Patent ID: 8158930

Claim:
A method of producing a calibrated mass spectrum, comprising: a) providing a sample comprising two or more analytes; b) subjecting the sample to mass spectrometry to obtain a mass spectrum, wherein the mass spectrum comprises un-calibrated data; c) extracting the peaks from the spectrum and assigning a position and an ion charge to each peak; d) providing input parameters comprising: (i) initial estimates of calibration parameters wherein the calibration parameters relate the observed peaks in the mass spectrum to mass-to-charge ratio; and (ii) initial estimate of root-mean-squared error in the calibrated mass values; e) providing a list of masses of analytes from a database to provide candidate analytes present in the sample, wherein a database comprises a list of elemental compositions and corresponding mass values; f) converting each peak position determined in step (c) to an estimated mass-to-charge ratio using the input parameters; g) calculating an estimated mass of the neutral analyte molecule from the mass-to-charge ratio estimate in step (f) and the ion charge determined in step (c); h) assigning probabilities to one or more entries in the database as the identity of the analyte based on the estimate of the mass from step (g) and the estimate of root-mean-squared error; i) updating the estimated values of the calibration parameters based on the assigned probabilities in step (h); j) updating the estimated root-mean-squared error using the updated calibration parameters from step (i); and k) repeating steps f) through i) until convergence is reached, whereby a calibrated mass spectrum is produced and candidate identities are assigned to each peak in the spectrum.