One of the most common set of questons we receive from our contract analysis customers and new Malvern Mastersizrr users is what does all these number on the Mastersizer report mean ? After years of answering these questions I finally took the time to briefly explain it all ! Happy reading.
Example of a standard report
Measurement Details
The Measurement Details describe the name of the sample, name of the method used (SOP File name) and when the sample was analysed and measured.
Analysis
Particle Name, Particle Refractive Index, Particle Absorption Index
These are instrument settings required to make a laser diffraction measurement. It describes how light is refracted and absorbed by the sample.
Dispersant Name, Dispersant Refractive Index
The dispersant used and how it refracts light is also used by the instrument software to calculate the result.
Scattering Model, Analysis Model
It documents which model is used in the instrument software to calculate the result. Typically it is MIE- General Purpose.
Weighed Residual
A quality parameter that tells you how closely the raw and calculated scattering pattern matches. “As a rule of thumb “ larger values than 2- 3 % might indicate a possible problem with the particle refractive index etc… used. Some samples like certain sub-micron distributions can routinely have a residual of 5- 8 %.
Laser obscuration
A measure of how much sample has been added for measurement. Depending on the size distribution this value can range from 3 % to 20 % for wet measurements and typically 2- 6 % for dry measurements.
Result
Concentration
A calculation from the volume distribution of the sample concentration during measurement.
Span
A statistical parameter of the width of the size distribution It is the (D90 – D10)/D50.
Uniformity
A statistical parameter of symmetry of the distribution. A value of 1 is perfectly symmetrical and a value of 0 is not.
Specific Surface Area
A calculation of surface area from the volume distribution. It is not a direct measurement like gas adsorbtion (B.E.T) and just an indication of surface area, as it cannot account for sample porosity.
D(3,2) / D(4,3)
Two types of sample averages. The D(3,2) is the surface weighted mean and more sensitive to fines in the distribution while the D(4,3) is the volume weighted mean and more sensitive to the coarse end of the distribution. For more detail request the “Basic Principles of Laser diffraction paper”.
Dv(10),Dv(50) ,Dv(90)
Percentiles of the volume distribution which is useful to determine how small, average and large the size distribution is.
The D10is the value where 10% of the distribution is smaller than that value in micron.
The D50 is the median where 50% if the distribution is smaller than that size and 50% larger. So also another statistic for an average size.
The D90 is the value where 90% of the distribution is smaller than that size in microns. So an good indication of how large the sample distribution is.
Frequency graph
A graph of the size distribution that display the amount of sample in the distribution vs size.
In the example above we can see a small amount of the distribution is smaller than 1 um ( fines) while the mode is around 30 um with no material present above 100 um. It is normally used qualitatively to get a visual idea of the size distribution.
Result table
We normally report the % Volume Under on our standard report which is the percentage of the distribution smaller than the size. E.g. at 2.13 um we have 10.95 % of the distribution smaller than 2.13 um. It is similar concept as the percentage passing on a sieve.
Other tables we can report (on request) is the % Volume above which is the inverse of the % Volume Under – so the amount of the distribution larger than the size or similar to the percentage retained on a sieve.
The 3rd table sometimes used (again available on request) is the % Volume In which is the percentage of the distribution between sizes
In the example above 0.7% of the volume size distribution is between 0.594 and 0.675 um.
If you have any questions about the standard laser diffraction reports please do not hesitate to get in touch with us.