There are multiple methods for mass spectrometry and means of ionization. However most of them are not suitable for samples from the organometallic / elementorganic field since inert application methods and soft ionization is usually necessary. In these cases the LIFDI-MS (Liquid Injection Field Desorption Ionization Mass Spectrometry) method has proven its strength. Samples are applied with a capillary through a septum from a sealed vial while the ionization method itself is also amongst the softest there is. For more information on LIFDI-MS I recommend reading this website (external link).