An apparatus or method determines a salinity or metal content a liquid sample by scanning the liquid sample using a PXRF spectrometer, receiving a PXRF spectra from the PXRF spectrometer, baseline correcting and smoothing the received PXRF spectra, extracting a Kα emission line of one or more elements from the baseline corrected and smoothed PXRF spectra using only one beam from the PXRF spectrometer, determining the salinity or the metal content of the liquid sample using the one or more processors and a predictive model that relates the Kα emission line of the one or more elements to the salinity or the metal content of the liquid sample, and providing the salinity or the metal content of the liquid sample to the one or more input/output interfaces.