Matrix-assisted ionization

Matrix-assisted inlet ionization In Matrix-assisted inlet ionization (MAII), a matrix which can be a solvent is used at ambient temperature with the analyte of interest as a mixture. The matrix/analyte mixture is inserted into the heated inlet tube through tapping the mixture at the opening end of the tube. For the highly charged ions of the analyte to be produced from ionization, desolvation of the matrix molecules needs to occur. Matrices that can be used include: As all inlet ionization techniques, highly multiply charged ions are produced. A nitrogen laser is used to ablate the solid matrix/analyte into the heated inlet tube, the observed ions are generated at the surface of the matrix/analyte and so the laser is not directly involved in the ionization as was originally thought. Solvent assisted inlet ionization Solvent assisted inlet ionization (SAII) is similar to matrix-assisted inlet ionization however the matrix is a solvent such as water, acetonitrile and methanol. The temperature can vary in the inlet tube from 50 °C to 450 °C, with the lower temperature being used if the results obtained from a higher temperature are of good resolution. Solvent assisted inlet ionization can be coupled not only to liquid chromatography (LC) but also to nano LC. == Advantages of inlet ionization ==

Ionization at atmospheric pressure often leads to a loss of ions during the transfer of the ions from the ambient pressure region to the vacuum of the mass analyzer. Ions are lost due to dispersion of analyte spray and 'rim loss' causing fewer ions to reach the vacuum for m/z separation to occur. Initial ionization occurs in the sub-atmospheric pressure region of the heated inlet tube which is directly attached to the vacuum of the mass analyzer and so ion loss is reduced as transfer of the ions does not occur. In LSII the use of the laser increases the image quality of the results by producing better spatial resolution. == References ==