Ion lenses, vertical ion introduction and efficient ion transport

After leaving the ionisation source, ions must be efficiently collected and guided into the mass analyser; this function is performed by the ion optical system. An ion lens is a component comprising a set of metal electrodes with different potentials; it uses an electrostatic field to focus and collimate the diverging ion beam, thereby reducing ion loss during transmission. The Xinceyuan ProC series employs ‘high-transmission-efficiency ion lens technology’, combined with a proprietary titanium alloy ion transfer tube, with the aim of delivering more ions into the analyser. This directly enhances the overall sensitivity of the instrument, enabling the quantitative detection of analytes at ppb concentrations in ambient air.

Orthogonal ion introduction is another key design feature. In dual-field reflection time-of-flight mass spectrometry, when ions generated by the ionisation source travel directly into the analyser along their original direction, their initial kinetic energy causes dispersion, leading to a reduction in resolution. Vertical introduction technology allows ions to be introduced into the flight tube at an approximately perpendicular angle; after being ‘shaped’ by the electric field, they are accelerated axially, resulting in a more concentrated temporal and spatial distribution of ions at the entrance, thereby significantly improving mass resolution. The NewCeyuan ProC-1/ProC-1C/ProC-1S models are all specified as utilising “ion vertical introduction technology with a dual-field reflection time-of-flight mass spectrometer as the mass analyser”; it is precisely this combination that delivers a mass resolution superior to 3500.

The ion transfer tube itself is also a key consideration. The MSI DPI utilises a proprietary titanium alloy ion transfer tube, with the front end polished to prevent damage to the sample surface; it is also removable for cleaning and maintenance. During imaging, ions generated by desorption and photoionisation enter the main instrument via this tube, and the transfer efficiency directly affects the imaging signal-to-noise ratio and spatial resolution. The MSI LDPI similarly relies on efficient ion transport, delivering neutral molecules desorbed by the laser to the main instrument following post-laser photochemical ionisation.

In short, the ion lens is responsible for ‘focusing’, the vertical introduction system for ‘alignment’, and the transport tube for ‘delivery’; together, these three factors determine the number and accuracy of ions that ultimately reach the analyser and are detected. No matter how powerful the front-end ionisation may be, if a significant number of ions are lost during transmission, sensitivity and imaging quality will still be severely compromised—which is precisely why New Source emphasises both ion lenses and titanium alloy transmission tubes in several of its products. MSI DPI and MSI LDPI are compatible with Agilent, AB SCIEX and Thermo mass spectrometers.