MALDITOF

MALDI-TOF, short for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, is an analytical technique used to measure the mass-to-charge ratio of ionized molecules. It is widely applied to biomolecules, especially proteins and peptides, and has become a common tool in clinical and research laboratories.

In MALDI-TOF, a sample is co-crystallized with a matrix compound that absorbs ultraviolet laser light. A pulsed laser irradiates the matrix, causing desorption and ionization of analyte molecules with minimal fragmentation. The ions are then accelerated into a time-of-flight analyzer, where their flight times are converted into mass-to-charge ratios. Most MALDI-TOF analyses use singly charged ions, and the technique is known for producing simple, highly reproducible mass spectra that reflect a characteristic fingerprint of the analyte.

Instrumentation typically includes a laser, a matrix, an ion source, a high-vacuum flight tube, and a detector. The reflectron variant improves mass resolution by correcting for kinetic energy spread among ions. Measurements are often conducted in positive ion mode, with calibration performed using standard compounds to achieve accurate m/z determination. The common mass range for protein analysis is approximately 2,000 to 20,000 Da, though extensions exist for larger molecules.

MALDI-TOF has had a major impact on microbial identification, enabling rapid, cost-effective profiling of bacteria and fungi through comparison of spectral fingerprints against reference databases. It is also used in proteomics for quick protein mass profiling and in other fields such as polymer chemistry. Limitations include dependence on high-quality reference databases, variability due to sample preparation, and challenges with certain analyte classes or complex mixtures.