US 5,510,613 AGranted

Spatial-velocity correlation focusing in time-of-flight mass spectrometry

AssigneeIndiana University Foundation

InventorsJames P. Reilly, Steven M. Colby, Timothy B. King

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Abstract

An apparatus and method for minimizing ion peak width measurements in a time-of-flight mass spectrometer to thereby minimize the effects of initial ion position distributions and initial ion velocity distributions on the mass resolution of the spectrometer are provided. Where the ion source and ion generation geometries indicate a functional relationship between the initial ion position and initial ion velocity, this relationship is substituted into the time-of-flight equation and the instrument parameters are thereafter optimized to achieve minimization of ion peak width broadening. Experimental results using MALDI indicate reductions in ion peak widths of up to 96% over those observed with traditional MALDI techniques.

Claims19

Dependent claims

A time-of-flight mass spectrometer (TOFMS) for minimizing the effect on the TOFMS mass resolution of distributions in initial position and initial velocity of ions generated within the spectrometer, said TOFMS comprising:

a first grid connected to a first potential source for applying a first potential thereto;
a second grid juxtaposed with said first grid, said first and second grids defining a first region therebetween, said second grid being connected to a second potential source for applying a second potential thereto;
a sample source disposed within said first region for generating ions of various mass to charge ratios therefrom into said first region when said sample source is excited by external means, wherein the ions have an initial position distribution and an initial velocity distribution within said first region, and the initial position of each of the ions is a function of the initial velocity of the respective ion;
and
means for detecting the ions generated within said first region, said means for detecting being disposed remote from said second grid,
wherein said first and second potentials are applied to said first and second grids respectively at a predetermined time after the ions are generated within said first region to establish a first electric field of appropriate direction for accelerating the ions toward said means for detecting, the relative strengths of said first and second potentials and the predetermined time at which they are applied to said grids being chosen so that the time spread in the time of flight of ions of any particular mass to charge ratio generated within the first region to the means for detecting is minimized, thereby simultaneously minimizing the effect on the TOFMS mass resolution of the distributions in initial position and initial velocity of the ions generated within said first region.

3 more elements

A system for minimizing the effect of distributions in initial ion position and initial velocity on the mass resolution of a time-of-flight mass spectrometer (TOFMS), said system comprising:

a TOFMS having a sample source disposed within a sample region and an ion detector disposed a predetermined distance from said sample source;
means for generating ions of various mass to charge ratios from said sample source, wherein the generated ions have an initial position distribution and an initial velocity distribution within said sample region, and the initial position of each of the ions generated within said sample region is a function of the initial velocity of the respective ion;
means for establishing an electric field within said sample region of said TOFMS, said electric field accelerating the generated ions toward said ion detector;
and
means responsive to said ion generating means for triggering said electric field establishing means to establish said electric field a predetermined time after generating said ions,
wherein the strength of said electric field and the predetermined time period are chosen so that the time spread in the time of flight of generated ions of any particular mass to charge ratio to the means for detecting is minimized, thereby simultaneously minimizing the effect on the TOFMS mass resolution of the distributions in initial position and initial velocity of the generated ions.

3 more elements

Dependencies are inferred from the claim text.