Enhancing MALDI time-of-flight mass spectrometer performance through spectrum averaging

Area of Science:

• Analytical Chemistry
• Biophysics
• Mass Spectrometry

Background:

• Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometers are widely used for analyzing biological molecules.
• Despite their robustness, significant variability (30-50% of measurements exceeding 5 ppm error) is observed even with internal calibration.
• Increasing laser shots per spectrum does not resolve this measurement variability.

Purpose of the Study:

• To identify the source of variability in MALDI-TOF mass spectrometry measurements.
• To evaluate the contribution of the analog-to-digital (AD) detection system to measurement errors.
• To propose a method for mitigating variability in MALDI-TOF mass measurements.

Main Methods:

• Utilized a modern MALDI-TOF/TOF instrument to assess variability sources.
• Analyzed the impact of analog-to-digital converter (ADC) binning and clock speed on raw flight time data.
• Investigated the effect of automated peak fitting algorithms on calibration and mass spectra.

Main Results:

• The primary source of variability is identified as the binning of raw flight time data by the AD detection system's electronics and clock speed.
• This binning necessitates interpolation by automated peak fitting, affecting calibration and mass spectra accuracy.
• Observed variation follows a normal distribution, indicating multiple contributing factors.

Conclusions:

• Spectrum averaging of multiple independent measurements is an effective strategy to mitigate variability in MALDI-TOF mass spectrometry.
• Averaging leverages the inherent binning error of the AD detector system to improve measurement accuracy.
• This approach offers a more reliable method for accurate MALDI-TOF mass measurements compared to increasing laser shots.