Fragmenting ions in mass spectrometry
View Patent ↗Systems, methods, and computer program products useful in controlling the fragmentation of ions. Control of fragmentation is achieved by varying the collision energy imparted to precursor ions.
1. A method of controlling the fragmentation of ions during mass spectral analysis, comprising:
(i) at a starting collision energy provided within a mass spectrometer, fragmenting at least one of a plurality of precursor ions generated from a sample to produce a plurality of daughter ion fragments;
(ii) determining an ion current associated with unfragmented precursor ions in the mass spectrometer;
(iii) determining an ion current associated with the daughter ion fragments in the mass spectrometer;
(iv) determining the ratio of the current associated with the unfragmented precursor ions to the current associated with the daughter ion fragments; and
(v) adjusting the collision energy provided in the mass spectrometer at (i) to move the ratio toward a predetermined range or value.
2. The method of claim 1 , further comprising repeating (i)-(v), as necessary, to bring the ratio into the predetermined range.
3. The method according to claim 1 , wherein the collision energy is adjusted by an amount determined using the relation:
Δ CE=m *ln (ion current ratio)+ B,
where ΔCE is the change by which the collision energy is adjusted; and m and B are constants derived through at least one of theoretical analysis and experimentation.
4. The method according to claim 3 , wherein the collision energy is adjusted by an amount determined using the relation:
Δ CE= 4.5*ln (ion current ratio)+13.5 (eV).
5. A system useful for controlling the fragmentation of ions during mass spectral analysis, the system comprising a controller adapted to:
(i) at a starting collision energy provided within a mass spectrometer, fragment at least one of a plurality of precursor ions generated from a sample to produce a plurality of daughter ion fragments;
(ii) determine an ion current associated with unfragmented precursor ions in the mass spectrometer;
(iii) determine an ion current associated with the daughter ion fragments in the mass spectrometer;
(iv) determine the ratio of the current associated with the unfragmented precursor ions to the current associated with the daughter ion fragments; and
(v) adjust the collision energy provided in the mass spectrometer at (i) to move the ratio toward a predetermined range or value.
6. The system of claim 5 , wherein the controller is adapted to repeat (i)-(v), as necessary, to bring the ratio into the predetermined range.
7. The system of claim 5 , wherein the collision energy is adjusted by an amount determined using the relation:
Δ CE=m *ln (ion current ratio)+ B,
where ΔCE is the change by which the collision energy is adjusted; and m and B are constants derived through at least one of theoretical analysis and experimentation.
8. The system of claim 7 , wherein the collision energy is adjusted by an amount determined using the relation:
Δ CE= 4.5*ln (ion current ratio)+13.5 (eV).
9. A computer usable medium having computer readable code embodied therein for causing a mass spectrometer to:
(i) at a starting collision energy provided within a mass spectrometer, fragment at least one of a plurality of precursor ions generated from a sample to produce a plurality of daughter ion fragments;
(ii) determine an ion current associated with unfragmented precursor ions in the mass spectrometer;
(iii) determine an ion current associated with the daughter ion fragments in the mass spectrometer;
(iv) determine the ratio of the current associated with the unfragmented precursor ions to the current associated with the daughter ion fragments; and
(v) adjust the collision energy provided in the mass spectrometer at (i) to move the ratio toward a predetermined range or value.
10. The medium of claim 9 , comprising code adapted for causing the mass spectrometer to repeat (i)-(v), as necessary, to bring the ratio into the predetermined range.
11. The medium of claim 9 , wherein the collision energy is adjusted by an amount determined using the relation:
Δ CE=m *ln (ion current ratio)+ B,
where ΔCE is the change by which the collision energy is adjusted; and m and B are constants derived through at least one of theoretical analysis and experimentation.
12. The medium of claim 11 , wherein the collision energy is adjusted by an amount determined using the relation:
Δ CE= 4.5*ln (ion current ratio)+13.5 (eV).