Cake washing test procedure

GTI IPCs are usually trace analyses quantitated to ppm levels versus the product concentration in solution. " The analysis can be either a limit (pass/fail) or quantitative test performed at point(s) where the impurity can be reduced or removed (e.g., product solution extractions, wet cake washes, or crystallizations). Quantitative GTI results are usually needed for process development samples to track the level of GTI removal for the procedure. "" Limit tests are routinely used for manufacturing IPCs. The method validation follows those suggested by the ICH (specificity, linearity, limit of detection, solution stability, spike, and recovery). 

Vacuum and pressure laboratory filtration assemblies are shown in Figure 11.7. Mild agitation with air sometimes may be preferable to the mechanical stirrer shown, but it is important that any agglomerates of particles be kept merely in suspension and not broken up. The test record sheet of Figure 11.8 shows the kind of data that normally are of interest. Besides measurements of filtrate and cake amounts as functions of time and pressure, it is desirable to test washing rates and efficiencies and rates of moisture removal with air blowing. Typical data of these kinds are shown in Figure 11.3. Detailed laboratory procedures are explained by Bosley (1977) and Dahlstrom and Silverblatt (1977). Test and scale-up procedures for all kinds of SLS equipment are treated in the book edited by Purchas (1977). 

---