Do you know the method of heavy metal detection in HPMC hollow capsules?

The content of heavy metals in HPMC hollow capsules should not exceed 10ppm.

Sampling method: Randomly drawn samples from production batches
Test method: take the residue under the residue ignition item, add 0.5ml nitric acid, evaporate and dry until nitrogen oxide vapor no longer emits, after cooling, add 2ml hydrochloric acid, place it in a water bath to evaporate to dryness, then add 15ml water, dropwise add TS Ammonium to phenol indicator is light red, add 2ml acetate buffer (pH=3.5), dissolve with slight heat, transfer to Nessler tube, dilute to 25ml with water, and use this tube as tube a.

Transfer the quantity of reagent used to prepare the test solution to a porcelain evaporating dish to evaporate to dryness, add 2 ml of acetate buffer (pH = 3.5) and 15 ml of water, dissolve by heat, transfer to a Nessler colorimetric tube, add a quantity of Standard lead solution, then diluted with water to 25 ml, put this tube into tube B. Add 2 ml of thioacetamide TS to test tube A and test tube B respectively, mix well, let stand for 2 min, look down on the vertical axis of the test tube against a white background, and compare the colors. Heavy metal content is NMT 10ppm (0.0010%).

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