Which part of the mass spectrometer involves the ionization and selective monitoring of sample components?

The ion source is the critical part of the mass spectrometer where ionization occurs, transforming sample molecules into charged particles (ions) that can be analyzed. This process is essential, as only ions can be accelerated and directed through the remainder of the mass spectrometer.

In this component, the sample is introduced, typically in a gaseous state, and subjected to energy via various methods such as electron impact or chemical ionization. This energy causes the molecules to become ionized, allowing each component of the sample to be selectively monitored as they are transformed into ions of different mass-to-charge ratios.

The functioning of the ion source directly impacts the quality and type of ions produced, which is foundational for the subsequent analysis performed by other components of the mass spectrometer, such as the mass analyzer and detector. Hence, the ion source is integral to identifying and quantifying the components of the sample being studied.