ABSTRACT
OBJECTIVE: To discuss the problem of instrumental test method of clarity and degree of opalescence of liquids in the general notice 0902 of China Pharmacopeia(Ch.P) 2015, find out the causes and offer solutions. METHODS: The test methods of clarity in Ch.P 2015 and European Pharmacopeia (EP) 8.0 were compared, including instrumental types, applicability, sample requirements, and result evaluation. RESULTS: The primary opalescent suspension for the instrumental method is the same as the visual method, using the absorbance (A=0.12-0.15) at 550 nm to control the opalescence. Because the resolving power of the instrumental method is far higher than the visual method, the limit becomes interval distribution instead of simple point. The opalescent value (NTU) of the upper limit (A=0.15) is about 1.35 times of the lower limit (A=0.12). When the NTU value of the test liquid is in this interval, the result evaluation will be hard. CONCLUSION: The preparation of the primary opalescent suspension in Ch.P 2015 is different from EP8.0. For this reason, the limit set by Ch.P 2015 is actually stricter than that of EP8.0. The opalescent value of the standard solution used by Ch.P 2015 is about 75% of that used by EP8.0.