Segmented RF Ion Guide for Mass Spectrometer
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Solution Overview
Problem
Conventional tandem mass spectrometers face inefficiencies in ion transmission due to scattering of parent and fragment ions within the collision cell, particularly for ions with low or high mass-to-charge ratios, leading to reduced sensitivity and overlapping optimal RF voltage ranges for different ion groups.
Innovation Solution
A mass spectrometer design with multiple segments of RF ion guides, each with distinct AC or RF voltage settings, optimized for both parent and fragment ions, to enhance radial confinement and transmission efficiency across varying mass-to-charge ratios, using separate or adjustable AC or RF generators and attenuators to tailor voltages and frequencies along the ion guide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single RF voltage is applied to the ion guide, then the structure is simple, but the transmission efficiency for both parent and fragment ions cannot be optimized simultaneously
Solution Approach 1:
The ion guide is divided into multiple segments along the ion beam path, with each segment independently supplied with RF voltage. This allows different RF voltage parameters to be applied to different segments, enabling optimized transmission for both parent ions (in early segments) and fragment ions (in later segments) simultaneously
Solution Approach 2:
Different segments of the ion guide are assigned different RF voltage characteristics (amplitude, frequency) tailored to the specific needs of ions at different stages. Parent ions require higher RF voltages for radial confinement during collision, while fragment ions benefit from lower RF voltages, creating local optimization throughout the guide
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the transmission efficiency of both parent and fragment ions by optimizing radial confinement and reducing ion loss, ensuring high sensitivity across a broader range of mass-to-charge ratios and kinetic energies.
Implementation Method 1
An RF voltage is applied between neighbouring electrodes. The resulting radial RF electric field is weakest along the central axis and hence ions which are scattered as a result of ion-molecule collisions will tend to be re-directed back to the central axis of the RF ion guide.
Implementation Method 2
the background gas pressure is sufficient to cause a significant number of ion-molecule collisions
Data Source
Figure 1~2
Figure 3~4
AI summary
A collision or fragmentation cell (4) is disclosed comprising a plurality of electrodes wherein a first RF voltage (7a) is applied to an upstream group of electrodes and a second different RF voltage (7b) is applied to a downstream group of electrodes. The radial confinement of parent ions entering the collision or fragmentation cell (4) is optimised by the first RF voltage applied to the upstream group of electrodes and the radial confinement of daughter or fragment ions produced within the collision or fragmentation cell (4) is optimised by the second different RF voltage applied to the downstream group of electrodes.