Shimadzu Corporation

Kazuo Mukaibatake

Daisuke Okumura

Shiro Mizutani

Shigenobu Nakano

Minoru Fujimoto

Hiroto Itoi

Shuichi Kawana

Wataru Fukui

Masahiro Kojima

Mitsuaki Fukuda

In a scan measurement in which a mass scan is repeated across a predetermined mass range, when a voltage is returned from a termination voltage of one scan to an initiation voltage for the next scan, an undershoot or other drawbacks occur to destabilize the voltage value. Therefore, an appropriate waiting time is required. Conventionally, this waiting time has been set to be constant regardless of the analysis conditions. On the other hand, in the quadrupole mass spectrometer according to the present invention, the mass difference &#x394;M between the scan termination mass and the scan initiation mass is computed based on the specified mass range, and a different settling time is set in accordance with this mass difference. When the mass difference &#x394;M is small and hence requires only a short voltage stabilization time, a relatively short settling time is set. This shortens the cycle period of the mass scan, which increases the temporal resolution.

Quadrupole mass spectrometer with quadrupole mass filter as a mass separator

An ionization chamberis provided between a liquid chromatograph unitand a mass spectrometer, and is formed of: an atomization means; and an ion introducing pipeof which the entrance portion is created within the ionization chamberin the horizontal direction that is perpendicular to the Z direction and of which the exit portion is created within the mass spectrometer unit. A liquid sample that has been fed from the liquid chromatograph unitis sprayed in the Z direction by the atomization meanswhile being ionized within the ionization chamber, wherein the entrance portion has an opening in such a form that corresponds to the spread in the XY plane of the liquid sample sprayed in the Z direction. The sprayed liquid sample is then fed into the mass spectrometer unitwhile being desolvated, which effectively contributes to analysis.

Ionization chamber

The larger an m/z to be adjusted, the wider a peak width which represents change in intensity in relation to change in voltage. This allows voltage step size to be increased during a search for an optimum voltage without overlooking a maximum intensity. Thus, a relational expression which gives a narrow voltage step size for a low m/z and gives a wide voltage step size for a high m/z is prestored in a voltage step information storage unit (), an optimum voltage adjustment controller () finds an optimum voltage step size for the m/z to be adjusted, during automatic voltage adjustment using the stored information, and controls a power supply unitso as to change a voltage applied to a first ion guide () stepwise. Ion intensity obtained each time the applied voltage changes is determined, and a voltage value which gives a maximum ion intensity is found and stored in an optimum voltage information storage unit (). Consequently, during automatic adjustment of a voltage applied to an ion transport optical element such as an ion guide, the time required for the adjustment can be reduced without overlooking an optimum voltage value which gives a maximum ion intensity.

Mass spectrometer

In an MS unit, both an intensity of an ion having the highest intensity among the ions originating from a compound as the target of quantitative determination and an intensity of an isotopic ion are measured. A saturation detector determines whether or not digital data produced by an A/D converter from ion-intensity signals have reached a saturation level. A data selection controller selects the ion-intensity data showing the highest intensity when the signal is not saturated or the intensity data of the isotopic ion when the saturation has occurred or is probable to occur. When the latter data is selected, an ion intensity converter converts the intensity data into values corresponding to the intensity data of the highest-intensity ion by multiplying the intensity data by a factor calculated from a known isotopic abundance ratio.

Quantitative analysis method using mass spectrometer

In a first-stage intermediate vacuum chamber, cluster ions causing a background noise are dominantly formed in area (A), while fragment ions are dominantly generated in area (B). Taking this fact into account, when no in-source CID analysis is performed, voltages applied to the first-stage plate electrode of an ion guide and the exit end of a desolvation tube are adjusted to create an accelerating electric field only in area (A) without creating such a field in area (B). Meanwhile, voltages applied to the electrodes of the ion guide are adjusted to create an electric field for separating ions according to their mobility and selecting a specific ion. Such an operation suppresses the cluster-ion formation, removes ions which originate from impurities and have mass-to-charge ratios close to or equal to those of the ions originating from a target substance, and suppresses the fragment-ion generation. As a result, the target ions are detected with high S/N.

Atmospheric pressure ionization mass spectrometer

When an SIM measurement for ions originating from a target component separated by a chromatograph is performed, the measurement is performed while the mass-resolving power is switched among a plurality of levels of resolving power, with the mass-to-charge ratio fixed at a target value (S), and an extracted ion chromatogram is created based on each of data obtained corresponding to respective mass-resolving powers (S). After the extracted ion chromatograms are obtained, an S/N ratio is calculated for a peak of the target component on each of the chromatograms (S), and a mass-resolving power which yields the highest S/N ratio is selected (S). The selected mass-resolving power is set as the mass-resolving power in the subsequent measurements of the same target component in the same kind of sample (S), and the quantitative determination of the target component is performed using the extracted ion chromatogram obtained with the selected mass-resolving power (S).

Chromatograph mass spectrometer

In a first-stage intermediate vacuum chamber, cluster ions causing a background noise are dominantly formed in area (A), while fragment ions are dominantly generated in area (B). Taking this fact into account, in an in-source CID analysis mode, a DC voltage higher than that applied to a skimmer is applied to a first ion guide so as to create an accelerating electric field in area (B), whereby the ions are sufficiently energized to promote the fragmentation. When the in-source CID is not performed, a DC voltage higher than that applied to the first ion guide is applied to the exit end of a desolvation tube so as to create an accelerating electric field only in area (A) without creating such a field in area (B), whereby both the formation of the cluster ions and the generation of the fragment ions are suppressed, so that a high-quality chromatogram can be obtained.

A table () for relating an appropriate DC bias voltage to each of a plurality of selectable scan speeds is stored beforehand in an auto-tuning data memory section (). In an auto-tuning operation, a controller () determines the DC bias voltage corresponding to each scan speed by referring to the table () and fixes the output of an ion-drawing voltage generator () at that voltage. Subsequently, while changing the voltages applied to relevant sections such as an ion optical system (), the controller () finds voltage conditions under which the detection signal is maximized. The conditions thus found are stored in an auto-tuning result data (). In an analysis of a target sample, a DC bias voltage corresponding to a scan speed specified by an operator is obtained from the DC bias voltage table (), and the optimal conditions for this voltage are obtained from the auto-tuning result data (). Based on these items of information, conditions for the scan measurement are determined. This method prevents the deterioration in detection sensitivity, which will otherwise take place if the scan measurement is performed at a high scan speed.

Quadrupole mass spectrometer

The present invention aims at suppressing noises when a mass analysis is performed by introducing a sample solution into an atmospheric pressure ion source by a pressurized liquid feeding method. As a dilution solvent of the sample solution contained in a sample container, a mixed liquid is used in which the mixture ratio of an organic solvent such as methanol is decreased to 20% and the ratio of water is 80%. Since nitrogen, which is a gas for the pressurization, is soluble in an organic solvent, decreasing the ratio of the organic solvent lowers the saturated dissolution amount and suppresses unstable emergence of the gas in the process of the mass analysis. Consequently, even after the elapse of a considerable length of time from the start of liquid feeding, spike-like noises do not appear in the ion intensity, which stabilizes the ion intensity.

Method of atmospheric pressure ionization for mass spectrometer

An object of the present invention is to provide a mass spectrometer having an optical ion transport system where the efficiency for generating and converting fragment ions can be increased, and which can transport the generated fragment ions efficiently to the rear stage, and in order to achieve this object, the mass spectrometer for ionizing a sample in an ionization chamberand drawing the ionized sample into a mass spectrometric chamberis provided with an ion transport optical system having electrodes-and-provided so as to surround an optical ion axis, and is characterized in that the above described electrodes-and-have an inclined surface which is inclined so as to spread in the direction in which ions progress along the above described optical ion axis.

The direct current bias voltage to be applied to the pre-filter provided in the previous stage of the quadrupole mass filter for selecting an ion according to the mass-to-charge ratio is changed in accordance with the mass-to-charge ratio of the target ion to be allowed to pass through, in order that the time period required for an ion to pass through the pre-filter is uniformed regardless of the mass-to-charge ratio, and simultaneously the phase of the oscillation of ions at the entrance of the quadrupole mass filter is also uniformed. In the range where the mass-to-charge ratio is larger than some degree, the ion's oscillation itself is small, and in addition, the ion's passage efficiency deteriorates rather than enhances, due to the potential barrier created by the voltage difference from the direct current bias voltage applied to the quadrupole mass filter.

If a scanning rate of a mass scanning is set to be high, the amount of change in an applied voltage between a time of an incidence of a certain ion into a quadrupole mass filter and a time of an emission of the ion therefrom increases. This leads to a change in the condition of a passage of ions, causing the amount of ions to decrease and thereby deteriorating detection sensitivity. In order to avoid this problem, according to the present invention, the values of direct current voltage U and an amplitude V of radio-frequency voltage, both voltages being applied to rod electrodes during a mass scanning, are respectively determined so that a voltage ratio U/V of the voltage U to the amplitude V becomes smaller as the scanning rate becomes higher. Accordingly, in a stability diagram based on the Mathieu equation, the inclination of line L indicating the change in the applied voltage during the mass scanning becomes gradual and the amount of ions passing through the quadrupole mass filter increases particularly when the mass is high.

Quadropole mass spectrometer

The length of the collision cell () in the direction along the ion optical axis (C) is set to be within the range between 40 and 80 mm, and typically 51 mm, which is remarkably shorter than before. The CID gas is supplied so that it flows in the direction opposite to the ion's traveling direction. Since the energy that an ion receives in colliding with a CID gas increases, it is possible to practically and sufficiently ensure the CID efficiency even though the collision cell () is short. In addition, since the passage distance for an ion is short, the passage time is shortened. Accordingly, it is possible to avoid the degradation in the detection sensitivity and the generation of a ghost peak due to the delay of the ion.

Collision cell for an MS/MS mass spectrometer

In conventional mass spectrometers, if ions are converged by a radio-frequency electric field under the condition of relatively high gas pressure, the ions are decelerated and are delayed, or stagnated in an extreme case, to cause a decrease in the detection sensitivity or an appearance of a ghost peak. By contrast, in the mass spectrometer according to the present invention, lens electrodescomprises four plate-shaped electrodesthrough, which are radially arranged around the ion optical axis C at intervals of 90 degrees from each other; the four electrodes placed in the plane being approximately perpendicular to the ion optical axis C form a group, and a plurality of the groups are arranged along the ion optical axis C direction at approximately even intervals. The radio-frequency voltages each applied to each of any pair of electrodes adjacent along the direction of the ion optical axis C have a given amount of phase shift. With this configuration, when ions enter the lens electrode, an ion acceleration effect is exerted in accordance with the amount of phase shift of the adjacent radio-frequency electric fields, and the ions are sequentially accelerated as they travel through the lens electrode. Consequently, a delay or stagnation of the ions can be avoided.

Growing community of inventors

Kyoto, Japan

Kazuo Mukaibatake