The distribution of intensity, 10log(I/I
), and CV's of triplicate measured peak intensities of peptide masses in the peptide profile matrices. The value 10log(I/Imax) is 0 for the peptide mass with the highest intensity I = Imax in the peptide profile matrix. The heights of the bars in the histogram represent the number of lower intensity masses with 10log(I/Imax) < 0 of each software package, A) Peptrix, B) Sieve™, C) msInspect, and D) Progenesis™, respectively. The vertical red lines mark the relative intensities, 10log(I/Imax), of 3 peptide masses MH+, 2109.02 and 1502.76 Da of Ig kappa chain C region (Table 4), and a mass MH+ 1654.74 Da of Ig lambda-1 chain C regions. The intensity distributions of the four software packages align on the logarithm of relative intensities of the 3 peptide masses, approximately at -0.5, -1.9, and -2.2. The maximum in the distribution for each software package represents the number of features just above the signal to noise cut-off. The CV's slightly increase with lower intensity of the peptide peak intensities and more strongly at the signal to noise threshold of peak detection, 10log(I/Imax) < -4.