Reference substance: a reference substance used for identification, inspection, content determination and calibration of instrument performance; reference substance is reviewed and approved by the national drug control agency, and its standard should not be lower than the quality standard of the product.

Standard substance: a standard substance used for bioassay, determination of content or potency in antibiotics or biological drugs, expressed in potency unit (U).

Reference substance and standard substance are two different concepts, which have been clearly defined in the Chinese Pharmacopoeia: reference substance refers to the reference substance used for identification, inspection, content determination and calibration of the performance of the verification instrument. Standard substance: a standard substance used for bioassay, determination of content or potency in antibiotics or biological drugs, expressed in potency unit (U). In the literature, the two concepts are often confused, thinking that the reference substance is the standard substance, and it is only one substance and two formulations. The reason for the error may be that some medicines have both the reference substance and the standard substance.

For example: when cefaclor titer is determined by microbiological method, use cefaclor standard, when using HPLC or UV method, use reference substance; when phenacetin is used as a melting point calibration substance, use melting point standard, When determining the content, use the reference substance. Even the standards and controls of the same substance may have different specifications, calibration methods and uses.