Related substances
Carry out the method for thin-layer chromatography, Appendix III A, using a silica gel precoated plate (Merck silica gel 60 F254plates are suitable) and a mixture of 1 volume of 18M ammonia, 30 volumes of chloroform and 70 volumes of ethyl acetate as the mobile phase. Apply separately to the plate 10 μl of each of three solutions of the substance being examined in methanol containing (1) 1.0% w/v, (2) 0.01% w/v and (3) 0.005% w/v, respectively. After removal of the plate, allow it to dry in air, examine under ultraviolet light (254 nm), expose to iodine vapour for 2 hours and examine again. For each examination anysecondary spot in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) (1%) and not more than one such spot is more intense than the spot in the chromatogram obtained with solution (3) (0.5%).
最后一句的意思是超过0.5%的
杂质不得超过一个，还是溶液2中的点要比溶液3中的点要浓，作为说明从溶液·1到溶液3是呈线性的，作为类似系统适应性溶液。
IMPURITIES
A. 3-ethyl-3-(3-hydroxyphenyl)-1-methylperhydroazepin-2-one
B. 3-ethyl-1-methyl-3-phenylperhydroazepine
C. 4-(3-ethyl-1-methylperhydroazepin-3-yl)-2-[3-(3-ethyl-1-methylperhydroazepin3-yl)phenyl]phenol
D. 3,3￠-oxybis(3-ethyl-1-methylperhydroazepin-3-ylbenzene)
E. 3-ethyl-3-(3-butoxyphenyl)-1-methylperhydroazepine
标准中规定了5个已知杂质，却没有说怎么测，限度为多少，不明白怎么回事，求高手赐教
