Abstract: A method to analyze a sample includes performing sample interrogation cycles on the sample to generate replicates. Each of the sample interrogation cycles is performed by: illuminating the sample with two or more fluorescence excitation signals at different wavelengths; and detecting both a fluorescence emission spectral profile and a fluorescence lifetime profile of the sample for each of the two or more fluorescence excitation signals to generate two or more fluorescence emission spectral profiles and two or more fluorescence lifetime profiles of the sample. Each replicate includes the two or more fluorescence emission spectral profiles and the two or more fluorescence lifetime profiles generated for a corresponding one of the sample interrogation cycles. The method includes performing a comparison of the replicates to predetermined spectroscopic relationships.