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JEOL : Patent Issued for Mass Spectrometer and Method of Adjusting Same (USPTO 9373493)

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07/01/2016 | 09:03am CEST

By a News Reporter-Staff News Editor at Journal of Engineering -- A patent by the inventor Kou, Junkei (Tokyo, JP), filed on November 20, 2013, was published online on June 21, 2016, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 9373493 is assigned to JEOL Ltd. (Tokyo, JP).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to a mass spectrometer and method of adjusting it.

"A quadrupole mass spectrometer is an instrument which has a quadrupole mass filter generating a hyperbolic electric field and which operates to produce a selecting voltage by superimposing an RF voltage and a DC voltage on each other and to pass ions of only a desired mass-to-charge ratio by applying the selecting voltage and an axial voltage (that is a DC offset voltage applied to the four quadrupole electrodes equally). If only the RF voltage and axial voltage are applied to the quadrupole mass filter, this filter acts as an ion guide that passes all ions of a certain mass-to-charge ratio or higher. A triple quadrupole mass spectrometer is built by coupling two quadrupole mass filters and mounting a collision cell between them. Since the triple quadrupole mass spectrometer has two mass analyzers, this mass spectrometer provides higher ion selectivity than a single quadrupole mass spectrometer and thus is often used in quantitative and qualitative analysis.

"In a triple quadrupole mass spectrometer, desired ions are first selected by the first mass analyzer. The ions selected by the first mass analyzer are normally known as precursor ions and guided into a collision cell including a multipole ion guide. An entrance electrode and an exit electrode are disposed on opposite sides of the ion guide. The ion guide has means (such as a needle valve) for introducing a gas from the outside. If a gas is introduced into the collision cell, precursor ions collide against the collision gas, producing fragmentation with a certain probability. As a result, the precursor ions are fragmented in the collision cell. These fragmented ions are known as product ions. Only intended ions of the precursor ions and the product ions in the collision cell are separated by the second mass analyzer and detected.

"Sometimes, ion cooling is done on the upstream side of the first mass analyzer. In the cooling, ions are normally caused to collide with a gas by a multipole ion guide. The collision with the gas lowers the average kinetic energy of the ions and also reduces the range of kinetic energies. The cooling makes uniform the velocities of ions about to enter the first mass analyzer. This leads to improvements of resolution and sensitivity.

"When quantitative analysis is performed, triple quadrupole mass spectrometers are often used in a mode known as multiple reaction monitoring (MRM). In this mode, ions of certain mass-to-charge ratios are selected by the first mass analyzer and the second mass analyzer, respectively. One measurement in which different ions are selected by the first and second mass analyzers is known as a transition. Transitions which are different in combination of selected ions are carried out in turn. Transitions performed in succession may interfere with each other. For example, if ions generated by a previous transition are left in the collision cell, and if the next transition is performed, then it is impossible to know which of the transitions produced the detected ions. In order to carry out multiple reaction monitoring (MRM) with reliable results, it is desired that ions in the collision cell be ejected as much as possible whenever the transition is varied.

"JP-A-2010-127714 sets forth a method of accomplishing high sensitivity of the instrument by temporarily storing ions in a collision cell and then ejecting the ions. Since the ejected ions are pulsed, acceptance of noises is suppressed by accumulating pulsed portions as signals. In this way, the sensitivity of the instrument can be improved.

"Even in this triple quadrupole mass spectrometer where ions are stored in the collision cell, it is important to eject ions from the collision cell as much as possible whenever the transition is varied. To reduce interference between transitions, the opening time in which ions are ejected should be increased. However, if the opening time of the collision cell is lengthened, high-speed multiple reaction monitoring can no longer be achieved. In this way, the opening time should not be too short or too long. The opening time needs to be optimized according to the tolerable range of interference between transitions."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "In view of the foregoing problem, the present invention has been made. According to some aspects of the invention, it is possible to offer a mass spectrometer and mass spectrometer adjusting method capable of optimizing the time for which a collision cell is opened.

"(1) A mass spectrometer associated with the present invention has: an ion source for ionizing a sample; a first mass analyzer for selecting first desired ions from the ions generated in the ion source according to mass-to-charge ratio; a collision cell for fragmenting some or all of the first desired ions into product ions; a second mass analyzer for selecting second desired ions from the first desired ions and the product ions according to mass-to-charge ratio; a detector for detecting the second desired ions; and a control section for controlling the collision cell in such a way that the cell performs a storing operation for storing the first desired ions and the product ions for a given storage time and then performs an opening operation for ejecting the stored ions for a given opening time. In an adjustment mode, the control section adjusts the opening time based on information about settings.

"In this mass spectrometer associated with the present invention, the adjustment mode is introduced to adjust the opening time of the collision cell based on the information about the settings, whereby the opening time of the collision cell can be optimized.

"(2) In one feature of this mass spectrometer, the collision cell has an entrance and an exit. The control section may cause the collision cell to perform the storing operation by opening the entrance of the cell and closing the exit of the cell. The control section may cause the collision cell to perform the opening operation by closing the entrance of the cell and opening the exit of the cell.

"(3) In another feature of this mass spectrometer, the information about the settings may indicate a target value of the ratio of the amount of the second desired ions ejected from the collision cell by the opening operation to the amount of the second desired ions stored in the collision cell immediately prior to the opening operation.

"In this mass spectrometer, the opening time can be optimized according to the tolerable range of interference between transitions by searching for and finding a value of the opening time that brings the ratio of the intensity of ions ejected from the collision cell closest to a target value.

"(4) In a further feature of this mass spectrometer, in the adjustment mode, the control section may cause the collision cell to perform the opening operation plural times whenever the storing operation is performed once, measure the amount of the second desired ions ejected from the collision cell by the opening operation performed first in response to a detection signal from the detector while varying the opening time during the opening operation performed first after the storing operation and the amount of the second desired ions ejected from the collision cell by performing the opening operation plural times, and calculate a value of the opening time at which the ratio of these two measured amounts is closest to the target value.

"According to this mass spectrometer, almost all of the ions stored in the collision cell can be ejected by performing the opening operation plural times whenever the collision cell performs the storing operation once. Therefore, the ratio of the intensity of ions ejected by the opening operation performed first after the storing operation can be calculated from the ratio of the total amount of ions ejected by performing the opening operation plural times to the amount of ions ejected by performing the opening operation for the first time after the storing operation.

"(5) In a still other feature of this mass spectrometer, the information about the settings may indicate a target value of the amount of the second desired ions ejected from the collision cell by the opening operation.

"According to this mass spectrometer, the opening time can be optimized according to the tolerable range of interference between transitions by searching for and finding a value of the opening time at which the intensity of ejected ions is closest to a target value.

"(6) In a yet other feature of this mass spectrometer, in the adjustment mode, the control section may measure the amount of the second desired ions ejected from the collision cell by the opening operation in response to the detection signal from the detector while varying the opening time and calculate a value of the opening time at which the measured amount is closest to the target value.

"According to this mass spectrometer associated with the present invention, the intensity of the ejected ions during the opening operation after the storing operation can be calculated from the amount of ions ejected by the opening operation performed for the first time after the storing operation of the collision cell.

"(7) In an additional feature of this mass spectrometer, the control section may provide control to maintain the storage time constant.

"According to this mass spectrometer associated with the present invention, the amount of ions stored in the collision cell can be kept constant by maintaining constant the storage time for the collision cell.

"(8) In a still further feature of this mass spectrometer, the control section may provide control such that at least one of the first and second mass analyzers acts as an ion guide.

"In this mass spectrometer associated with the present invention, ion intensities can be measured at high sensitivity by operating at least one of the first and second mass analyzers as an ion guide. This improves the accuracy at which the opening time of the collision cell is adjusted.

"(9) In a yet additional feature of this mass spectrometer associated with the present invention, there is further provided a cooling chamber mounted between the ion source and the first mass analyzer to lower kinetic energies of the ions generated in the ion source. The control section may provide control such that the cooling chamber performs a storing operation for temporarily storing the ions generated in the ion source and then performs an opening operation for ejecting the stored ions.

"In this mass spectrometer associated with the present invention, pulsed ions are generated in the cooling chamber. Consequently, ion intensities can be measured at high sensitivity. This improves the accuracy at which the opening time of the collision cell is adjusted.

"(10) In a still additional feature of this mass spectrometer, the control section may cause the cooling chamber to perform the storing operation by keeping the entrance of the cooling chamber open and closing the exit of the cooling chamber and cause the cooling chamber to perform the opening operation by opening the exit of the cooling chamber.

"(11) In another feature of this mass spectrometer, the control section may provide control such that the storing operation and the opening operation are carried out for given times by the cooling chamber.

"In this mass spectrometer associated with the present invention, the amount of ions entering the collision cell can be maintained constant by maintaining constant the storage time and the opening time of the cooling chamber.

"(12) In a further feature of this mass spectrometer, in the adjustment mode, the control section may calculate the opening time according to the information about the settings for each mass-to-charge ratio of the second desired ions, produce information indicating corresponding relationships between mass-to-charge ratios of the second desired ions and set values of the opening time based on the calculated opening times, and record the produced information.

"(13) In a still additional feature of this mass spectrometer, in a measurement mode, the control section may set the opening time according to the mass-to-charge ratios of the selected second desired ions based on the information indicating the corresponding relationships.

"In this mass spectrometer associated with the present invention, the opening time of the collision cell can be optimized for each transition even if an actual sample is measured by interpolating or extrapolating the relationship between the mass-to-charge ratio of the second desired ions and set values of the opening time.

"(14) In a still further feature of this mass spectrometer, at least one of the first and second mass analyzers may include a quadrupole mass filter.

"(15) An adjustment method associated with the present invention is implemented in a mass spectrometer which has: an ion source for ionizing a sample; a first mass analyzer for selecting first desired ions from the ions generated in the ion source according to mass-to-charge ratio; a collision cell for fragmenting some or all of the first desired ions into product ions; a second mass analyzer for selecting second desired ions from the first desired ions and the product ions according to mass-to-charge ratio; a detector for detecting the second desired ions; and a control section for controlling the collision cell in such a way that the cell performs a storing operation for storing the first desired ions and the product ions for a given storage time and then performs an opening operation for ejecting the stored ions for a given opening time. The method starts with measuring the amount of the second desired ions ejected from the collision cell by the opening operation while varying the opening time. This is herein referred to as the first measuring step. The amount of the second desired ions stored in the collision cell immediately prior to the opening operation of the first measuring step is measured. This is herein referred to as the second measuring step. During each opening time, an 'ejected ion intensity ratio', which is defined to be the ratio of the amount measured by the first measuring step to the amount measured by the second measuring step, is calculated. A value of the opening time at which the ejected ion intensity ratio is closest to a target value is calculated based on the calculated ejected ion intensity ratio.

"According to this mass spectrometer associated with the present invention, the opening time can be optimized according to the tolerable range of interference between transitions by searching for and finding a value of the opening time at which the ratio of the intensity of ions ejected from the collision cell is closest to a target value.

"(16) Another adjustment method associated with the present invention is implemented in a mass spectrometer which has: an ion source for ionizing a sample; a first mass analyzer for selecting first desired ions from the ions generated in the ion source according to mass-to-charge ratio; a collision cell for fragmenting some or all of the first desired ions into product ions; a second mass analyzer for selecting second desired ions from the first desired ions and the product ions according to mass-to-charge ratio; a detector for detecting the second desired ions; and a control section for controlling the collision cell in such a way that the cell performs a storing operation for storing the first desired ions and the product ions for a given storage time and then performs an opening operation for ejecting the stored ions for a given opening time. The adjustment method starts with measuring the amount of the second desired ions ejected from the collision cell by the opening operation while varying the opening time. Then, a value of the opening time at which the amount of the second desired ions ejected from the collision cell by the opening operation is closest to a target value is calculated, based on the measured amount of the second desired ions.

"This mass spectrometer adjusting method associated with the present invention makes it possible to optimize the opening time according to the tolerable range of interference between transitions by searching for and finding the value of the opening time at which the intensity of the ions ejected from the collision cell is closest to the target value."

URL and more information on this patent, see: Kou, Junkei. Mass Spectrometer and Method of Adjusting Same. U.S. Patent Number 9373493, filed November 20, 2013, and published online on June 21, 2016. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=9373493.PN.&OS=PN/9373493RS=PN/9373493

Keywords for this news article include: JEOL Ltd., Technology Companies, Scientific and Technical Instrument Companies.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2016, NewsRx LLC

(c) 2016 NewsRx LLC, source Science Newsletters

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