Mass Spectrometer Ion Signal Digitization and Dead Time Reduction
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Solution Overview
Problem
Conventional mass spectrometers using Time to Digital Converters face challenges in distinguishing between single and multiple ion arrival events, leading to distorted intensity and mass-to-charge ratio measurements, especially at high ion fluxes, and require significant data processing due to large amounts of spectral data, which is disadvantageous for real-time applications.
Innovation Solution
Employing an Analogue to Digital Converter system that digitizes ion signals with high sampling rates, processes signals to determine ion arrival times and intensities, and combines data to form a continuum mass spectrum, allowing for accurate recording of multiple ion events and reducing dead time effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a Time to Digital Converter is used to record ion arrival times, then the amount of mass spectral data is substantially reduced, but the ability to discriminate between one or multiple ions arriving at substantially the same time is lost
Solution Approach 1:
The patent combines the advantages of both TDC and ADC approaches by integrating a Time to Digital Converter with an Analogue to Digital Converter. The TDC records ion arrival times with high precision, while the ADC simultaneously records the analogue signal amplitude that contains information about the number of ions. This merging of two conversion systems allows the system to reduce data volume while preserving the ability to discriminate between single and multiple ion events.
Solution Approach 2:
The patent introduces an intermediary processing stage that takes the digital time values from the TDC and the digital amplitude values from the ADC, and combines them in a hybrid data structure. This intermediary representation allows the system to maintain both the time precision of TDC and the intensity discrimination of ADC, resolving the contradiction between data reduction and measurement precision.
2Measurement precision
If an Analogue to Digital Converter is used to record ion signals, then intensity information is preserved, but very large amounts of mass spectral data are acquired requiring large memory
Solution Approach 1:
The patent extracts only the essential information from the full ADC signal by using the TDC to identify precise ion arrival times. Instead of storing the complete analogue-to-digital converted signal for every time point, the system extracts discrete time-of-flight values and associated intensity values only at ion event occurrences. This extraction approach preserves intensity information while dramatically reducing the total data volume that requires memory storage.
3Measurement precision
If many individual spectra are histogrammed to form a final mass spectrum, then a composite mass spectrum is produced, but data processing time increases and memory requirements increase
Solution Approach 1:
The patent performs preliminary processing of ion signal data by applying correction factors to individual ion event records before they are accumulated into the final mass spectrum. By pre-correcting for detector response variations, electronic noise characteristics, and flight time deviations at the individual event level rather than waiting for complete spectrum accumulation, the system reduces the computational burden during final spectrum formation, thereby reducing data processing time while maintaining spectrum quality.
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 dynamic range and accuracy of mass spectrometry by accurately recording ion intensities and reducing noise, improving the signal-to-noise ratio and mass resolution, while minimizing data processing time and memory requirements.
Implementation Method 1
The secondary electron multiplier or discrete dynode electron multiplier generates a pulse of electrons in response to an ion arriving at the ion detector
Implementation Method 2
A Time of Flight mass analyser comprises an ion detector
Data Source
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AI summary
A method of mass spectrometry is disclosed wherein voltage signals from an ion detector are analysed. A second differential of each voltage signal is obtained and the start and end times of observed voltage peaks are determined. The intensity and average time of each voltage peak is then determined and the intensity and time values are stored. An intermediate composite mass spectrum is then formed by combining the intensity and time values which relate to each voltage peak observed from multiple experimental runs. The various pairs of time and intensity data are then integrated to produce a smooth continuum mass spectrum. The continuum mass spectrum may then be further processed by determining the second differential of the continuum mass spectrum. The start and end times of mass peaks observed in the continuum mass spectrum may be determined. The intensity and mass to charge ratio of each mass peak observed in the continuum mass spectrum may then determined. A final discrete mass spectrum comprising just of an intensity value and mass to charge ratio per species of ion may then be displayed or output.