Tuning multipole RF amplitude for ions not present in calibrant

Patent metadata

Field	Value
Publication number	US-10056244-B1
Application number	US-201715662811-A
Country	US
Kind code	B1
Filing date	Jul 28, 2017
Priority date	Jul 28, 2017
Publication date	Aug 21, 2018
Grant date	Aug 21, 2018

Abstract

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.

First claim

What is claimed is:

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

*

Assignees

• Thermo Finnigan Llc

Inventors

• Quarmby Scott T
• Maze Joshua T
• Sanders Nathaniel L

Classifications

• H01J49/26

  Mass spectrometers or separator tubes · CPC title

• H01J49/0009 Primary

  Calibration of the apparatus · CPC title

• G01N27/62

  by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode · CPC title

• H01J49/062

  Ion guides (linear ion traps performing mass selection H01J49/4225, mass filters H01J49/421) · CPC title

• H01J49/0036

  Step by step routines describing the handling of the data generated during a measurement · CPC title