Critical factors determining the quantification capability of matrix-assisted laser desorption/ionization– time-of-flight mass spectrometry

Abstract

Quantitative analysis with mass spectrometry (MS) is important but challenging. Matrix-assisted laser desorption/ionization (MALDI) coupled with time-of-flight (TOF) MS offers superior sensitivity, resolution and speed, but such techniques have numerous disadvantages that hinder quantitative analyses. This review summarizes essential obstacles to analyte quantification with MALDI-TOF MS, including the complex ionization mechanism of MALDI, sensitive characteristics of the applied electric fields and the mass-dependent detection efficiency of ion detectors. General quantitative ionization and desorption interpretations of ion production are described. Important instrument parameters and available methods of MALDI-TOF MS used for quantitative analysis are also reviewed.This article is part of the themed issue 'Quantitative mass spectrometry'.

Rapid glycosyl‐inositol‐phospho‐ceramide fingerprint from filamentous fungal pathogens using the MALDI Biotyper Sirius system

“…In addition, that range was used to avoid poor co-crystallization with the matrix which can lead to a viscous spot on the MALDI target plate precluding any transfer of energy from the laser to the matrix that enables the desorption of the molecules of interest. 35,36 In addition to optimizing the dilution of the sample, we also tested various solvent mixtures (chloroform, methanol and combinations of those) to solubilize the matrix in order to generate high-quality and reproducible mass spectra. After numerous iterations of optimization, the matrix solvent composed of chloroform and methanol at a ratio 9 to 1 gave mass spectra with a signal-to-noise ratio greater than 10 (Figure 1).…”

“…We found that a sample diluted at a McFarland of 20 to 50 in double‐distilled water was most appropriate for our experiments as it gave spectra with the highest signal‐to‐noise ratio (>10) and mass resolution (>200) (Figure 1). In addition, that range was used to avoid poor co‐crystallization with the matrix which can lead to a viscous spot on the MALDI target plate precluding any transfer of energy from the laser to the matrix that enables the desorption of the molecules of interest 35,36 . In addition to optimizing the dilution of the sample, we also tested various solvent mixtures (chloroform, methanol and combinations of those) to solubilize the matrix in order to generate high‐quality and reproducible mass spectra.…”

Simultaneous quantification of atropine and scopolamine in infusions of herbal tea and Solanaceae plant material by matrix‐assisted laser desorption/ionization time‐of‐flight (tandem) mass spectrometry

“…Excessive analyte concentrations will reduce ionization efficacy and thus minimize relative signal increase. Furthermore, quantification by MALDI‐TOF MS might be challenging due to (i) inhomogeneous crystallization and spot‐to‐spot variability causing sweet spots of maximum signal intensity in neighborhood to areas of insufficient analyte concentrations, (ii) less reproducible geometry of matrix spots causing laser shots to miss the targets, (iii) ablation of matrix‐analyte crystals before the total number of preset laser shots has been released, and (iv) ion suppression evoked by non‐analyte molecules present in a complex sample …”

The Reliable, Automatic Classification of Neonates in First-Tier MALDI-MS Screening for Sickle Cell Disease

“…Quantitative analysis with MALDI-TOF MS was initially viewed as implausible and inherently irreproducible because the mass spectrum’s signal intensity varies as a function of the sample’s composition, the sample’s morphology, the laser conditions, and sample depletion during continuous laser exposure [ 1 , 2 ]. Inhomogeneous sample deposition is also a crucial obstacle, and leads to poor signal reproducibility (including the so-called “sweet spot” and “coffee-ring” effects) [ 3 , 4 ].…”