If the content determination and impurities test are to be done with normalization method simultaneously , the linear range should be - 20 % of the provided limit of impurity to + 20 % of the provided limit of content 若含量测定与杂质检查同时测定,用百分归一化法,则线性范围应为杂质规定限度的- 20 %至含量限度的20 % 。