Shimadzu Corporation

Aleksandr Rusinov

Li Ding

Sergey Smirnov

Apparatus and method for processing an image-charge/current signal for an ion(s) undergoing oscillatory motion within an ion analyser apparatus. The method comprises: obtaining a recording of the image-charge/current signal (-) in the time domain. Then, by a signal processing unit, a value for the period (T) of a periodic signal component is determined within the recorded signal. Subsequently, the recorded signal is segmented into a number of successive time segments [0;T] of duration corresponding to the period (T). These lime segments are then co-registered in a first time dimension (t) defining the period (T). The co-registered time segments are then separated along a second time dimension (t) transverse to the first time dimension (t). This generates a stack of time segments collectively defining a 2-dimensional (2D) function. The 2D function varies both across the stack in the first time dimension and along the stack in the second time dimension.

Time-frequency analysis

An apparatus configured to produce an image charge/current signal representative of trapped ions undergoing oscillatory motion. The apparatus includes: an electrostatic ion trap configured to trap ions such that the trapped ions undergo oscillatory motion in the electrostatic ion trap; an image charge/current detector configured to obtain an image charge/current signal representative of trapped ions undergoing oscillatory motion in the electrostatic ion trap, wherein the electrostatic ion trap configured to trap ions such that the image charge/current signal in the time domain repeats, for ions of a given mass/charge ratio m, at a frequency f(m) [Hz] with a signal period T(m) [s]. The image charge/current detector includes one or more pickup electrodes configured to obtain the image charge/current signal. The one or more pickup electrodes are arranged to detect two signal pulses caused by ions having the given mass/charge ratio m within each signal period T(m). The one or more pickup electrodes are further arranged such that the time separation &#x394;t(m) between the two signal pulses caused by ions having the given mass/charge ratio m within each signal period T(m) is approximately equal to 2p+1/2.n.f(m) so as to suppress a predetermined nth harmonic within the image charge/current signal, where n is an integer that is 1 or more, and where p is an integer that is 0 or more.

Apparatus configured to produce an image charge/current signal

A method of processing an image charge/current signal representative of trapped ions undergoing oscillatory motion. The method includes: identifying a plurality of fundamental frequencies potentially present in the image charge/current signal based on an analysis of peaks in a frequency spectrum corresponding to the image charge/current signal in the frequency domain, wherein each candidate fundamental frequency falls in a frequency range of interest; deriving a basis signal for each candidate fundamental frequency using a calibration signal; and estimating relative abundances of ions corresponding to the candidate fundamental frequencies by mapping the basis signals to the image charge/current signal. At least one candidate fundamental frequency is calculated using a frequency associated with a peak that falls outside the frequency range of interest and that has been determined as representing a second or higher order harmonic of the candidate fundamental frequency.

Method of processing an image charge/current signal

Disclosed is a method of quantification of one or more ion species, in a sample of ions, using a mass spectrometer, the method including the steps of:

Fourier transform mass spectrometry

A mass analyser comprises a pair of electrode arrays. Each array has a set of focusing electrodes which are supplied, in use, with voltage to create an electrostatic field in a space between the electrode arrays causing ions to undergo periodic, oscillatory motion in the space, ions passing between electrodes of the sets of focusing electrodes and being repeatedly focused at a center plane, mid-way between the electrode arrays. At least one electrode of each set of focusing electrodes has an electrode surface closer to the center plane than the electrode surfaces of other electrodes of the same set. The analyzer may be an ion trap mass analyser or a multi-turn ToF mass analyzer.

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Manchester, United Kingdom

Aleksandr Rusinov