this invention relates generally to methods and apparatus for desorption and ionization of analytes for the purpose of subsequent scientific analysis by such methods , for example , as mass spectrometry or biosensors . more specifically , this invention relates to the field of mass spectrometry , especially to the type of matrix - assisted laser desorption / ionization , time - of - flight mass spectrometry used to analyze macromolecules , such as proteins or biomolecules . most specifically , this invention relates to the sample probe geometry , sample probe composition , and sample probe surface chemistries that enable the selective capture and desorption of analytes , including intact macromolecules , directly from the probe surface into the gas phase without added chemical matrix .