We have noticed that since the amount of zinc in the Jones reductor is so large and the sample amount small in comparison, once we pass the 100 mL sample mixture, then the 100 mL of sulfuric acid and finally the 100 mL water that was used to rinse the beaker, a small amount of sample stays in the sample, and we obtain a low Assay result (around 97%). However, if we do a second/third wash of the column (an additional 100 mL of sulfuric acid and 100 mL of water), we obtain results within specification. That confirmed that the amount stated in the monograph is not enough to "push" the complete 100 mL of sample mixture through the column.
Is it allowed to perform a second/third wash to the column to ensure the complete pass of the sample or would this be considered a deviation to the method on the ACS monograph?
