In MALDI-TOF mass spectrometry, what is the first step?

In MALDI-TOF mass spectrometry, what is the first step?

• A. Ionization of molecules
• B. Mass-to-charge ratio measurement
• C. Generation of a molecular signature
• D. Calibration of the instrument

Answer: (A)

The first step is ionization of the molecules. In MALDI-TOF, the sample is mixed with a matrix and hit with a laser; the matrix absorbs the energy and transfers it to the analyte, causing desorption and ionization so that charged particles are produced. Without ionization, there are no ions to accelerate or measure, so no spectrum can be formed. After ionization, the ions are accelerated in an electric field and their time of flight is measured to determine their mass-to-charge ratios. Generating a molecular signature comes from analyzing the resulting spectrum and matching it to a database, which happens after data acquisition. Calibration helps ensure accuracy but is not the initial event that creates the detectable ions.

The first step is ionization of the molecules. In MALDI-TOF, the sample is mixed with a matrix and hit with a laser; the matrix absorbs the energy and transfers it to the analyte, causing desorption and ionization so that charged particles are produced. Without ionization, there are no ions to accelerate or measure, so no spectrum can be formed. After ionization, the ions are accelerated in an electric field and their time of flight is measured to determine their mass-to-charge ratios. Generating a molecular signature comes from analyzing the resulting spectrum and matching it to a database, which happens after data acquisition. Calibration helps ensure accuracy but is not the initial event that creates the detectable ions.