Laser mass analysis in biology

Since the development of laser microprobe mass analysis, a large number of investigations have shown the versatility of the technique for biological and medical applications. The main advantages are high sensitivity and a spatial resolution in the μm‐range. Several approaches were used to test the possibility for a quantitative analysis, using internal standards. So far absolute quantification is in general not possible. Nearly all laser microanalysis investigations concerned the spatial distributions of elements (mainly metal ions) in a biological matrix. In a few cases the local organic composition was mapped by “fingerprinting”. Only in a small number of investigations could molecular constituents in the sampled microarea be observed and identified directly out of their native surroundings. Laser desorption/ionization (LDI) as an ionization method for mass spectrometric analysis of bioorganic substances on the other hand has proven to be a useful technique of its own. For ultraviolet‐LDI pioneering work has been done towards understanding of the processes of energy deposition and ion formation. As a result of this a matrix technique was developed, which now is able to generate intact molecular ions of proteins up to the 100000 dalton mass range and above.