Dual Mode TOF Mass Spectrometer Reflectron Voltage Adjustment
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Solution Overview
Problem
Conventional Time of Flight mass analyzers face limitations in analyzing ions across a wide range of molecular weights due to aberrations that become more significant as the size or molecular weight of ions increases, leading to distortions and reduced spectral resolution.
Innovation Solution
The implementation of a Time of Flight mass analyzer operable in multiple modes, where ions travel different distances within the instrument depending on their size, with a reflectron system allowing ions to turn around at varying points to optimize path length for either high or low molecular weight ions, thereby reducing collisions and aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single fixed path length is used in the Time of Flight mass analyser, then the analysis of low molecular weight ions can be optimised, but the analysis of high molecular weight ions deteriorates due to increased collisions and aberrations
Solution Approach 1:
The reflectron voltage is made dynamically adjustable to change the ion turning point position along the flight path. By varying the reflectron voltage between a first voltage (for high molecular weight ions) and a second voltage (for low molecular weight ions), the system adapts the effective path length to match the specific analysis requirements, resolving the contradiction between optimising for specific mass ranges and maintaining versatility across wide mass ranges
Solution Approach 2:
The system changes the electrical parameter (reflectron voltage) to control the ion trajectory and turning point position. By adjusting this parameter, the effective path length is modified to reduce collisions for high molecular weight ions while maintaining sufficient path length for low molecular weight ion analysis, thereby improving spectral resolution across different mass ranges
2Reliability
If the distance traveled by ions is increased to reduce time of flight aberrations, then spectral quality improves for low molecular weight ions, but collisions increase for high molecular weight ions causing distortions
Solution Approach 1:
The reflectron voltage is dynamically adjusted based on the molecular weight of ions being analysed. For high molecular weight ions, the reflectron voltage is set to a higher value that causes ions to turn around at a point closer to the source, reducing the effective path length and thus reducing collisions with background gas. For low molecular weight ions, the voltage is reduced to allow longer flight paths for better spectral quality
Solution Approach 2:
The system takes preliminary action by adjusting the reflectron voltage before ion analysis to pre-determine the turning point position. This preliminary adjustment prevents excessive collisions by ensuring that high molecular weight ions do not travel unnecessarily long distances through the background gas, thereby preventing distortions before they occur
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 enhances the spectral resolution and reduces distortions by optimizing the path length for each mode, improving the analysis of both large and small ions by minimizing collisions and other sources of error, thus providing clearer mass spectra.
Implementation Method 1
by controlling one or more electric fields or potentials applied to the reflectron, it is possible to control the position at which ions turn around
Implementation Method 2
the time taken for an ion to traverse a path of known length being related to the ions' mass to charge ratio
Data Source
AI summary
Disclosed herein is an ion analysis instrument comprising a Time of Flight (“TOF”) mass analyser comprising a reflectron. The instrument is operable in at least a first mode and a second mode, wherein in said first mode ions are caused to turn around at a first point in the reflectron and wherein in said second mode ions are caused to turn around at a second point in the reflectron such that the distance traveled by ions within the Time of Flight mass analyser is greater in the second mode than the distance traveled by ions within the Time of Flight mass analyser in the first mode. In this way, the operating modes can be selectively optimised for the analysis of ions of different masses.