Tuning multipole RF amplitude for ions not present in calibrant
A mass spectrometry apparatus includes an ion source configured to generate ions; an ion guide configured to guide ions from the ion source towards a detector; the ion detector configured to detect ions; and a mass spectrometry controller. The mass spectrometry controller is configured to generate a tune curve for the ion guide; determine an observed low mass cutoff for the ion guide from the tune curve; calculate an effective r0 for the ion guide based on the observed low mass cutoff; determine an RF voltage based on the effective r0 and the RF frequency; apply the RF voltage to the ion guide; and perform a mass analysis of ions in a sample.
1. A mass spectrometry apparatus comprising:
an ion source configured to generate ions;
an ion guide configured to guide ions from the ion source towards a detector;
the ion detector configured to detect ions; and
a mass spectrometry controller configured to:
generate a tune curve for the ion guide;
determine an observed low mass cutoff for the ion guide from the tune curve;
calculate an effective r0 for the ion guide based on the observed low mass cutoff;
determine an RF voltage based on the effective r0 and the RF frequency;
apply the RF voltage to the ion guide; and
perform a mass analysis of ions in a sample.
2. The mass spectrometry system of claim 1 wherein the ion guide is a quadrupole, a square quadrupole, a hexapole, an octopole, a stacked ring ion guide, an ion funnel, an ion carpet, or any combination thereof.
3. The mass spectrometry system of claim 1 wherein the processor is configured to calculate the effective r0 based on the observed low mass cutoff, a nominal r0, and an expected low mass cutoff.
4. The mass spectrometry system of claim 3 wherein the processor is configured to calculate the effective r0 according to
r
0
effective
=
K
observed
*
r
0
nominal
2
/
K
expected
where K expected is the expected value for a parameter and K observed is the observed value for the parameter, the parameter selected from q, q*(m/z), q*(m/z)*ω 2 , q*(m/z)*f 2 , V, V/ω 2 , V/f 2 , or a combination thereof.
5. The mass spectrometry system of claim 3 wherein the processor is configured to calculate the effective r0 according to
r
0
effective
=
cutoff
observed
*
r
0
nominal
2
/
cutoff
expected
.
6. The mass spectrometry system of claim 1 wherein the observed low mass cutoff is an average across at least two calibrant ion species.
7. The mass spectrometry system of claim 1 wherein the RF voltage is determined based on the effective r0, the frequency of the RF voltage, and a tune table.
8. The mass spectrometry system of claim 7 wherein the tune table includes optimum q values for mass-to-charge ratios.
9. A method of analyzing ion fragments, comprising:
generating a tune curve for an ion guide;
determining an observed low mass cutoff for the ion guide from the tune curve;
calculating an effective r0 for the ion guide based on the observed low mass cutoff;
determining an RF voltage based on the effective r0 and the RF frequency;
applying the RF voltage to the ion guide; and
performing a mass analysis of ions in a sample.
10. The method of claim 9 wherein the ion guide is a quadrupole, a square quadrupole, a hexapole, an octopole, a stacked ring ion guide, an ion funnel, an ion carpet, or any combination thereof.
11. The method of claim 9 wherein calculating an effective r0 is based on the observed low mass cutoff, a nominal r0, and an expected low mass cutoff.
12. The method of claim 11 wherein calculating the effective r0 is in accordance with
r
0
effective
=
K
observed
*
r
0
nominal
2
/
K
expected
the expected value for a parameter and K observed is the observed value for the parameter, the parameter selected from q, q*(m/z), q*(m/z)*ω 2 , q*(m/z)*f 2 , V, V/ω 2 , V/f 2 , or a combination thereof.
13. The method of claim 11 wherein calculating the effective r0 is in accordance with
r
0
effective
=
cutoff
observed
*
r
0
nominal
2
/
cutoff
expected
.
14. The method of claim 9 wherein the observed low mass cutoff is an average across at least two calibrant ion species.
15. The method of claim 9 wherein the RF voltage is determined based on the effective r0, the RF frequency, and a tune table.
16. The method of claim 15 wherein the tune table includes optimum q values for mass-to-charge ratios.
17. A non-transitory computer readable medium containing instructions that when implemented by a processor perform the steps of:
generating a tune curve for an ion guide;
determining a low mass cutoff for the ion guide from the tune curve;
calculating an effective r0 for the ion guide based on the observed low mass cutoff;
determining an RF voltage based on the effective r0 and the RF frequency;
applying the RF voltage to the ion guide; and
performing a mass analysis of ions in a sample.
18. The non-transitory computer readable medium of claim 17 wherein the ion guide is a quadrupole, a square quadrupole, a hexapole, an octopole, a stacked ring ion guide, an ion funnel, an ion carpet, or any combination thereof.
19. The non-transitory computer readable medium of claim 17 wherein the instructions to calculate the effective r0 are based on the observed low mass cutoff, a nominal r0, and an expected low mass cutoff.
20. The non-transitory computer readable medium of claim 19 wherein the instructions to calculate the effective r0 are in accordance with
r
0
effective
=
K
observed
*
r
0
nominal
2
/
K
expected
where K expected is the expected value for a parameter and K observed is the observed value for the parameter, the parameter selected from q, q*(m/z), q*(m/z)*ω 2 , q*(m/z)*f 2 , V, V/ω 2 , V/f 2 , or a combination thereof.
21. The non-transitory computer readable medium of claim 19 wherein the instructions to calculate the effective r0 are in accordance with
r
0
effective
=
cutoff
observed
*
r
0
nominal
2
/
cutoff
expected
.
22. The non-transitory computer readable medium of claim 17 wherein the observed low mass cutoff is an average across at least two calibrant ion species.
23. The non-transitory computer readable medium of claim 17 wherein the RF voltage is determined based on the effective r0, the RF frequency, and a tune table.