Method and system of detecting a target analyte

The invention relates to a method and system of detecting the presence of one or more specific target analytes in a sample. The method comprises the steps of exposing a SERS-active surface to the sample so as to capture analytes from the sample by adherence to the SERS-active surface; acquiring an ensemble X of Raman/SERS-spectra measured at different locations on the SERS-active surface; for each target analyte, determining a target spectrum representative of that target analyte; modelling the ensemble X of measured Raman/SERS-spectra using a factorization-model, wherein the factorization-model includes a loadings matrix A times a spectral component matrix S, wherein matrix elements of A and S are all real and non-negative; jointly estimating parameters in the factorization-model, the estimated parameters including at least A and S; for each target analyte, selecting amongst the spectral components of S a target component corresponding to the target spectrum of that target analyte; and determining presence of the one or more target analytes at least on the basis of the estimated loadings for the selected target components. During estimation at least one of the one or more target components is populated according to a p re-determined function.