英语翻译

题目

英语翻译
The molecular weight were determined through LC/MS analysis used in the negative ion mode,where a signal located at m/z:619 a.m.u.and corresponding to [M–H]- was observed for the four derivatives and probably consisted of two catechin units linked through a CH–CHO group as shown in Fig.3.
主要不知道where a signal located at m/z:619 a.m.u.这句应该如何翻译.

答案

通过分子量分别测定了LC / MS分析用于负离子模式,在那里一个信号位于m / z:619 a.m.u.和相应的[M-H]-进行了观察研究的四个衍生品和可能包括两儿茶素单位通过CH-CHO集团有关,如图3所示.
那里的一个信号位于m / z:619 a.m.u.