A method of analyzing a biological sample using an analyzer and an assay, wherein the analyzer is operable for measuring a signal indicative of an intensive property of an analyte in the biological sample, wherein the intensive property is a concentration of the analyte, wherein the analyzer comprises a photometric measurement module operable for measuring the signal, and wherein the signal is at least a portion of a photometric transmission spectra, wherein the method comprises: - providing the assay, wherein the assay is operable to produce the signal, wherein the assay has a predetermined number of components wherein the predetermined number of components is two, wherein each of the predetermined number of components has a distinct relation between the intensive property and the signal, wherein each of the predetermined number of components is a distinct assay; - providing (102, 200) a set number of calibration samples with known values for the intensive property, wherein the set number is two times the predetermined number of components plus one, two, three, four or five; - measure (104, 202) a calibration signal for each of the calibration samples using the analyzer and the assay; - determining (106, 206) a calibration by fitting a calibration function to the calibration signal for each of the calibration samples and the known values for the intensive property, wherein the calibration function is equivalent to a constant plus an exponential decay term for each of the predetermined number of components, wherein the calibration function is a sum of two exponential decay terms, wherein each exponential decay term has two calibration parameters; - measuring (108, 208) the signal of the biological sample using the analyzer and the assay; and - calculating (110, 210) the intensive property using the signal and the calibration. - providing the assay, wherein the assay is operable to produce the signal, wherein the assay has a predetermined number of components wherein the predetermined number of components is two, wherein each of the predetermined number of components has a distinct relation between the intensive property and the signal, wherein each of the predetermined number of components is a distinct assay; - providing (102, 200) a set number of calibration samples with known values for the intensive property, wherein the set number is two times the predetermined number of components plus one, two, three, four or five; - measure (104, 202) a calibration signal for each of the calibration samples using the analyzer and the assay; - determining (106, 206) a calibration by fitting a calibration function to the calibration signal for each of the calibration samples and the known values for the intensive property, wherein the calibration function is equivalent to a constant plus an exponential decay term for each of the predetermined number of components, wherein the calibration function is a sum of two exponential decay terms, wherein each exponential decay term has two calibration parameters; - measuring (108, 208) the signal of the biological sample using the analyzer and the assay; and - calculating (110, 210) the intensive property using the signal and the calibration.