A method of assessing mass spectral peaks obtained by a mass spectrometer comprising: providing experimentally obtained mass spectral data; selecting a chemical compound thought to have been analysed so as to provide said experimentally observed data, and modelling the spectral data predicted to be detected if the compound was to be mass analysed, wherein said step of modelling comprises: generating a first set of spectral data including plural mass peaks that are predicted to be detected for the selected compound, wherein said step of generating the first set of spectral data comprises predicting the mass to charge ratios of said plural mass peaks that are predicted to be detected for the selected compound, and applying a peak shape to each of the plural mass peaks, wherein the peak shape of a peak at low mass to charge ratio is determined from the convolved function of a Gaussian having a small width and a quadratic having a larger width, and wherein the peak shape of a peak at higher mass to charge ratio is determined from the convolved function of a Gaussian having a width and either a quadratic having a smaller width or a delta function; generating a second set of spectral data by duplicating the first set of spectral data and shifting the duplicated plural mass peaks in mass to charge ratio relative to the corresponding plural mass peaks in the first set of spectral data; and summing the amplitudes of the first and second sets of spectral data to produce a model data set having plural mass peaks; said method further comprising comparing the model data set to the experimentally obtained data; determining that the model data set matches the experimentally obtained mass spectral data; and identifying a defect in the experimentally obtained data from the first and/or second sets of data. providing experimentally obtained mass spectral data; selecting a chemical compound thought to have been analysed so as to provide said experimentally observed data, and modelling the spectral data predicted to be detected if the compound was to be mass analysed, wherein said step of modelling comprises: generating a first set of spectral data including plural mass peaks that are predicted to be detected for the selected compound, wherein said step of generating the first set of spectral data comprises predicting the mass to charge ratios of said plural mass peaks that are predicted to be detected for the selected compound, and applying a peak shape to each of the plural mass peaks, wherein the peak shape of a peak at low mass to charge ratio is determined from the convolved function of a Gaussian having a small width and a quadratic having a larger width, and wherein the peak shape of a peak at higher mass to charge ratio is determined from the convolved function of a Gaussian having a width and either a quadratic having a smaller width or a delta function; generating a second set of spectral data by duplicating the first set of spectral data and shifting the duplicated plural mass peaks in mass to charge ratio relative to the corresponding plural mass peaks in the first set of spectral data; and summing the amplitudes of the first and second sets of spectral data to produce a model data set having plural mass peaks; generating a first set of spectral data including plural mass peaks that are predicted to be detected for the selected compound, wherein said step of generating the first set of spectral data comprises predicting the mass to charge ratios of said plural mass peaks that are predicted to be detected for the selected compound, and applying a peak shape to each of the plural mass peaks, wherein the peak shape of a peak at low mass to charge ratio is determined from the convolved function of a Gaussian having a small width and a quadratic having a larger width, and wherein the peak shape of a peak at higher mass to charge ratio is determined from the convolved function of a Gaussian having a width and either a quadratic having a smaller width or a delta function; generating a second set of spectral data by duplicating the first set of spectral data and shifting the duplicated plural mass peaks in mass to charge ratio relative to the corresponding plural mass peaks in the first set of spectral data; and summing the amplitudes of the first and second sets of spectral data to produce a model data set having plural mass peaks; said method further comprising comparing the model data set to the experimentally obtained data; determining that the model data set matches the experimentally obtained mass spectral data; and identifying a defect in the experimentally obtained data from the first and/or second sets of data.