Abstract: This application relates to a process for controllably placing two or more microspots on a target substrate in close proximity to one another. The microspots may then be simultaneously irradiated and the resulting ions detected by mass spectrometry, such as time of flight mass spectrometry. In one embodiment the size and spacing of the microspots on the substrate may be controlled by using an electrodynamic balance during the deposition step. The deposition procedure ensures that at least some of the microspots are spaced-apart on the substrate a distance less than the focused output of a single laser. Simultaneous irradiation of the adjacent microspots may cause desorption plumes of the microspots to interact in a gas phase, such as by ion-molecule reactions. The microspots may be configured to improve the ionization yield of the sample material in the gas phase and/or to increase the frequency of ion-molecule collisions in the gas phase.

Abstract: This application is concerned with the controlled nucleation of solutes (i.e. dissolved solids) from solution. It has been found that the energy barrier for dissolved solids to nucleate is affected by the surface charge density of the reaction vessel (and hence the mass-to-charge ratio of vessel). The reaction vessel may, for example, comprise a levitated droplet of the solution having an “excess net charge”. That is, ions present in the vessel of a single polarity are in excess of the counterions of opposite polarity. An increase in the surface charge density of the vessel (and hence a reduction in the mass-to-charge ratio of the vessel) causes the barrier for nucleation to decrease. These findings can be exploited using instruments commonly used in wall-less sample preparation to elicit selective control over the induction of nucleation and subsequent crystallization of target solutes of interest in the condensed phase.