The content of heavy metals in HPMC hollow capsules should not exceed 10 ppm.
Random samples taken from production batches
Take the residue under the ignition item, add 0.5ml nitric acid, evaporate and dry until the nitrogen oxide vapor is no longer emitted, after cooling, add 2ml hydrochloric acid, place in a water bath to evaporate to dryness, then add 15ml of water, drop TS ammonium to phenol The indicator was light red. Add 2ml of acetic acid buffer (pH=3.5), dissolve with slight heat, transfer to a Nessler tube, dilute to 25ml with water, and use this tube as tube a.
The transferred amount of reagent is used to prepare the test solution to the porcelain evaporating dish and evaporate to dryness, add 2 ml of acetic acid buffer (pH = 3.5) and 15 ml of water, dissolve it by heat, transfer to the Nessler colorimetric tube, and add a quantity of The standard lead solution is then diluted with water to 25 ml. This tube is tube B.
Add 2ml of thioacetamide TS to test tube A and test tube B respectively, mix well, and let stand for 2 minutes. Look down at the vertical axis of the test tube against a white background to compare the colors. The content of heavy metals is NMT 10ppm (0.0010%).