Reduction of chemical noise in a MALDI mass spectrometer by in-trap photodissociation of matrix cluster ions
AssigneeThermo Finnigan LLC
InventorViatcheslav V. Kovtoun
Life of this patent
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Abstract
A MALDI mass spectrometer includes a radiation source, such as a gas or solid state laser, that emits a beam of radiation (typically in the UV or IR wavelengths) directed along the central axis of a linear ion trap in which analyte ions and matrix cluster ions are confined. The radiation beam has a wavelength that is strongly absorbed by the matrix cluster ions. The absorption of radiation by the matrix cluster ions produces dissociation of the matrix cluster ion into fragments having mass-to-charge ratios that lie below a mass-to-charge ratio range of interest. Thus, chemical noise associated with matrix cluster ions is reduced or eliminated.
Claims15
A mass spectrometer, comprising:
- a matrix-assisted laser desorption and ionization (MALDI) source for producing ions by irradiating a sample;
- a two-dimensional ion trap having an interior into which at least a portion of the ions are admitted, the ions including analyte ions and matrix cluster ions, the ions occupying an ion cloud;
- and
- a radiation source for generating a beam of radiation that overlaps with the ion cloud, the radiation having a frequency that is strongly absorbed by the matrix cluster ions such that at least a portion of the matrix cluster ions undergo dissociation;
- wherein the linear ion trap is further configured to generate a supplemental oscillating field that causes the analyte ions, but not the matrix cluster ions, to travel outside of the radiation beam.
A mass spectrometer, comprising:
- a matrix-assisted laser desorption and ionization (MALDI) source for producing ions by irradiating a sample;
- a two-dimensional ion trap having an interior into which at least a portion of the ions are admitted, the ions including analyte ions and matrix cluster ions, the ions occupying an ion cloud;
- a radiation source for generating a beam of radiation that overlaps with the ion cloud, the radiation having a frequency that is strongly absorbed by the matrix cluster ions such that at least a portion of the matrix cluster ions undergo dissociation;
- and
- a beam switching element positioned in the radiation beam configured to controllably switch the radiation beam between first and second beam paths, the first beam path terminating at the sample for producing ions therefrom, and the second beam path overlapping the ion cloud.
A method for reducing chemical noise in a MALDI mass spectrometer, comprising the steps of:
- producing ions by irradiating a sample containing an analyte and a matrix;
- admitting the ions into the interior of a two-dimensional ion trap, the ions occupying an ion cloud and including analyte ions and matrix cluster ions;
- irradiating the matrix cluster ions with a beam of radiation directed along the interior of the ion trap to cause at least a portion of the matrix cluster ions to dissociate into fragments;
- and
- generating a supplemental electric field within the ion trap to cause the analyte ions, but not the matrix cluster ions, to travel outside of the radiation beam.
A method of reducing chemical noise in a MALDI mass spectrometer, comprising the steps of:
- producing ions by irradiating a sample containing an analyte and a matrix;
- admitting the ions into the interior of a two-dimensional ion trap, the ions occupying an ion cloud and including analyte ions and matrix cluster ions;
- irradiating the matrix cluster ions with a beam of radiation directed along the interior of the ion trap to cause at least a portion of the matrix cluster ions to dissociate into fragments;
- and
- controllably switching the radiation beam between a first beam path tenninating at the sample, and a second beam path extending along the interior of the ion trap.
A mass spectrometer, comprising:
- a matrix-assisted laser desorption and ionization (MALDI) source for producing ions by irradiating a sample;
- a two-dimensional ion trap having an interior into which at least a portion of the ions are admitted, the ions including analyte ions and matrix cluster ions, the ions occupying an ion cloud;
- and a radiation source for generating a beam of radiation that overlaps with the ion cloud, the radiation having a frequency that is strongly absorbed by the matrix cluster ions and not absorbed or weakly absorbed by the analyte ions, such that at least a portion of the matrix cluster ions undergo dissociation without substantial dissociation of the analyte ions wherein the efficiency of trapping of ions within the interior of the ion trap is not adversely affected by absorption of the radiation beam by the analyte ions.
Dependencies are inferred from the claim text.