A method for determining the concentration of an analyte is provided. The method comprises: applying an alternating voltage to a first electrode and a second electrode of a sensor in the presence of the analyte; measuring a first capacitance of the sensor in presence of the analyte; irradiating the analyte for a predetermined time period at a discrete frequency within a predetermined frequency range; measuring a second capacitance of the sensor at an end of the predetermined time period; determining a difference between the first and second capacitances; and determining the concentration of the analyte based on the difference. Also, the method includes determining a composition of an analyte. The discrete frequency is associated with the difference to determine a frequency response. The frequency response is used to determine the composition of the analyte.
