Food and medicine

index        Requirements (taking red iron oxide as an example)        illustration

Fe₂O₃ content: ≥98.0%  To ensure stability of tinting strength.

Water-soluble matter ≤0.5%  (To prevent dissolved impurities from affecting the efficacy of the medication)

Acid-insoluble matter: ≤0.3%  To Guarantee purity
     

Heavy metal limits

Lead (Pb) ≤ 0.001%

Arsenic (As) ≤ 0.0003%

Cadmium, mercury, etc., must not be detectable.     To comply with ICH Q3D Elemental Impurities Guideline.
Microbial limits    The product must pass tests for total bacterial count, E. coli, Salmonella, etc.         Especially oral solid dosage forms.
Particle size distribution       Normally  D90 ≤ 10 μm.        Being too coarse will affect the uniformity of the coating.

Incandescent weight loss       ≤4.0% (Iron Oxide Purple/Black )      Reflection of  moisture and volatile matter content.