Iohexol is a non-ionic, water-soluble radiographic contrast medium. When sourcing, you must ensure it complies with international pharmacopoeia standards such as USP (United States Pharmacopeia), EP (European Pharmacopoeia), or BP (British Pharmacopoeia). Key parameters to verify include Assay (98.0% - 102.0%), Specific Optical Rotation, Water Content (max 4.0%), and Heavy Metals (max 10 ppm). For injectable grades, the Bacterial Endotoxins level must be strictly controlled to meet sterile injectable requirements.