Quadrupole Mass Filter Broad Mode Contamination Reduction
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Solution Overview
Problem
Mass filters in mass spectrometry, particularly quadrupole mass filters, experience contamination issues leading to charging effects and sensitivity loss, especially in extreme applications like proteomics, requiring frequent cleaning and resulting in instrument downtime.
Innovation Solution
Operating the mass filter in a broad mass range or substantially non-m/z filtering mode during idle periods when the discontinuous ion optical device is not processing ions, reducing ion deposition on the filter surfaces and minimizing charging effects by using a substantially RF-only mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the mass filter operates in m/z filtering mode to transmit selected ion ranges, then the desired mass separation and analysis function is achieved, but ion deposition on rod surfaces accumulates causing contamination and charging effects
Solution Approach 1:
The patent applies periodic action by alternating between m/z filtering mode and broad mass range mode in cyclic intervals. During broad mass range mode periods, ions of all masses are transmitted to prevent surface contamination accumulation, while during m/z filtering mode periods, precise mass separation is performed. This periodic switching resolves the contradiction by periodically clearing potential contamination before it reaches critical levels that would compromise sensitivity.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the voltage parameters applied to the quadrupole rods. In m/z filtering mode, specific DC and RF voltage combinations are applied to achieve precise mass selection. In broad mass range mode, the voltage parameters are changed to transmit all ion masses. This parameter switching enables the system to alternate between high-precision analysis and contamination-prevention states.
2Productivity
If the mass filter transmits ions continuously in m/z filtering mode, then analysis productivity is maintained, but contamination builds up requiring frequent cleaning and causing downtime
Solution Approach 1:
The system implements periodic action by introducing brief intervals of broad mass range mode operation during which contamination is reduced. These periodic interruptions are strategically timed and kept sufficiently short that overall analysis productivity is maintained, while preventing the accumulation of contamination that would lead to extended cleaning downtime.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that even during broad mass range mode periods, ions are still transmitted through the system, just without the strict mass filtering. This keeps the ion source and downstream detectors actively engaged and prevents complete operational interruption, thereby maintaining productivity while achieving contamination control.
3Measurement precision
If the mass filter uses narrow isolation range for precursor ions, then specific protein analysis precision is improved, but ion deposition rate increases causing faster sensitivity loss
Solution Approach 1:
The patent applies periodic action by alternating narrow isolation range filtering with broad mass range transmission. During narrow isolation periods, high protein identification accuracy is achieved. During broad mass range periods, the transmission of diverse ion masses prevents localized ion deposition that would occur with continuous narrow filtering, thereby extending the cleaning interval despite intensive protein analysis.
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 contamination, extending the interval between cleaning operations and maintaining instrument sensitivity, with a demonstrated extension of cleaning cycles by a factor of 2 or more in extreme applications.
Implementation Method 1
an RF voltage, superimposed by a DC voltage, is applied between the two rod pairs
Implementation Method 2
A selected m/z range of interest is stable within the quadrupole and will be transmitted through it
Implementation Method 3
Some ions hitting a surface of the rods can stick to that surface
Implementation Method 4
Ions that stick to the surface can thereby modify the work function of the material of the surface and can form insulating layers which are prone to charging effects
Data Source
AI summary
Disclosed herein is a mass spectrometry method having steps of: transmitting ions from an ion source through a mass filter; processing ions received from the mass filter in a discontinuous ion optical device downstream of the mass filter; operating the mass filter for a plurality of periods in a mass/charge ratio (m/z) filtering mode to transmit ions in one or more selected ranges of m/z to the discontinuous ion optical device; and operating the mass filter in a broad mass range mode transmitting ions of a mass range substantially wider than any mass range transmitted in the m/z filtering mode during one or more periods in which the discontinuous ion optical device is not processing ions from the mass filter. Utilization of this method assists to reduce contamination in the mass filter.