The statistical properties of raw and preprocessed ToF mass spectra

Abstract

Single-valued summaries, such as signal-to-noise ratio, are insufficient to fully describe the input and output characteristics of time-of-flight mass spectra preprocessing methods. A detailed understanding of uncertainty, biases and correlations is essential for selecting appropriate methods, and for drawing confident scientific conclusions from preprocessed data. We apply a range of diagnostic tests to mass spectra, allowing statistical and systematic sources of uncertainty to be assessed throughout the typical stages of a preprocessing pipeline. Baseline correction, alignment and peak detection are reconsidered, with an emphasis on producing outputs with statistical properties compatible with an independent Poisson ion counting process. Benchmarking is also performed against a range of alternative preprocessing methods. In contrast to other preprocessing methods, new techniques are presented which provide improved statistical stability. The benefits are demonstrated using simulation and also data from the RELAX (refrigerator-enhanced laser analyser for xenon) mass spectrometer. A twofold improvement in accuracy of Xe peak measurement over the original method for the same dataset is observed.