Provided here are methods, apparatuses, and systems directed to the determination of geochemical properties of liquid hydrocarbons based on the dielectric properties of components of the liquid hydrocarbons using microwaves. Also disclosed is a method for characterizing a geochemical property of a liquid hydrocarbon by measuring the dielectric responses from a portion of the liquid hydrocarbon at different predetermined temperatures in two or more microwave resonant cavities to electromagnetic waves at select microwave frequencies, and determining a geochemical property of the liquid hydrocarbon in response to measurements of the dielectric responses.