Table 2.
A fragment of mass and intensity peaks lists of 2 samples, illustrating the "missing data" problem.
| A) | ||||
| Sample 1 | Sample 2 | |||
| Mass (Da) | Intensity (A.U.) | Mass (Da) | Intensity (A.U.) | |
| ? | ← | 1193.6166 | 756021 | |
| ? | ← | 1194.5728 | 191048 | |
| 1194.6477 | 175777 | 1194.6477 | 271465 | |
| 1197.1376 | 126487 | → | ? | |
| ? | ← | 1197.6611 | 124472 | |
| ? | ← | 1198.5193 | 162275 | |
| 1198.7047 | 3154774 | 1198.7047 | 2435350 | |
| B) | ||||
| Sample 1 | Sample 2 | |||
| Mass (Da) | Intensity (A.U.) | Mass (Da) | Intensity (A.U.) | |
| 0 | ← | 1193.6166 | 756021 | |
| 114322 | ← | 1194.5728 | 191048 | |
| 1194.6477 | 175777 | 1194.6477 | 271465 | |
| 1197.1376 | 126487 | → | 80604 | |
| 0 | ← | 1197.6611 | 124472 | |
| 0 | ← | 1198.5193 | 162275 | |
| 1198.7047 | 3154774 | 1198.7047 | 2435350 | |
A) Missing data problem. It appears that the signal intensity from of a peptide mass of 1193.6166 Da in sample 2 is not matched with an intensity of the peptide mass from another sample 1 and vice versa the intensity of peptide mass of 1197.1376 Da of sample 2 is not observed in sample 1.
B) More reliable comparison including background noise signal by recording all the peaks with intensities between the baseline and the S/N threshold in a "noise peaks" file.
A.U. = arbitrary units