1. What is the size range you need to measure? Unfortunately, no one technique can measure all possible particle sizes, so the range needed will narrow the potential systems which can be used. If your application has a very wide range of sizes, try to narrow that range down to the fraction of that range that is most important. For example, are the smallest particles most important or the largest? Refine the system choice based on a system that best handles the most important part of the overall size range.
  2. What exactly do you want to measure and why? Particle analyzers use many different techniques to arrive at measurements. In order to figure out what technique will work best for your application, you need to define what you are trying to measure and why. This will help narrow down the appropriate technology type for the application.
  3. Are you trying to characterize different particle types in a single sample? The large majority of particle “analyzers” only perform “particle sizing” based on a signal proportional to the particle’s volume. This, combined with an assumption that “all particles are spherical”, produces a single number, Equivalent Spherical Diameter (ESD) as a measure of each particle’s “size.” Imaging techniques, on the other hand, can measure many different particle shape attributes which can be used to automatically differentiate different particle types in a heterogeneous mixture.
  4. In what “state” should the measurements be made? In many cases, measurement of the particles in the “native state” may not be possible; for instance, a slurry of particles at high percent solids is very difficult to measure with most techniques. When dilution is necessary, care must be taken to use a diluent that is inert to the particles under study and does not alter them once diluted. Just because the raw material is a dry powder, does not necessarily mean that measuring them in a dry state is always the best method, as there can be benefits to suspending the dry particles in an inert liquid for analysis.
  5. Is measuring the count or concentration (two different measurements!) of the particles along with size/shape important? If knowing an absolute particle count, or a particle concentration is important, then some techniques will be eliminated immediately. Any “ensemble” methods, or other methods that recirculate the particles can only be used for very relative comparisons, not true concentrations. If concentration is important, make sure that the manufacturer has a well-established procedure for verifying concentration measurements (through the use of standards, for instance).
  6. How easy is it to generate reliable data? Think about your users and ask what, if any, specific expertise is required for system set-up and routine use. Then, ask to make a measurement to assess this during the selection process.
  7. Can the instrument comfortably handle all your samples? Check the particle size range and the availability of efficient dispersion units for suspension, emulsion, and dry powder analysis.
  8. Are there any features that will boost productivity? Ask about measurement times; check how easy it is to switch between sample types and assess maintenance requirements.
  9. How does the SHE performance of the system compare with others? A good dry dispersion unit will minimize the need for wet measurement, for example, cutting dispersant use. If you need containment, then assess its quality.
  10. How easy is it to tailor analysis to your precise needs? Check out the software interface, and the process required to develop methods and present your data how you want it.
  11. And finally what type of support is available, now and into the future, if things go wrong, or with a new application? Ask about provisions for on-line education and training.

Article courtesy of LabManager Magazine

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