1. A method for detecting an analyte, wherein the analyte is labelled with one or more labels relatable to the analyte which are suitable for optical detection, which method comprises: (a) applying an oscillating voltage having a first frequency across the labelled analyte and simultaneously performing an optical detection method on the labelled analyte to obtain data from the one or more labels; (b) applying an oscillating voltage having a second frequency across the labelled analyte and simultaneously performing an optical detection method on the labelled analyte to obtain data from the one or more labels; (c) measuring the frequency of light emission during electrochemical perturbation in steps (a) and (b) and determining the identity and/or quantity of the analyte from the data obtained, wherein the frequency of the oscillating voltage is moved through a range of frequencies from the first frequency to the second frequency and optical detection is performed simultaneously with the changing voltage to obtain data from the one or more labels over the range of frequencies.