Definition
A dynamic laser particle size meter is a physical analysis instrument based on the principle of light scattering to measure the particle size distribution in suspensions or emulsions. It analyzes the fluctuation signal of the scattered light under the action of the particle under the action of Brownian motion and reverses the size information of the particle, which is suitable for the characterization of particle systems in the nanometer to micron range.
Principle
The core principle of dynamic laser particle size meter is dynamic light scattering technology, which is based on the correlation between Brownian motion and light scattering. When the laser hits particles dispersed in a liquid, the random motion of the particles causes the scattered light intensity to fluctuate over time. By recording these fluctuation signals by a photodetector and calculating their autocorrelation functions, the diffusion coefficient of the particles can be derived. The Stokes-Einstein equation is then used to convert the diffusion coefficient to the fluid dynamic diameter. The process can be expressed as:
D = kT / (3πηdh)
where D is the diffusion coefficient, k is the Boltzmann constant, T is the absolute temperature, η is the viscosity of the medium, dhis the hydrodynamic diameter.
Measurement method
The typical measurement process for a dynamic laser particle size meter includes sample preparation, instrument calibration, data acquisition, and analysis of results. The sample should be properly diluted to ensure that the particles are dispersed and at the right concentration to avoid multiple scattering effects. During measurement, the instrument collects the scattered light signal under constant temperature conditions, calculates the autocorrelation function through the correlator, and uses the inverse algorithm to fit the particle size distribution. Common inverse algorithms include cumulative analysis, the former is suitable for monovariance systems, and the latter can be used for multivariance system analysis.
Influencing factors
The accuracy of the measurement results is influenced by several factors. Sample factors include particle concentration, dispersion state, particle shape and surface properties. environmental factors involve temperature stability and medium viscosity; Instrument factors include laser wavelength, detection angle and signal processing algorithm. In addition, the presence of dust or bubbles in the sample may interfere with the signal, which needs to be controlled by filtration and degassing pretreatment. Parameters should be optimized according to standard methods to reduce system errors.
Application:
Dynamic laser particle size meters have a wide range of applications in many industrial and scientific research fields. In the chemical industry, it is used to monitor the particle size distribution of emulsions, polymer microspheres and catalysts; In materials science, it can be used to characterize nanomaterials, ceramic powders, and ink particles; In terms of environmental monitoring, it helps to analyze suspended particulate matter in water bodies; In the food industry, it is used to evaluate the stability of liquid products such as dairy products and juices. Its non-intrusive, fast measurement characteristics make it a popular tool for process control and quality inspection.
Selection
When selecting a dynamic laser particle size meter, consider the measurement range, sensitivity, repeatability, and applicable standards. For nanoparticle measurement, the instrument should have a high-sensitivity detector and a low-noise correlator; If the sample is a multi-dispersion system, it is advisable to choose a multi-angle detection model to improve the resolution. In addition, temperature control accuracy, software analysis capabilities, and compliance (e.g. compliance with ISO 22412) are also important references. Users should evaluate according to their own sample characteristics, measurement environment and data requirements, and if necessary, verify the performance of the instrument with standard samples.