JPH05332994A - Mass spectrometry - Google Patents

Abstract

(57) [Summary] [Purpose] In a quadrupole mass spectrometer, the mass is represented by the quadrupole applied voltage, but when high-speed scanning is performed, the electrode applied voltage changes until ions are detected, and the displayed mass Error occurs. This error is corrected. [Structure] A mass calibration table is created by actual measurement using the scanning speed as a parameter, and correction is performed according to the scanning speed using this dave during analysis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quadrupole mass spectrometer suitable for performing high speed mass scanning.

[0002]

2. Description of the Related Art In a quadrupole mass spectrometer, the mass number of detected ions is proportional to the high-frequency voltage applied to the quadrupole electrode. The conversion formula that defines the relationship between the input digital data of the D / A converter that is set to and the mass of the detected ion is determined to obtain the mass of the detected ion.

As described above, in the quadrupole mass spectrometer, the mass number is determined by the high-frequency voltage applied to the quadrupole electrode, but the mass scanning speed is relatively slow, and the ions enter between the quadrupoles. Although the accurate mass value can be known as long as the change in the high-frequency pressure between the detection and the detection is negligible, when the scanning speed becomes high, the mass display shows that the ions have already passed between the quadrupoles. As a result of being performed according to the high frequency voltage at the time of being detected, a mass different from the actual mass is displayed.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to make it possible to obtain a correct mass number display even when high speed mass scanning is performed with a quadrupole mass spectrometer.

[0005]

[Means for Solving the Problem] Using a standard sample, mass spectrometry is performed at different scanning speeds to obtain the difference between the displayed mass and the actual amount, that is, the relationship between the mass correction value and the scanning speed, and use the relationship. Then, the correct mass was determined from the scanning speed and the displayed mass during actual analysis.

[0006]

[Function] Since the ions incident on the mass spectrometer are accelerated by a constant acceleration voltage, the kinetic energy is constant regardless of the mass. Therefore, the velocity of the ions slows in inverse proportion to the square root of the mass m. The difference between the displayed mass and the actual amount of detected ions is proportional to the change in the high-frequency voltage between the time when the ions are incident on the quadrupole electrode and the time when they are detected. This change has a slow ion velocity. Assuming that the mass scanning speed is S (mass number / time), the displayed mass of detected ions is m, and the difference between the displayed mass and the actual amount, that is, the correction value is ΔM, ΔM = KS√m Therefore, the correction value for the displayed mass at the scanning speed S can be known by actually determining the proportional constant K.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart of an analysis operation by a quadrupole mass spectrometer which carries out the method of the present invention. FIG. 2 shows the configuration of the quadrupole mass spectrometer used in the above example. In FIG. 2, 1 is a quadrupole mass analysis unit, 2 is a sample ionization unit, 3 is an ion detection unit, 4 is a computer controlling the apparatus, and 5 is a high frequency voltage V applied to the quadrupole electrode. D / A converter, 6 is also a D / A converter for setting the DC voltage V, 7 is an A / D converter for A / D converting the ion detection signal, and 8 is a high frequency voltage mass conversion table and a correction data table. It is a memory for storing. Computer 4 has two D /
The digital data designating the high-frequency voltage V and the direct-current voltage V is output to the A converter, mass scanning is performed, the detection signal of the ion detector is taken in, and on the other hand, from the digital data designating V at the time of ion detection, The mass of the detected ion is determined using the table stored in the memory 8 and stored in the data memory 9 together with the ion detection signal.

The operation when mass spectrometry is performed using the above apparatus will be described with reference to the flowchart of FIG. First, low-speed mass scanning is performed using a standard sample, and the masses M1 and M
2, ... Mn ions are detected, and high-frequency voltage setting digital data D1, D2, ... When the peak center of each ion is detected
Dn is obtained, a high-frequency voltage-mass conversion table is created, and stored in the memory 8 (a). Next, high-speed scanning is performed at the scanning speed So using the same standard sample to detect each ion of the masses M1, M2, ... Mn, and high-frequency voltage setting digital data D1 ′, D2 ′ at the time of detecting the peak center of each ion. , ... Dn '
Ask for (b). Next, the above Di ′ (i = 1, 2, ... N)
From (a) to (c), the mass Mi ′ determined using the conversion table created in the step (b) is calculated, and the correction value ΔMi = Mi−M
i ′ is calculated (d), ΔM = KSo√ (Mi ′) is substituted for the above So, ΔMi ′ and Mi ′ to determine K, the mass Mi ′ obtained from the high frequency voltage mass conversion table and the correction value ΔM
A relationship table at the i-scan speed So is created and stored in the memory 8 (e). Finally, the actual sample is subjected to high-speed scanning at a scanning speed S, and the mass value M ′ obtained by the high-frequency voltage mass conversion table is multiplied by the correction value ΔM ′ obtained from the relationship table between the mass M ′ and the correction value ΔM, and S / So. Then, the correction value ΔM is calculated, and the actual amount M = M ′ + ΔM is calculated and stored (F) in the memory 9.

[0009]

The quadrupole mass spectrometer has an advantage that it can perform high speed scanning as compared with mass scanning by changing magnetic field strength in a magnetic field type mass spectrometer. However, according to the present invention, high speed scanning is performed. Since the error in the displayed mass of is corrected, accurate mass analysis can be performed by high-speed scanning. Since the mass error during high-speed scanning increases as the mass increases, the effect of the present invention is particularly great when performing high-speed analysis on a high-mass side or performing analysis over a wide mass range.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of an apparatus for executing the method of the present invention.

FIG. 2 is a flowchart of the operation of the above device.

[Explanation of symbols]

 1 mass spectrometric section 2 sample ionization section 3 ion detection section 4 control computer 5, 6 D / A converter 7 A / D converter 8 memory for storing conversion table 9 data memory

Claims (1)

[Claims] 1. A corrected mass value at a mass scanning speed S with respect to a mass value obtained from a voltage applied to a quadrupole electrode is obtained by using a standard sample, and is analyzed from a voltage applied to the quadrupole electrode at the time of actual sample analysis. A mass spectrometer method, characterized in that the obtained mass is corrected using the above correction value.