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Mass Spectrometry


Perseptive Biosystems(ABI) - Voyager-DE RP - MALDI-TOF mass spectrometer is equipped with Delayed Extraction technology (DE), which provides improved resolution, sensitivity, and mass accuracy. It is capable of analyzing the intact mass of peptides, proteins*, oligonucleotides, polymers, and small molecules.

* For protein identification please visit our Mass Mapping service page.

MALDI-TOF (Matrix Assisted Laser Desorption Ionization - Time of Flight) is a soft ionization technique used to determine the intact mass of biomolecules and polymers.

In MALDI, a matrix (low molecular weight UV absorbing substance) is embedded with a sample on a metal target plate. The choice of matrix depends on the properties of the molecules in the individual sample (ie protein, peptide, DNA, etc.).

The metal target plate is inserted in the mass spectrometer and an ultraviolet laser is applied to the matrix-sample spot. The matrix absorbs the laser energy, preventing the sample from being destroyed, and transfers the laser energy to the sample facilitating in the desorption and ionization of the sample.

The ionized sample and matrix molecules are accelerated by a high voltage field into an electrostatic flight tube. The Time of Flight (TOF) needed for these ionized molecules to reach the detector is a measure of the molecule's mass/charge ration (m/z).

MALDI animation

click to enlarge


The instrument is capable of measuring mass over the range of 100Da to approximately 200,000Da. However, below 500Da, the matrix ions may obscure the sample mass, and above 100,000Da, ionization is difficult. In linear mode, the instrument has an optimal working range of 500Da to 100,000Da. In reflector mode, the instrument has an optimal working range of 500Da to 4000Da.

High quality spectra can be obtained from 1uL of 100fmol-10pmol of sample loaded onto the target plate. Too much material can broaden spectral peaks, resulting in lower resolution, and in extreme cases may suppress ionization. The presence of excess salts at concentrations greater than 50mM can also cause significant ion suppression.

Mass accuracies depend on calibration of the instrument against a standard, and also upon the condition of the sample. Too much starting material, high salt content, or the presence of glycerol, detergents and urea can broaden spectral peaks, and compromise mass accuracy. Typical values when calibrating against an external mass standard for accuracy are 0.1% (1Da per 1000Da) in linear mode, and 0.01% (1Da per 10,000Da) in reflector mode.

We expect to return spectra to the investigator within 72 hours of receiving the samples.