A Method for Extracting Mass Information from Low Resolution Mass-to-Charge Ratio Spectra of Multiply Charged Species

A method for extracting mass information from low resolution mass-to-charge ratio spectra of multiply charged species to identify a mass of a polyatomic parent molecule within the multiply charged species, the method comprising the steps of:

• receiving from a mass spectrometer a data set indicative of a population of multiply charged ions, the number of charges on each ion defining the charge state of that ion, wherein a sub-population of ions within said population of ions comprises ions of said population of ions having a same charge state;
• using the data set indicative of a population of multiply charged ions to produce an input mass-to-charge ratio spectrum, the sub-populations of each charge state being represented by intensities in the mass-to-charge ratio spectrum;
• processing the input mass-to-charge ratio spectrum to provide a signal enhanced mass-to-charge ratio spectrum, the signal enhanced mass-to-charge ratio spectrum being generated from a logarithm of the quotient of said mass-to-charge ratio spectrum and a smoothed representation of said mass-to-charge ratio spectrum;
• identifying a range of defined charged mass values of a defined charged mass spectrum within which to search for a mass of the polyatomic parent molecule;
• generating for each mass within said range of defined charged mass values a summation equal to the addition of values in the signal enhanced mass-to-charge ratio spectrum that correspond to said mass at sequential charge states up to a maximum charge state using the function:
• F
• 
• (
• M
• )
• =
• ∑
• n
• =
• 1
• n
• =
• n
• max
• 
• 
• X
• 
• (
• M
• -
• zm
• a
• n
• +
• m
• a
• )
• Where M is any defined mass within said range of defined charged mass values;
• ma is the mass of the charge carrying adduct;
• z is the order of the defined charged mass spectrum and X is a distribution function of the signal enhanced mass-to-charge ratio spectrum;
• and
• using said summation values to determine the mass of a polyatomic parent molecule.