainly introduce the five methods of red labeling, which are also based on the principle of these methods.

1. Laser diffraction method

Laser diffraction method schematic diagram:

The advantages and disadvantages of laser diffraction are introduced:

Advantages: simple operation; compatible with dry and wet detection; on-line detection; wide detection range 1μm-2000 μm; no calibration; rapid detection;

Disadvantages: The resolution is not high; the sensitivity is not high; the result is based on the mathematical statistical model; only the micron-level sample can be detected; the optical parameters need to be set; the results of different brand instruments have large deviation;

2. Principle of dynamic light scattering

Dynamic light scattering schematic diagram:

The advantages and disadvantages of dynamic light scattering:

Advantages: simple operation; detection of nanoparticles and submicron particles; on-line detection; no need to set optical parameters;

Disadvantages: low sensitivity; low resolution; only wet detection; only detect samples below the micron level; results are based on mathematical statistical models;

3, the resistance method

Resistance method working principle diagram:

The advantages and disadvantages of the resistance method principle:

Advantages: high resolution; high sensitivity; particle counting; measurement results independent of color and refractive index;

Disadvantages: Only wet detection; must use electrolyte, can not detect organic samples; dynamic detection range, prone to clogging of holes; count efficiency is low;

4. Photoresist method

Photoresist schematic diagram:

The advantages and disadvantages of the photoresist principle:

Advantages: high resolution; high sensitivity; particle counting; measurement results independent of color and refractive index ;

Disadvantages: Dilutions are required for the detection of high concentration samples; Dynamic detection range; Unable to detect very small particles; Calibration of the instrument is required on a regular basis;

5, microscopy

Microscopy is divided into dynamic microscopy and static microscopy.

Principle diagram of dynamic microscopy:

Pros and cons of dynamic microscopes:

Advantages: Observable particle shape ; Compatible with dry and wet detection; Convenient on-line detection;

Disadvantages: dynamic detection range; the sample is difficult to disperse when dry detection; the amount of detectable sample is less;

The working principle of static microscope:

Static microscope advantages and disadvantages:

Advantages: high resolution; observable particle shape; broad detection range;

Disadvantages: It is difficult to do on-line testing; samples are relatively difficult to disperse; detection takes time; it is difficult to detect very small particles;

This article describes the commonly used five particle detection methods, many particle detection methods, but no one method can solve the particle detection problem, so do not blindly follow the trend or choose according to parameters in the particle detection, the best for their own is the best of.

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