Laser-induced desorption LDMS

This technique was introduced by Posthumus et al. [96] in 1978. The ions can be produced in an El source (LDEIMS). The laser beam is obtained with either a pulsed COj or ruby neodynium type YAG laser. Here again, the technique is useful for labile 

More recently. Cotter and co-worker [98] used a Cl source to study with a greater sensitivity desorbed neutrals from glucuronic conjugated steroids and bile acids. Hunt et al. [99] utilized the same ionization method (CI/Ar) and showed the presence of 50 ng of strychnine. Studying trisaccharides they observed cationized ions, such as [M + Na][M + K] and [M -l- Cs] in their respective mass spectra. 

Peptides were also investigated thus, the molecular peak at m/z 555 was obtained corresponding to Tyr-Gly-Gly-Phe-Leu peptide and fragment ions corresponding to peptide sequence. 

More recently, Schueler and Kreuger [100] compared these two latter desorption methods, PDMS (or FFID) and LDMS (or LID), in a study of nucleoside compounds and their corresponding bases (Fig. 13). 

Common fragmentations appeared in each of the spectra, especially in those of adenosine, recorded in negative ionization mode. 

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Fast-atom bombardment mass spectrometry (FAB-MS) has been applied to the identification of diterpenoid compounds and their oxidation products. Similarly, laser-induced desorption mass spectrometric (LDMS) techniques have been applied to the identification of natural and synthetic organic pigments in microscopic paint samples prepared as cross sections [60]. 

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