Compatibility of Particle Size Analysis Periods

Mastersizer 2000 and Mastersizer 3000  

Particle Size Analyzers Compatibility  

 

To ensure compatibility of methods between different laser diffraction particle size equipment, the following three variables need to be considered. 

• Particle size calculation parameters – optical properties, analysis models, etc. 
• Measurement parameters – equipment size range, obscuration range, measurement time, etc.  
• Sample dispersion state – may be affected by pump and stirrer speed, ultrasonication time, and dispersion device pressure settings. 

If all variables are correctly passed and the size is within range on both instruments, excellent agreement can be achieved. When particles are close to the maximum or minimum size, differences appear due to the enhanced performance of the MS3000. 

 


The purpose of this note is to compare the calculation, measurement, and dispersion settings between the Mastersizer 2000 and Mastersizer 3000 systems. If variables cannot be directly transferred, tests are suggested to determine appropriate settings for comparable results. 

 


The ease of method compatibility between systems depends on the accuracy of the initial method. Detailed explanations on method development and validation are provided in separate application notes [1, 2, 3]. 

Particle Size Distribution Calculation

 


Laser diffraction instruments use optical models to interpret measured scattering data and calculate particle size distributions. 

 


Optical Properties 

 


The most comprehensive optical model is Mie theory. This requires the user to input the optical properties (refractive index and absorption index) of the sample and the dispersant.
Both Mastersizer 2000 and Mastersizer 3000 use correct values of refractive index and absorbance (imaginary refractive index), selected from a database, which can be augmented with new values. Generally, there is no difference in how optical properties are defined between the Mastersizer 2000 and Mastersizer 3000. 

 


However, to ensure accurate method transfer, it is important to verify the correctness of the optical properties. Using incorrect optical properties can lead to different results from each system due to differences in detector design. 

 


The above image shows the results of measuring a calcium carbonate sample using the default (incorrect) optical properties of Refractive Index=1.52, Absorbance = 0.1 on both Mastersizer 2000 and Mastersizer 3000. It shows differences in differential distribution shape and significant change in Dv10 value. 

Yet, with correct optical properties, excellent result compatibility between the systems is achieved. Figure 4 shows results obtained from analyzing the same calciumcarbonate sample on both devices using Refractive Index 1.6 and Absorbance 0.01. 

 

The results indicate greater similarity between the particle size distributions, with measured percentiles on both devices falling within ISO limits for repeatability [4]. 


Both figures also show the analysis residual (lower values indicate better data fit) for each set of optical properties. Using 1.6 and 0.01results in reduced residuals reported by both devices, indicating that the difference between measured and calculated scattering data was reduced, suggesting these optical properties better suited for the sample. 

 


This example shows that proper optical properties enable good agreement, but attention should be paid as incorrect optical properties can still yield similar results on both systems. 

Analysis Models
 

Diffraction instruments use analysis models alongside optical models to ensure more accurate data interpretation across distributions of different widths. For example, the general purpose model fits most powders, precipitates, and emulsions while narrow mode models may be better suited for graded or standard materials. 

 


Table 1 compares the analysis models available on Mastersizer 2000 and Mastersizer 3000. While model names may differ, most analysis models can be directly compared between Mastersizer 2000 and 3000. 

Measurement Parameters 

 


To achieve equivalent data from both systems, comparable measurement parameters must be set, taking into account the absence of a direct comparison of the effects of these parameters on results. 

 


Equipment Size Range
 

Enhancements in the measurement range of the Mastersizer 3000 may cause differences in results when the sample lies at the maximum or minimum of the equipment measurement range [6]. 

 

 

 

Figure 5 shows the results of a coffee sample measured on both devices. Excellent agreement was achieved between systems in this case. This sample also uses a narrow mode model to enhance data fitting. 

Samples containing particles over 2000μm may show more results on the Mastersizer 3000, while cut-off may occur on the Mastersizer 2000 results. In these cases, limiting the size range used in analysis on the Mastersizer 3000 can enhance comparability of the results. 

 


Obscuration Range
 

For laser diffraction measurements, the obscuration range linked to concentration should be selected to collect sufficient scattering data while minimizing multiple scattering.
If too little sample is added to the dispersant, results may not be reproducible due to low signal-to-noise ratio. Measurement reproducibility can be tested by measuring separate sub-sample samples. 

If obscuration is too high, measurements are affected by multiple scattering, causing a decrease in measured particle size at higher obscuration. The enhanced optical design of the Mastersizer 3000 significantly reduces the effects of multiple scattering. Therefore, performing obscuration optimization is important. 

 

Particularly for samples smaller than 1μm, it is necessary to perform obscuration optimization to stably measure particle size. 

 

 

 


Figure 6 shows the results of obscuration optimization performed on the same emulsion sample measured on both devices. Here, Dv10, most sensitive to changes in fine particles, is plotted alongside obscuration. In this case, the Dv10 measured on the Mastersizer 2000 starts to decrease by more than 1% as obscuration increases. In contrast, the size decrease with increased obscuration is much more gradual on the Mastersizer 3000. 

Since multiple scattering is dependent on particle size, it’s advisable to use an obscuration range appropriate for the particle size, as seen in Table 2. 

 

Sample	Obscuration
	Mastersizer 2000	Mastersizer 3000
Wet ( >20μm)	5 – 25%	5 – 25%
Wet (1-20μm)	1 – 10%	1 – 13 %
Wet(   <1μm)	1 – 5%	1 – 8 %
Dry              This article may have been translated automatically {{ product.product_name }} {{ product.product_strapline }} {{ product.product_lede }}