Embodiments herein relate to systems and devices for measuring analyte presence on graphene varactors, which can be used for analyte sensing in physiological gas samples. In an embodiment, a system for measuring analyte presence on a graphene varactor is included having a capacitance to digital converter (CDC) and a graphene varactor. The CDC can be in electrical communication with the graphene varactor and can be configured to measure the capacitance of the graphene varactor in response to an excitation signal over a plurality of DC bias voltages. Other embodiments are also included herein.