Sieving has been around since the time of the ancient Egyptians and can be considered the backbone of particle size technology. Sieving’s continuing popularity is due to the technique’s fundamentally simple principle and methodology, historical reference, and cost effectiveness. Several instrument components involved in a sieve analysis can be quality controlled, making the technique applicable to various industries including pharmaceutical, industrial, agricultural, and chemical.
A sieve analysis consists of using a single or set of screens (typically woven wire mesh), decreasing in opening size, to separate or classify a sample. Several mechanisms are used to disperse the sample and transport it through the screens (i.e. vibration, air entrainment or flowing liquid). While considered relatively low resolution, sieving’s practical applications lend itself well to quality control specifications. ASTM E-11 establishes acceptance criteria for the woven wire mesh opening tolerances of standard sieve sizes. For optimal quality control, PTL verifies its in-house sieves with an external vendor for compliance with the ASTM E-11.
While sieving may appear rudimentary compared to more modern instrumental particle sizing techniques, it still requires several important considerations to obtain the best repeatable and precise results. Several factors must be considered when developing a robust sieving method or performing a routine quality analysis. Sample size, sieving duration, controlled agitation parameters and end point determination are all critical method variables which need to be addressed. PTL’s various sieving capabilities and strict attention to detailed procedures, which incorporate the topics above, ensure that the best possible results are generated.
Some sample properties (such as hygroscopic or electrostatic tendencies), can pose significant analytical difficulties, especially at small sieve sizes. As a result, using an appropriate sieving technique is of utmost importance. Such sample types may be suspended an inert liquid media prior to analysis or aided with flow enhancers.
Sample amount is not an easy question to answer, since it depends on the sieve technique and general nature of the material, as well as the methodology that will be used. Ideal sample amounts are specific to the apparatus with 100 grams preferred for Standard Sieve Stacks and 10 to 20 grams for Sonic Sifter and Air Jet.
Questions on sample needs — please contact us to share specifics about your sample and options for suitable sample quantities.
PTL’s Sieve Analysis Department recommends sieving from 45 um and above for Standard Sieve Stacks and Sonic Sifter Sieve Stack. Air Jet Sieve is capable of sizing down to 20 um if necessary but alternative particle sizing technique is recommended.
Sieve results are reported as the differential weight percent retained on each sieve as well as the cumulative weight percent less than the sieve size. Specific reporting requirements are easily adjusted based on the client’s request. For more information on how PTL can employ sieving to assist with quality control specifications, third party verification, method development and/or transfer please give us a call.
Particle Technology Labs has a variety of options to support our clients sieve needs including:
• Hosokawa Micron Air Jet Sieve (MAJS) with standard 200 mm diameter, half height sieves (if multiple sieves requested, analyzed one at a time)
• VariSifter™ Sonic Separator VS1000 Sieve Stack (45 µm and above, up to 6 sieves)
• Dry Sieve Stack (up to 7 standard 8″ diameter sieves)
• Wet sieve stack (up to 7 standard 8″ diameter sieves)
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