Mass Spectrometry

  • Mass spectrometry is a powerful analytical technique that identifies the type and amount of chemicals present in a sample. It does so by measuring the mass-to-charge ratio of charged particles.

  • The mass spectrometer has four parts: the sample inlet, ion source, mass analyser, and detector.

  • The sample inlet introduces the sample to be analysed into the ion source. Samples can be solids, liquids, or gases. The ion source ionises the sample molecules to form positive ions.

  • Every ion source has a mechanism to produce ionising radiation and a means of accelerating the ions. There are various ways to ionise the sample molecules - Electron Impact (EI) and Chemical Ionisation (CI) are the most common.

  • The masses of the ions are then separated depending on their mass-to-charge ratio (m/z) in the mass analyser. A mass spectrometer operates by manipulating ions in an electric and/or magnetic fields.

  • The mass analyzer separates the generated ions based on their weight, charge, and shape. The separation can be done by a variety of techniques, the most popular ones being quadrupole mass analyzer, time-of-flight (TOF), ion traps, and magnetic sector.

  • The separated ions are then detected and the abundance of each m/z ratio is measured. The detector converts the separated ions into an electrical signal that can be read and interpreted by a computer.

  • Interpretation of mass spectra involves identifying the molecular ion peak (parent peak), base peak, and isotopic peak.

  • The molecular ion peak, which often can be the highest mass peak in the spectrum, correlates to the mass of the original molecule.

  • The base peak is the most abundantly produced ion in the spectrum. It is displayed as the highest peak in the spectrum and often corresponds to the most stable ion.

  • It is possible to detect isotopic peaks in the mass spectrum, which come from naturally occurring stable isotopes of elements other than Carbon-12.

  • Fragmentation patterns in the mass spectrum can give valuable clues about the structural features of the molecule.

  • Due to its high precision, mass spectrometry is an indispensable analytical technique used extensively in research labs, hospitals, and industries, especially in pharmaceuticals and environmental analysis.