An ultrasonic transmitter (95) and detector (e.g., integrated as an ultrasound transducer) utilized in a feedback control system automatically monitors and/or detects surface profile (e.g., shape) of the liquid-air interface and adjusts the flow rate of sampling liquid to ensure that experimental conditions remain consistent at the time of sample introduction during serial samplings. The feedback control can provide for automated adjustment of the surface profile of the liquid-air interface in accordance with changes in desired set point according to an experimental workflow (e.g., automated adjustment between an interface corresponding to a vortex sampling set point and an overflow cleaning set point). Improvements in desorption efficiency and quality of mass spectrometry data by degassing of the liquid solvent utilized within the sampling interfaces, and/or utilization in a feedback control system for generating data indicative of a surface profile of the liquid-air interface within the interface's sampling port may be realized.