Hello, I am having trouble with a new box of LMW Chitosan which I purchased from Sigma-Aldrich. The old box that I used before, was product of Iceland, and the new one is the product of U.S., both are Sigma-Aldrich. My emulsion protocol worked consistently with the old one, but the new box chitosan has some metallic residues and doesn't make stable emulsion with my protocol. Did anyone observe the same problem? Would you recommend any other LMW Chitosan Supplier?