MALDI Mass Spectra Acquisition via Laser Energy Stepwise Adjustment
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Solution Overview
Problem
Current MALDI time-of-flight mass spectrometry techniques face challenges in achieving high concentration accuracy and reproducibility of ion signals, particularly in analyzing mixtures, due to signal saturation and limited dynamic range, which affects the identification of microbial species in complex samples.
Innovation Solution
The technique involves a step-wise increase in energy density in the laser spot, replacing saturated signals with extrapolations from lower energy density spectra and optionally defocusing the ion beam to prevent saturation, allowing for improved dynamic range and reproducibility by determining the rise factors of ion signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the laser energy density is increased to improve ion signal intensity, then the ion signal strength increases, but signal saturation occurs limiting the dynamic measuring range
Solution Approach 1:
The patent applies dynamic adjustment of laser energy density by acquiring multiple mass spectra at different energy density levels. The system dynamically selects and combines spectra from optimal energy density levels to prevent saturation while maintaining high ion signal intensity for accurate measurement.
Solution Approach 2:
The patent segments the ion signal measurement process by acquiring multiple mass spectra at different laser energy density levels. Each spectrum captures a different portion of the dynamic range, and these segmented measurements are subsequently combined to reconstruct the complete signal without saturation effects.
2Measurement precision
If multiple individual time-of-flight spectra are summed to increase dynamic measuring range, then the dynamic range increases, but the number of measurements required increases time consumption
Solution Approach 1:
The patent changes the parameter of laser energy density across multiple measurements to optimize signal capture. By varying energy density rather than simply increasing the number of summed spectra, the method achieves extended dynamic range more efficiently, reducing the total number of measurements and time consumption.
3Measurement precision
If the ion beam is focused to increase ion signal intensity, then measurement sensitivity improves, but signal saturation occurs more readily
Solution Approach 1:
The patent applies dynamic adjustment of ion beam focusing by acquiring mass spectra at different focus levels corresponding to different energy density levels. This dynamic approach allows the system to operate at optimal focus settings for each measurement condition, maintaining high sensitivity while avoiding saturation through subsequent data processing.
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 enhances the dynamic measuring range and concentration accuracy of mass spectra, enabling better detection of low-proton affinity analytes and reducing sample consumption, while providing additional information on proton affinities, thus improving the analysis of complex mixtures.
Implementation Method 1
ionization of the analyte substances by matrix assisted laser desorption
Implementation Method 2
the electrical currents created at the ion detector by the ions after they have passed through the flight path
Implementation Method 3
the electrical currents created at the ion detector by the ions after they have passed through the flight path are first amplified by secondary electron multipliers
Data Source
AI summary
The invention relates to acquisition techniques for time-of-flight mass spectra with ionization of the analyte substances by matrix assisted laser desorption. Generally speaking, these acquisition techniques involve adding together a large number of individual time-of-flight spectra, each with restricted dynamic measuring range, to form a sum spectrum. The invention provides a method that improves, in particular, the reproducibility, the concentration accuracy and therefore the ability to quantify the mass spectra. Particular embodiments also increase the dynamic range of measurement. For this purpose, multiple series of mass spectra are acquired, whereby the energy density in the laser spot is increased in discrete steps. As a result, many ion signals saturate the detector and can therefore no longer be evaluated. However, it is possible to employ a technique in which the ion beam is increasingly defocused, or, secondly, to replace parts of the spectrum that are subject to saturation by intensity extrapolations from mass spectra acquired with lower energy density. In the first case, hundreds or thousands of individual mass spectra must be added together in order to increase the dynamic measuring range. In the second case, the finally acquired mass spectrum, with its replacements, forms a mass spectrum with a high dynamic measuring range, improved reproducibility and better concentration accuracy. The gradient of the increasing intensities of the ion signals, as a function of the energy density, supplies additional information about the proton affinity of the analyte ions. The concentration accuracy is enhanced because the increase in the number of proton donors in the ionization plasma leads to an increase in the ionization of those analyte substances that have a lower proton affinity.