The efficiency of conversion of precursor ions to observable products for electron detachment dissociation (EDD) was measured as a function of the key experimental parameters to determine their optimal values for the Fourier transform mass spectrometry analysis of anionic glycosaminoglycan carbohydrates. These parameters include electron current, electron energy, dispenser cathode heater current, electron beam duration, charge state of the precursor ion, oligomer length, and precursor ion number accumulated in an external radio frequency multipole trap. Precursor conversion is most efficient at an electron current of 15 µA, and decreases at higher and lower values. The conversion of precursor to product ions increases in efficiency as the electron pulse duration is increased. Together, these data suggest that a radially repulsive electric field is produced between the electron beam and negative ions during EDD which causes the reaction cross section to decrease at higher values of electron current (>15 µA). Elevating the heater current of the dispenser cathode increases the electron flux, but also causes ion activation, presumably by blackbody infrared irradiation. An electronic circuit is described that allows the electron current produced by the dispenser cathode to be measured during an EDD or electron capture dissociation (ECD) experiment.

中文翻译：

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评价控制电子脱离解离的实验参数，及其对糖胺聚糖裂解效率的影响

将前体离子转化为电子脱离解离 (EDD) 的可观察产物的效率作为关键实验参数的函数进行测量，以确定它们用于阴离子糖胺聚糖碳水化合物的傅里叶变换质谱分析的最佳值。这些参数包括电子电流、电子能量、分配器阴极加热器电流、电子束持续时间、前体离子的电荷状态、低聚物长度和在外部射频多极阱中累积的前体离子数。前体转换在电子电流为 15 µA 时最有效，并且在更高和更低的值时降低。随着电子脉冲持续时间的增加，前体到产物离子的转化效率增加。一起，这些数据表明，在 EDD 期间，电子束和负离子之间会产生径向排斥电场，这会导致反应截面在电子电流值较高 (>15 µA) 时减小。提高分配器阴极的加热器电流会增加电子通量，但也会引起离子激活，这可能是由黑体红外辐射引起的。描述了一种电子电路，其允许在 EDD 或电子捕获解离 (ECD) 实验期间测量分配器阴极产生的电子电流。推测是通过黑体红外辐射。描述了一种电子电路，其允许在 EDD 或电子捕获解离 (ECD) 实验期间测量分配器阴极产生的电子电流。推测是通过黑体红外辐射。描述了一种电子电路，其允许在 EDD 或电子捕获解离 (ECD) 实验期间测量分配器阴极产生的电子电流。