Table of contents 1 Why is particle size important?
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- Điều hướng trang này:
- DYNAMIC LIGHT SCATTERING
| INCLUDING THE ERROR
The reproducibility errors discussed above should be investigated and minimized because they play an important role in the final setting of a specification. Once the specification based on product performance has been determined, then the final specification must be narrowed by the error range (ref. 11). In the example shown in Figure 16 the specification for the D50 is 100 +/- 20% (or 80–120µm) based on product performance. If the total measurement error is +/- 10% (using USP<429> guidelines for the D50 value), the specification must be tightened to ~90–110µm (rounded for simplicity) in order to assure the product is never out of the performance specification. For example, if the D50 is measured to be 110µm, we are certain the D50 is actually less than 120µm even with a maximum 10% error. This is why it is important to create robust standard operating procedures for any material we wish to set a published specification for. Any combination of high measurement error (usually stemming from non-optimized method development) and tight specifications will make meeting that specification more difficult. Why make life harder than it need be? DYNAMIC LIGHT SCATTERING The primary results from dynamic light scattering (DLS) systems are typically reported as an intensity distribution. Key values included in DLS-based specifications are the intensity-weighted average (often called the “z average”) and the polydispersity index (PI), which quantifies distribution width. Mean values for one or more peaks can be calculated and included in the results. The results can be transformed into a volume-based or number-based distribution when comparing to other techniques such as laser diffraction or microscopy. figure 16 | BUILDING SIZE SPECIFICATION TO INCLUDE ERROR SOURCES If the total measurement error is +/- 10%, then the specification must be tightened in order to assure the product stays within performance specification. 13 tải về 7.54 Mb. Chia sẻ với bạn bè của bạn:
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