A system, components thereof, and methods are described for time-of-flight mass spectrometry. A microwave or high-frequency RF energy source is used to ionize a reagent vapor to form reagent ions. The reagent ions enter a chamber and interact with a fluid sample to form product ions. The reagent ions and product ions are directed to a time-of-flight mass spectrometer module for detection and determination of a mass value for the ions. The time-of-flight mass spectrometer module can include an optical system and an ion beam adjuster for focusing, interrupting, or altering a flow of reagent and product ions according to a specified pattern. The time-of-flight mass spectrometer module can include signal processing techniques to collect and analyze an acquired signal, for example, using statistical signal processing, such as maximum likelihood signal processing.