1. Can I use a sinker when the USP monograph does not specify one?
Typically if a sinker is needed in a dissolution test the procedure will mention the fact. Where the use of a sinker is not specifically mentioned in the procedure, it is safest to assume that the use of sinkers would represent an alternative procedure.
2.How can I find the right filter for my dissolution procedure?
The right filter will not adsorb the analyte when the dissolution sample solution is filtered. A number of filter materials are available increasing the probability that a good match can be found. The adsorption of the analyte to the filter may be saturable, meaning that it can only adsorb a certain amount of the analyte. If that is the case, a specific discard volume of sample solution filtrate can be found that allows subsequent filtrate concentration to be representative of the concentration of analyte dissolved in the sample. Typically milliliter increments of filtrate are passed through the filter cartridge and collected separately. The response of the analyte is measured in each increment and compared with the unfiltered solution. The amount of discard is determined from the results.
3. What is the purpose of the PVT?
USP considers adherence to measurable dimensional and operational parameters to be a critical component of apparatus suitability. However, without a challenge to the apparatus demonstrating the ability to produce dissolution results from a standard material, mechanical qualification alone does not provide sufficient evidence that the apparatus is performing satisfactorily. Furthermore, the USP PVT relies on more than the reference standard material itself. The ranges for the geometric mean (GM) and the coefficient of variation (%CV) are an integral component of the PVT and are obtained from a multinational collaborative study conducted for each new lot of reference standard tablets. Those two statistics, GM and %CV, help the laboratory using the reference standard determine if their results are accurate within the context of ISO 5725-6, Accuracy (Trueness and Precision) of Measurement Methods and Results—Use in Practice of Accuracy Values. Accuracy is comprised of trueness and precision, which are embodied in the geometric mean and %CV, respectively. A discussion of these concepts can be found in an article by Walter Hauck, et al. in Pharmacopeial Forum 33(3), “Proposed Change to Acceptance Criteria for Dissolution Performance Verification Testing.”
4. Can I use peak vessels?
<1092> mentions peak vessels as noncompendial apparatus that may have some utility with proper justification.
5. Why aren’t the recommendations in the USP Dissolution Toolkit found ?
The USP Dissolution Toolkit contains enhanced mechanical calibration information. Agreement exists that additional controls can be imposed by tightening the mechanically measured attributes of Apparatus 1 and 2, insufficient data exists to determine the appropriate degree of change or that such tightening would necessarily improve the quality of the dissolution results obtained. Because the chapter is harmonized, any change to the description of Apparatus 1 or 2 would have to be agreed by the Pharmacopeial Discussion Group comprised of the European Pharmacopoeia, the Japanese Pharmacopoeia and USP.