A multiplex sensor and a method of use that provides enhanced selectivity and sensitivity. In this method, one or more parameters of the sample are measured by means of multiple spectroscopic techniques, and the interferences from physiological and spectral variables are reduced or eliminated. In one embodiment of the present invention comprises a multiplex sensor and a method of use that provides enhanced selectivity and sensitivity. One or more parameters of the sample are measured by means of at least two different spectroscopic techniques, wherein the at least two different spectroscopic techniques are selected from the group consisting of: (a) infrared absorbance (b) scattering (c) emission (d) polarization, and (e) photoacoustics.