Quadrupole Mass Filter Ion Selection for ToF Spectrometer
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Solution Overview
Problem
Mass spectrometers face issues with 'wrap around' and detector saturation due to high m/z species contaminating the spectrum and consuming detection capacity when operating in orthogonal time-of-flight mode, especially when the mass range of interest is narrower than the ion beam's mass range.
Innovation Solution
Adjusting the RF and DC voltages applied to the quadrupole mass filter based on a stability diagram to filter out ions outside the range of interest, and overpulsing the ToF extraction to increase duty cycle, while fragmenting ions inside the range of interest in the collision cell to improve spectral analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ToF repetition rate is set high to record the mass range of interest, then the recording capability for the mass range of interest is improved, but high m/z species arrive in following extractions causing wrap around contamination
Solution Approach 1:
The patent extracts and removes high m/z ions from the ion beam using a quadrupole mass filter before they enter the ToF detector. This prevents these ions from causing wrap-around contamination in subsequent extractions, allowing high ToF repetition rates to be used without spectral contamination.
Solution Approach 2:
The patent applies preliminary mass filtering using the quadrupole mass filter to remove unwanted high m/z ions before the ions enter the ToF detection region. This preliminary action prevents the wrap-around problem from occurring in the first place, enabling accurate spectral recording at high repetition rates.
2Quantity of substance
If high m/z species are present in the ion beam, then the ion population is complete, but detector saturation occurs and detector lifetime is shortened
Solution Approach 1:
The quadrupole mass filter extracts and removes high m/z ions that would otherwise saturate the detector and reduce its lifetime. This selective extraction maintains a manageable ion population at the detector while preserving the ability to analyze the complete ion population through controlled sampling.
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
Effectively filters out ions outside the range of interest, reducing wrap around and detector saturation, enhancing the accuracy and longevity of the mass spectrometer by controlling the low and high mass boundaries and increasing the duty cycle of the mass spectrometer.
Implementation Method 1
operating a quadrupole mass filter in a bandpass mode such that ions outside of a range of interest are filtered from the ion beam, leaving ions inside the range of interest in the ion beam
Implementation Method 2
analyzing the ions by time of flight to produce an ion spectrum
Implementation Method 3
fragmenting the ions inside the range of interest in the ion beam, via the collision cell
Data Source
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AI summary
A method and mass spectrometer for filtering ions are provided. The mass spectrometer generally comprises an ion guide, a quadrupole mass filter, a collision cell and a time of flight (ToF) detector, and is enabled to transmit an ion beam through to the ToF detector. The mass spectrometer is operated in MS mode, such that ions in the ion beam remain substantially unfragmented, the quadrupole mass filter operating at a pressure substantially lower than in either of the ion guide and the collision cell. The quadrupole mass filter is operated in a bandpass mode such that ions outside of a range of interest are filtered from the ion beam, leaving ions inside the range of interest in the ion beam. The ions inside the range of interest are analyzed at the ToF detector.