We show development of a laser desorption/ionization (LDI) method with ultrahigh sensitivity by adding gold nanoparticles with a diameter of several tens of nanometers into a sample solution. In this paper, we succeeded in detection of an ultratrace amount of sample molecules, which is less than several hundred zeptomoles. This result suggest that the charge interaction based on surface plasmon (SP) excitation is very effective for ultrahigh sensitivity in LDI method.

We researched contribution of a charge transfer (CT) effect to desorption/ionization mechanism in our ultra-high sensitive laser desorption/ionization mass spectrometry based on surface plasmon (SP) excitation (SPLDI-MS). A quantity of CT electrons between a metal surface and sample molecules estimated from Raman measurement is correlated to a mass signal intensity of sample molecule in our SPLDI-MS method. A sample system with a larger quantity of CT electrons gave a higher mass signal intensity. Efficient use of the CT effect would lead to development of a higher sensitive SPLDI-MS and this development would contribute to advancement of various fields.