At Particle Analytical the method development design for a particle size distribution method is set up according to customers need. If the results are only needed for getting an idea of the particle size distribution, a screening can be suggested. However, if the method needs to be validated and handed in to the authorities, a more thorough documentation can be appropriate. Different setups for method development can be seen below, but alternative setups can be made upon request.
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Method development, particle size determination
To make a robust method of analysis by laser diffraction it is necessary to make several investigations. As standard, a method development from Particle Analytical includes the issues seen below. However, it is of course up to the customer, what the method development must include:
- Finding a suitable dispersion medium
- Test of sample stability in the medium
- Wet dispersion: Stirring speed, obscuration interval, measurement time, sonication test (if necessary), surfactant concentration (if necessary), number of required determinations to minimize the uncertainty of the result, number of required measurements per determination to ensure a representative part of the sample is measured
- Dry dispersion: Pressure determination, obscuration interval, feed rate, sample amount, slit opening, sieve (if necessary), number of dispersion balls (if necessary), number of required determinations to minimize the uncertainty of the results.
- SEM to see if the measured particles are in fact primary particles and correlate the size to laser diffraction.
- Particle size distribution by microscopy (counting minimum 3000 particles) for correlation to laser diffraction.
- Test of other batches. If different forms of the same product exists (eg. different suppliers, micronised >< non-micronised, etc), it is wise to test if the method is suitable for all types.
- Method development report including all documentation
- Method of analysis
- Certificate of analysis on the batches used for method development.
Method validation, particle size determination
USP: “It is the responsibility of the user to demonstrate the applicability of the instrument for its intended use and to validate any method prior to its adoption for routine use.”
A validation of method of analysis performed at Particle Analytical can include:
- Validation protocol including setting acceptance criteria
- Verification of sample stability
- Verification of the repeatability of the method
- Robustness (including intermediate precision)
- Critical batches
- Correlation to SEM of all batches
- Correlation to microscopy of all batches
- Validation report including all documentation.