A newly developed noncontact high-resolution real-time microwave sensor was used to determine the breakthrough time and adsorption capacity of adsorbents/adsorbates with different dielectric properties. The sensor is a microwave microstrip planar resonator with an enhanced quality factor using a regenerative feedback loop operating at 1.4 GHz and an adjustable quality factor of 200-200000. Beaded activated carbon (BAC, microwave-absorbing) and a polymeric adsorbent (V503, microwave transparent) were completely loaded with 1,2,4-trimethylbenzene (nonpolar) or 2-butoxyethanol (polar). During adsorption, variations in the dielectric properties of the adsorbents were monitored using two microwave parameters; quality factor and resonant frequency. Those parameters were related to adsorption breakthrough time and capacity. Adsorption tests were completed at select relative pressures (0.03, 0.1, 0.2, 0.4, and 0.6) of adsorbates in the influent stream. For all experiments, the difference between the breakthrough time (t5%) and the settling time of the quality factor variation (time that the quality factor was 0.95 of its final value) was <5%. Additionally, a linear relationship between the final value of the resonant frequency shift and adsorption capacity was observed. The proposed noncontact sensor can be used to determine the breakthrough time and adsorption capacity.