The reproducibility errors discussed in yesterday's blog 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. In the example shown below, 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?
No comments:
Post a Comment