# US 2014/0151544 A1 · Exponential Scan Mode for Quadrupole Mass Spectrometers to Generate Super-Resolved Mass Spectra

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- Number: US 2014/0151544 A1
- Document ID: US20140151544A1
- Status: Published application
- Kind: A1
- Application number: 14/014,844
- Filed: 2013-08-30
- Published: 2014-06-05
- Earliest claimed: 2012-11-30
- Assignees: Thermo Finnigan LLC
- Applicants: Thermo Finnigan LLC
- Inventors: Robert A. GROTHE, Jr.
- Web page: https://patentgrep.com/patent/US20140151544A1

## CPC

- H01J 49/4215: {Quadrupole mass filters (H01J49/4225 takes precedence)}
- H01J 49/0031: {Step by step routines describing the use of the apparatus (H01J49/0081 takes precedence)}
- H01J 49/4225: {Multipole linear ion traps, e.g. quadrupoles, hexapoles}
- H01J 49/429: {Scanning an electric parameter, e.g. voltage amplitude or frequency}
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

A novel scanning method of a mass spectrometer apparatus is introduced so as to relate by simple time shifts, rather than time dilations, the component signal (“peak”) from each ion even to an arbitrary reference signal produced by a desired homogeneous population of ions. Such a method and system, as introduced herein, is enabled in a novel fashion by scanning exponentially the RF and DC voltages on a quadrupole mass filter versus time while maintaining the RF and DC in constant proportion to each other. In such a novel mode of operation, ion intensity as a function of time is the convolution of a fixed peak shape response with the underlying (unknown) distribution of discrete mass-to-charge ratios (mass spectrum). As a result, the mass distribution can be reconstructed by deconvolution, producing a mass spectrum with enhanced sensitivity and mass resolving power.

## Claims

### Claim 1

A mass spectrometer, comprising:
a quadrupole configured so that an exponentially ramped oscillatory (RF) voltage and an exponentially ramped direct current (DC) voltage can be applied to a set of electrodes of the device, said (RF) and (DC) voltages being applied exponentially versus time and maintained in constant proportion to each other during the progression of ramping, thus enabling said quadrupole to selectively transmit to its distal end an abundance of ions within a range of mass-to-charge values (m/z's) determined by the amplitudes of said applied voltages;
a detector configured adjacent to the distal end of said quadrupole to acquire a series of said abundance of ions during the progression of said applied exponential ramped oscillatory (RF) and direct current (DC) voltages; and
a processor coupled to said detector and configured to subject said acquired series of said abundance of ions to deconvolution as a function of the applied exponential (RF) and/or (DC) fields so as to provide a mass spectrum.

### Claim 2 (depends on 1)

The mass spectrometer of claim 1, wherein said applied exponentially ramped oscillatory (RF) voltage and said applied exponentially ramped direct current (DC) voltages are not maintained in constant proportion to each other during the progression of ramping.

### Claim 3 (depends on 1)

The mass spectrometer of claim 1, wherein said detector comprises a single detector.

### Claim 4 (depends on 1)

The mass spectrometer of claim 1, wherein said detector comprises a two-dimensional array.

### Claim 5 (depends on 1)

The mass spectrometer of claim 1, wherein said processor is configured to subject said acquired series of said abundance of ions to deconvolution based on temporally-resolved information and/or temporally and spatially resolved ion information as provided by said detector.

### Claim 6 (depends on 1)

The mass spectrometer of claim 1, wherein said processor is configured to deconvolve data in the series of ion images with a single reference signal, said reference signal being representative of a measured single ion species at a particular operating state of the multipole.

### Claim 7 (depends on 1)

The mass spectrometer of claim 1, wherein the processor is configured to deconvolve data in the series of ion images with a set of a plurality of reference signals, said plurality of reference signals each being representative of a measured or an expected spatial distribution of a single ion species at a particular operating state of the multipole.

### Claim 8 (depends on 1)

The mass spectrometer of claim 1, further comprising a collision cell positioned upstream in an ion path relative to an inlet end of said quadrupole

### Claim 9 (depends on 1)

The mass spectrometer of claim 1, wherein the amplitudes of the oscillatory and DC voltages are selected to set an m/z range of the transmitted ions of between 1 and 300 AMU.

### Claim 10 (depends on 1)

The mass spectrometer of claim 1, wherein said quadrupole is configured as an ion trap.

### Claim 11

A mass spectrometer method, comprising:
measuring by way of a quadrupole, a reference signal representative of a measured or expected time distribution and/or time and spatial distribution of a single ion species while time-varying RF and DC voltages are applied to said quadrupole;
applying an exponentially ramped oscillatory (RF) voltage and an exponentially ramped direct current (DC) voltage to said quadrupole, wherein said RF and DC voltages are maintained in constant proportion to each other during the progression of ramping so as to selectively transmit to the distal end of said quadrupole, an abundance of ions to be measured within a range of mass-to-charge values (m/z's) determined by the amplitudes of said applied (RF) and (DC) voltages;
acquiring temporal or both temporal and spatial measurements of the abundance of ions from the distal end of said quadrupole;
reconstructing a mass spectrum by deconvolving said reference signal from the acquired ion measurements, thus providing estimates of ion abundance at regular time intervals;
transforming the time points where estimates were provided into mass-to-charge ratios, thereby forming a (sampled) mass spectrum; and
and reconstructing a list of distinct m/z values and estimated intensities from the deconvolved mass spectrum.

### Claim 12 (depends on 11)

The method of claim 11, wherein the applying step of said RF and DC voltages comprises: applying said RF and DC voltages but in non-constant proportion to each other during the progression of ramping.

### Claim 13 (depends on 11)

The method of claim 11, wherein said computing step further comprises: generating a shifted autocorrelation vector from said reference signal.

### Claim 14 (depends on 11)

The method of claim 11, wherein said computing step further comprises: constructing a matrix form of said raw data from using said reference signal.

### Claim 15 (depends on 11)

The method of claim 11, where said matrix form is analyzed using Fourier Transform Mass Spectrometry (FTMS).

### Claim 16 (depends on 11)

The mass spectrometer method of claim 11, further comprising: providing an increased sensitivity from about 10 up to about 200 times by opening the stability boundaries defined by Mathieu (a, q) values.

### Claim 17 (depends on 11)

The mass spectrometer method of claim 11, wherein the step of applying said amplitudes of the oscillatory and DC voltages further comprises: selecting said voltages to set an m/z range of the transmitted ions of between 1 and 300 AMU.

### Claim 18 (depends on 11)

The mass spectrometer method of claim 11, wherein the step of applying said amplitudes of the oscillatory and DC voltages further comprises: selecting said voltages to set an m/z range of the transmitted ions of greater than 300 AMU.

### Claim 19 (depends on 11)

The mass spectrometer method of claim 11, wherein said reconstructing steps further comprises: mathematical deconvolution in the time domain, wherein the resultant values on the time axis are transformed to said distinct m/z values by exponentiation.

### Claim 20 (depends on 19)

The mass spectrometer method of claim 19, wherein said mathematical deconvolution includes Fast Fourier transforms.

### Claim 21 (depends on 11)

The mass spectrometer method of claim 11, wherein said method further comprises calibrating a coupled instrument that controls said ramped oscillatory (RF) voltage and said exponentially applied direct current (DC) voltage so that a desired scan line passes through the origin of a stability region.

### Claim 22 (depends on 11)

The mass spectrometer method of claim 11, wherein the step of measuring a reference signal further comprises: converting said reference signal for a known m/z value into a family of reference signals for a range of m/z values so as to compensate for non-idealities in the quadrupole field.

### Claim 23 (depends on 11)

The mass spectrometer method of claim 11, further comprising: providing for mass delta differentiation of 100 ppm down to about 10 ppm.