A method for quantitative determination of an analyte in a test item using a NMR spectrometer, the method comprises the steps: providing a sample solution by dissolving a defined amount of the test item in a defined amount of a deuterated solvent, calibrating the NMR spectrometer by determining a calibration factor related to a first and a second NMR-active nuclide, wherein the first NMR-active nuclide is a constituent of the deuterated solvent and the second NMR-active nuclide is a constituent of the analyte; generating a first spectrum by performing a first NMR experiment on the sample solution to determine the resonance frequencies of the first NMR-active nuclide; generating a second spectrum by performing a second NMR experiment on the sample solution to determine the resonance frequencies of the second NMR-active nuclide, and calculating the mass of analyte in the sample solution taking into account the signals in the first and second spectra and taking into account the calibration factor, wherein the first NMR-active nuclide and the second NMR-active nuclide are different from each other, the calibration factor is determined by determining the resonant frequencies of the first NMR-active nuclide and the second NMR-active nuclide in a calibration solution containing known amounts of the first NMR-active nuclide and the second NMR-active nuclide, generating two calibration spectra and comparing the signals of the first NMR-active nuclide and the second NMR-active nuclide in the calibration spectra, and the first and the second NMR experiments and the determination of the calibration factor are carried out using the same NMR spectrometer. providing a sample solution by dissolving a defined amount of the test item in a defined amount of a deuterated solvent, calibrating the NMR spectrometer by determining a calibration factor related to a first and a second NMR-active nuclide, wherein the first NMR-active nuclide is a constituent of the deuterated solvent and the second NMR-active nuclide is a constituent of the analyte; generating a first spectrum by performing a first NMR experiment on the sample solution to determine the resonance frequencies of the first NMR-active nuclide; generating a second spectrum by performing a second NMR experiment on the sample solution to determine the resonance frequencies of the second NMR-active nuclide, and calculating the mass of analyte in the sample solution taking into account the signals in the first and second spectra and taking into account the calibration factor, wherein the first NMR-active nuclide and the second NMR-active nuclide are different from each other, the calibration factor is determined by determining the resonant frequencies of the first NMR-active nuclide and the second NMR-active nuclide in a calibration solution containing known amounts of the first NMR-active nuclide and the second NMR-active nuclide, generating two calibration spectra and comparing the signals of the first NMR-active nuclide and the second NMR-active nuclide in the calibration spectra, and the first and the second NMR experiments and the determination of the calibration factor are carried out using the same NMR spectrometer. wherein the first NMR-active nuclide and the second NMR-active nuclide are different from each other, the calibration factor is determined by determining the resonant frequencies of the first NMR-active nuclide and the second NMR-active nuclide in a calibration solution containing known amounts of the first NMR-active nuclide and the second NMR-active nuclide, generating two calibration spectra and comparing the signals of the first NMR-active nuclide and the second NMR-active nuclide in the calibration spectra, and the first and the second NMR experiments and the determination of the calibration factor are carried out using the same NMR spectrometer.