二楼解释得很清楚。
原文也说得很明白: Working solutions (0.1 and 4 mmolL-1) were prepared daily by appropriate dilution of the stock solutions. 两种工作液Working solutions (0.1 and 4 mmolL-1)是将stock solutions(贮备液或母液)适当稀释 were prepared daily(每天) by appropriate dilution 即可得到。