Mass spectrometry is used to measure the ratio of what two properties of molecules?

Mass spectrometry is an analytical technique that is specifically designed to measure the mass-to-charge ratio of ions. This means that the technique provides valuable information about both the mass of the ion and its charge, which is crucial for characterizing different molecules.

When a sample is introduced into a mass spectrometer, it undergoes ionization, resulting in charged particles. The mass-to-charge ratio (often expressed as m/z) allows for the identification of molecules based on their mass and the number of charges they carry. Since ions can have varying degrees of charge based on the degree to which they are ionized, measuring this ratio helps in accurately determining the molecular weight and structure of the compounds present in the sample.

This precision is what makes mass spectrometry an essential tool in fields such as proteomics, metabolomics, and drug testing, where identifying and quantifying specific molecules within complex mixtures is necessary. The other properties mentioned in the options do not relate directly to how mass spectrometry is utilized, making this choice the correct one.