OBJECTIVE: To establish the method for the determination of 4 residual organic solvents in finasteride raw materials, i.e. methanol, acetone, chloroform and methylbenzene. METHODS: Headspace gas chromatography was adopted. The residual organic solvents were separated on Phenomenex ZB-624 capillary column using dimethyl sulfoxide as solvent by temperature programming. FID was used as detector with a temperature of 250 ℃. The inlet temperature was 200 ℃. N2 was used as carrier gas with split ratio of 5 ∶ 1. With headspace sampling, equilibrium temperature was 80 ℃ and equilibrium time was 45 min. RESULTS: The linear ranges of methanol, acetone, chloroform and methylbenzene were 12.0-1 200, 10.0-1 000, 1.20-120 and 1.78-178 μg/ml (r=0.999 6～0.999 8), respectively. Recovery rates were 94.7%-97.5% (RSD2.1%); the detection limits were in the rang of 0.021 6 to 10.93 μg/ml. Residual amount of 4 organic solvents in 5 batches of samples were in line with the requirements of Chinese Pharmacopeia (2010 edition). CONCLUSIONS: The method is sensitive and reproducible. It can be applied for the determination of the residual organic solvents in finasteride raw materials.

This article introduces two principles and proves the circle of feasible basis can be avioded by using these principlles.

The Passage gives the method of elementary transformation of gretest common factor to solve multiple polynomidal,which is simpler than traditional division algorithm.