Ion Trap Mass Analyzer Quantitative Analysis
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Solution Overview
Problem
Conventional methods of quantitative mass analysis using ion trap mass spectrometers introduce inaccuracies due to fluctuations in the ionization process, leading to higher relative standard deviation (RSD) and uncertainty in measurements, as they require separate ion injection events for analytes and internal standards.
Innovation Solution
A method and system for quantitative mass analysis in an ion trap mass analyzer where both analyte and internal standard precursor ions are injected and analyzed in a single ion injection event, with specific m/z isolation and fragmentation techniques to generate product ions, allowing for simultaneous acquisition of mass spectra with minimal ionization fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate ion injection events are used for analyte and internal standard, then the ion trap can analyze each species individually, but measurement precision deteriorates due to ionization process fluctuations between events
Solution Approach 1:
The patent combines the injection of analyte ions and internal standard ions into a single common ion injection event, allowing both species to be introduced simultaneously into the ion trap. This merging eliminates the variability introduced by separate ionization events and enables direct comparison of ion signals, thereby improving measurement precision and reducing quantification uncertainty.
Solution Approach 2:
The patent segments the analysis process by first isolating analyte ions within a specific m/z range, then isolating internal standard ions within a different m/z range, both from the same injected ion population. This segmentation allows selective fragmentation and analysis of each species while maintaining the benefit of simultaneous injection, resolving the contradiction between individual analysis and measurement precision.
2Measurement precision
If multiple precursor ions of different m/z ratios are injected in a single event, then ionization consistency improves, but device complexity increases due to need for selective isolation and fragmentation
Solution Approach 1:
The patent employs dynamic control of the ion trap's radio-frequency (RF) trapping voltage amplitude to achieve selective isolation and fragmentation. By dynamically adjusting the RF amplitude to specific values during different time periods, the system can selectively trap or eject ions of specific m/z ranges, and control fragmentation of selected precursor ions. This dynamic control enables complex selective analysis from a single injected ion population without requiring physically complex additional hardware.
3Measurement precision
If RF amplitude is varied for m/z analysis scan, then product ions can be detected, but analyte and internal standard ions may be ejected or dissociated prematurely
Solution Approach 1:
The patent performs preliminary m/z isolation of both analyte and internal standard precursor ions before initiating the RF amplitude variation for product ion detection. By first selecting and trapping only the desired precursor ions within specific m/z ranges, the system ensures that when RF amplitude is subsequently varied for fragmentation and product ion analysis, only the intended precursor ions are present to undergo these processes. This preliminary isolation action prevents premature ejection or dissociation of unwanted ions.
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 minimizes errors and improves measurement uncertainty by allowing for precise quantification of analytes with reduced RSD, utilizing a single ion injection event and advanced fragmentation techniques to isolate and analyze precursor ions of different m/z ratios.
Implementation Method 1
the amplitude of the radio-frequency (RF) trapping voltage applied to the ion trap electrodes
Implementation Method 2
The ions may be fragmented using ion trap type collision-induced dissociation (IT CID). Using a first IT CID step, a first excitation waveform voltage with one or more frequency components may be applied to the ion trap electrodes to produce a corresponding first excitation waveform field superposed on the ion confinement field or fields of the ion trap. This first excitation waveform field couples to a frequency component of the unforced or natural oscillatory motion of the first precursor ions in the trapping field, causing the first precursor ions to pick up kinetic energy from the excitation waveform field and undergo energetic collisions with molecules of a background gas causing dissociation of the first precursor ions to produce first product ions.
Data Source
AI summary
A method of quantitative mass analysis of precursor species of different mass-to-charge (m/z) ratios from a single or the same ion injection event is disclosed. A plurality of precursor ion species having different respective m/z ratios are introduced into a mass spectrometer at the same time. The precursor ion species are isolated. A first subset of the isolated precursor ions having a first m/z ratio is fragmented and analyzed. A second subset of the isolated precursor ions having a second m/z ratio is fragmented and analyzed. A first mass spectrum is generated for the fragment ions of the first subset of precursor ions, and a second mass spectrum is generated for the fragment ions of the second subset of precursor ions.