Our electrospray ionization-ion funnel-rf hexapole (ESI-IF-6P) source is designed to produce ions for threshold collision-induced dissociation (TCID) studies in a guided ion beam mass spectrometer. This ion source forms an initial distribution of Ca²⁺(H₂O) _x ions where x is 6–9. A new in-source fragmentation technique within the hexapole ion guide of the source is described, which is easy to implement and of modest machining and electrical costs, and is able to generate smaller Ca²⁺(H₂O) _x complexes, where x=2–5. Fragmentation is achieved by biasing an assembly of six 0.25 in. long electrodes that are inserted between the hexapole rods. The assembly is positioned in the high-pressure region of the source such that newly formed Ca²⁺(H₂O) _x ions undergo enough collisions to become thermalized, as verified by TCID studies. From the initial distribution of ions, fragmentation proceeds along the lowest energy pathway, which corresponds to sequential water loss for most complexes. However, the Ca²⁺(H₂O) complex cannot be formed using this method because charge separation into CaOH⁺ and H₃O⁺ becomes the lowest energy pathway from the Ca²⁺(H₂O)₂ complex. Therefore, this fragmentation technique can be used to identify the critical size complex for M²⁺(H₂O) _x systems, which we define as the complex size (x) at which charge separation becomes a lower energy pathway compared with simple ligand loss.

我们的电喷雾电离-离子漏斗-rf 六极杆 (ESI-IF-6P) 源设计用于在引导离子束质谱仪中产生用于阈值碰撞诱导解离 (TCID) 研究的离子。该离子源形成 Ca ²⁺ (H ₂ O) _x离子的初始分布，其中x为 6–9。描述了一种新的源内六极离子导向器内的源内碎裂技术，该技术易于实施且加工和电力成本适中，并且能够生成更小的 Ca ²⁺ (H ₂ O) _x复合物，其中x =2–5。通过偏置插入六极杆之间的六个 0.25 英寸长电极的组件来实现碎片化。该组件位于源的高压区域，使得新形成的 Ca ²⁺ (H ₂ O) _x离子经受足够多的碰撞以变得热化，正如 TCID 研究所证实的那样。从离子的初始分布开始，碎片沿着最低能量路径进行，这对应于大多数复合物的连续失水。然而，使用这种方法无法形成Ca ²⁺ (H ₂ O) 复合物，因为电荷分离成 CaOH ⁺和 H ₃ O ⁺成为来自 Ca 的最低能量途径 ²⁺ (H ₂ O) ₂络合物。因此，这种碎裂技术可用于识别 M ²⁺ (H ₂ O) _x系统的临界尺寸复合物，我们将其定义为与简单配体损失相比，电荷分离成为较低能量途径的复合物尺寸 ( x ) .