Ion Mobility Spectrometry CCS Measurement via Proportionality Coefficient
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current ion mobility spectrometry (IMS) methods for measuring collision cross section (CCS) are time-consuming, requiring multiple experiments at different drift voltages, which is not compatible with the fast time scale of modern chromatography techniques.
Innovation Solution
A method that calculates the CCS of a sample ion by measuring its total drift time through an ion mobility spectrometry drift cell and using a proportionality coefficient related to the external drift time in a mobility-dominated region outside the drift cell, allowing for CCS calculation in a single experiment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple experiments at different drift voltages are performed to measure CCS, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The patent applies preliminary action by performing a single calibration experiment at one drift voltage to establish the proportionality relationship between drift time and CCS. This preliminary calibration enables subsequent CCS measurements to be performed rapidly at any drift voltage without repeating the full multi-voltage experiment, thus resolving the contradiction between precision and time by investing time once in advance.
Solution Approach 2:
The patent utilizes parameter changes by varying the drift voltage dynamically during ion transmission while maintaining a linear relationship between drift time and CCS. By changing the electric field parameter and compensating through the established proportionality coefficient, the system achieves accurate CCS measurements without requiring multiple static voltage experiments, thereby reducing measurement time while preserving precision.
2Measurement precision
If multiple experiments at different drift voltages are performed to measure CCS, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent performs a preliminary calibration experiment to establish the proportionality coefficient that relates drift time to CCS at different voltages. This one-time preliminary action enables subsequent high-speed CCS measurements without repeating multi-voltage experiments, thereby improving productivity while maintaining the precision benefits of voltage variation through the use of the pre-determined proportionality relationship.
Solution Approach 2:
The patent enables continuous CCS measurements by establishing a proportional relationship that allows drift time data collected at any drift voltage to be converted to CCS values using the pre-determined proportionality coefficient. This continuous measurement capability eliminates the need to stop and perform separate experiments at different voltages, thereby maintaining productivity while ensuring measurement precision through the validated proportional relationship.
3Measurement precision
If drift time measurement includes external drift time outside the drift cell, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary proportionality coefficient that mediates between the drift time measurement (which includes external drift time) and the CCS calculation. This proportionality coefficient, determined through calibration, absorbs the complexity of accounting for external drift time contributions, allowing accurate CCS measurements without requiring direct measurement or control of external drift components, thus avoiding increased device complexity.
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 significantly reduces the measurement time for CCS, making it compatible with the time scale of chromatographic separations and improving analysis speed, with experimental errors below 1% as demonstrated in examples.
Implementation Method 1
ions become separated in time as they travel through a drift cell (drift tube) of known length containing a buffer gas (drift gas) of known composition... ions become separated based on their different collision cross sections (CCSs), which can be correlated to their differing mobilities through the buffer gas
Implementation Method 2
While the electric field moves the ions through the drift cell, the ions experience a drag force due to collisions with the stationary buffer gas molecules in the drift cell. The drag force acts against the electrical force that moves the ions.
Implementation Method 3
the drag force experienced by an ion depends on its collision cross section (CCS or Ω), which is a function of the size and shape of the ion, and on its electrical charge and mass... the electrical force that moves the ions
Implementation Method 4
In low-field drift-time IMS techniques, ions travel through the drift cell under the influence of a uniform DC voltage gradient established by electrodes of the drift cell... the ions start moving with constant drift velocity Vd, which is proportional to the applied electric field of strength E
Data Source
AI summary
The collision cross section (CCS) of a sample ion may be calculated by measuring a total drift time taken by the sample ion to travel through an ion mobility spectrometry drift cell to an ion detector. The CCS may be calculated based on the total drift time measured, and on a proportionality coefficient that defines the time taken by the sample ion to travel through a mobility dominated region between the drift cell and the detector. The proportionality coefficient may be determined from measuring the total drift times of reference ions. Calculation of the CCS of the sample ion may also be based on a proportionality coefficient that defines the time taken by the sample ion to travel through a mobility-independent region where the velocity of the ion depends on the electrostatic field strength, mass and the charge state of the ion.