Mass_spectrometry

 Maldi TOF Mass Spectrometry

Mass spectrometry is an analytical tool used for measuring the molecular mass of a sample. Mass spectrometers can be divided into three fundamental parts, namely the ionisation source, the analyser, and the detector. The sample has to be introduced into the ionisation source of the instrument. Once inside the ionisation source, the sample molecules are ionised. These ions are extracted into the analyser region of the mass spectrometer where they are separated according to their mass (m) -to-charge (z) ratios (m/z) . The separated ions are detected and this signal sent to a data system where the m/z ratios are stored together with their relative abundance for presentation in the format of a m/z spectrum .The analyser and detector of the mass spectrometer, and the ionisation source are maintained under high vacuum to give the ions a reasonable chance of travelling from one end of the instrument to the other without any hindrance from air molecules.

MALDI is based on the bombardment of sample molecules with a laser light to bring about sample ionisation. The sample is pre-mixed with a highly absorbing matrix compound but (for LDI mode) for the most consistent and reliable results, and a low concentration of sample to matrix works best. The matrix transforms the laser energy into excitation energy for the sample, which leads to sputtering of analyte and matrix ions from the surface of the mixture. In this way energy transfer is efficient and also the analyte molecules are spared excessive direct energy that may otherwise cause decomposition. Commercially available MALDI mass spectrometers now have a pulsed nitrogen laser of wavelength 337 nm.

Fullerene extract