Atmospheric pressure mass spectrometric imaging of bio-tissue specimen using electrospray-assisted CW laser desorption and ionization source.

When a tissue slice pretreated with gold nanoparticles is irradiated with a focused 532-nm continuous wave laser, desorption is observed to be uniform and stable, and its shape is sharp and steep. However, since the desorbed molecules are still electrically neutral particles in atmospheric pressure (AP), additional procedure of ionizing them is necessary for AP mass spectrometry (AP-MS) analysis. Therefore, the authors have combined an electrospray device with a simple chamber connected to the airflow-assisted particle transport equipment mounted at the mass spectrometer inlet. Subsequent ionization processes using an electrospray device enable the detection of several types of diacylglycerol molecules above 500 Da, which cannot be detected with the use of AP plasma jets. The authors also developed a remote AP-MS using a long and flexible sampling probe and a fiber laser with a slight modification of the proposed AP desorption and ionization method.