A method for laser induced breakdown spectroscopy (LIBS) calibration or LIBS assay comprises providing a plurality of reference samples, each having a respective, known concentration of an analyte, assaying each reference sample to obtain a respective LIBS spectrum, and for each reference LIBS spectrum, measuring an intensity of at least one spectral analyte line that varies with concentration of the analyte, and measuring a peak amplitude of at least one saturating line of a reference element. The ratio and known concentrations define a calibration curve for the analyte.