Resolution and Mass Accuracy on the Perseptive Biosystems Voyager DE-PRO
Molecular
mass terms
Average mass-mass
calculated by summing
the average atomic mass of the constituent elements
H = 1.00794
Monoisotopic mass-mass calculated by summing the most abundant isotope's atomic mass of the constituent elements-usually used with low (< 2000 Da) molecular weight compounds
H = 1.007825
Resolution
Resolution is expressed as m/Δm
and can be defined in two different ways:
-
10% valley-a pair of adjacent ion peaks at m1 and m2 are resolved so that a valley of 10% is observed between them, relative to the least abundant ion of the pair, Δm is the main difference between m1 and m2
-
full-width, half-maximum (FWHM)-the width of an ion at mass m, at 50% abundance is used to define Δm
Resolutions determined using FWHM are about twice the resolutions determined using the 10% valley method. Figure 1 shows the importance of resolution when analyzing small peptides.
Figure 1: Importance
of resolution when analyzing small peptides.
Resolution (FWHM) of the Perseptive Biosystems Voyager DE-PRO
|
Linear Mode |
|||
|
Resolution |
Analyte |
Concentration |
Average MW [M+H]+ |
|
≥50 |
IgG |
1 pmol/µL |
~150,000 |
|
≥80 |
BSA |
5 pmol/µL |
64431 |
|
≥1,000 |
Myoblobin |
5 pmol/µL |
16952.56 |
|
≥2,000 |
Angiotensin I |
1 pmol/µL |
1297.51 |
|
Reflector Mode |
|||
|
Resolution |
Analyte |
Concentration |
Average MW [M+H]+ |
|
≥10,000 |
bovine insulin |
5 pmol/µL |
5734.59 |
|
≥1,200 |
E. coli Thioredoxin |
5 pmol/µL |
11674.48 |
|
≥7,000 |
Angiotensin |
2.0 pmol/µL |
1297.51 |
|
≥7,000 |
ACTH clips |
|
|
|
|
ACTH 1-17 |
2.0 pmol/µL |
2094.46 |
|
|
ACTH 18-39 |
1.5 pmol/µL |
2466.72 |
|
|
ACTH 7-38 |
3.0 pmol/µL |
3660.19 |
Mass
accuracy
Mass accuracy can be
expressed as
either a percentage of the measured mass or in parts-per-million
(ppm). For example, mass = 2,000 Da ±
0.01% or mass = 2,000 Da ±
100 ppm. Since this is expressed as a percentage, as the
mass
of the analyte increases, the absolute mass error will increase as
well. This is shown in the table below:
|
Percent |
ppm |
m/z |
Mass Error |
|
0.01% |
100 |
1,000 Da |
0.1 Da |
|
0.01% |
100 |
5,000 Da |
0.5 Da |
|
0.01% |
100 |
50,000 Da |
5 Da |
Mass Accuracy on the Perseptive Biosystems Voyager DE-PRO
|
Linear Mode |
||
|
Calibration type |
Percent |
ppm |
|
External calibration |
0.05% |
500 |
|
Internal calibration |
0.02% |
200 |
|
Reflector Mode |
||
|
Calibration type |
Percent |
ppm |
|
External calibration |
0.01% |
100 |
|
Internal calibration |
0.002% |
20 |
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