JPH0562424B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a resolution adjustment device for a quadrupole mass spectrometer.

B. Prior Art In a quadrupole mass spectrometer, increasing the resolution lowers the sensitivity, and attempting to obtain higher sensitivity lowers the resolution. Therefore, the resolution should be adjusted according to the purpose of the analysis before the analysis operation. Traditionally, this adjustment has relied on the knowledge and experience of the person conducting the analysis, but the adjustment items include sensitivity, resolution, mass calibration, etc., and of course sensitivity and resolution are related, as well as changes in resolution. Since the center position of the mass peak shifts, mass calibration is required, and since sensitivity, resolution, and the center of the mass peak move in relation to each other, the adjustment operation was a very complicated and arduous task. .

C. Purpose The present invention aims to reduce the burden on analysts when adjusting a quadrupole mass spectrometer.

D. Configuration The device of the present invention measures in advance the movement of the center of the mass peak when the resolution is changed using a quadrupole mass spectrometer, and based on this measurement data, automatically changes the mass according to the resolution setting. This is a correction.

The reason why the center of the mass peak moves when the resolution is changed in a quadrupole mass spectrometer will be explained with reference to FIG. A quadrupole mass spectrometer has four electrodes that are facing each other and have the same polarity, while adjacent electrodes have opposite polarity.
A high frequency alternating current voltage is applied. 1st
The figure is called a stability diagram, where the horizontal axis represents AC amplitude V and the vertical axis represents DC voltage U. The triangular curve shows that voltages U and V for an ion with mass M are inside this triangular curve. At some point, the ion's trajectory is stable and it can pass through the quadrupole space and enter the ion detector, but when U and V are set outside the triangular curve, the ion's trajectory is unstable and diverges. As a result, ions cannot enter the detector. If the mass is different, this triangular curve will be different, and the triangular curve for lighter ions will be smaller and move further to the left. Therefore, if U and V are changed by a program that changes the values of U and V along the straight line P, an ion with mass M will change U1 and V from U1 and V1 to U1 + ΔU as shown in Figure 1. , V1+ΔV is detected by the ion detector. Therefore, if the ion detection output is recorded using the amplitude V of the AC voltage as a parameter representing the mass, a mass spectrum profile as shown in FIG. 2A can be obtained. If the value of V at the center of the peak width in this case is Vp, then U,
When the change program of V is set as a straight line P, the display device is adjusted so that Vp indicates the mass M. Similarly, if the program of changes in U and V is set as the straight line Q in Figure 1, an ion of mass M is detected while the AC amplitude V changes from V1' to V1' + ΔV', and in this case The profile of the mass spectrum becomes as shown in Figure 2B, and the peak width becomes wider, and since the stability diagram is asymmetric, the peak center moves from Vp to Vq. On the other hand, as the peak width becomes wider, the sensitivity improves and the resolution decreases.

The shape of the stability diagram for an ion with mass M changes depending on the dimensions of the quadrupole, the arrangement spacing, etc. Therefore, when the resolution is changed, the relationship between the amount of movement of the center position of the mass spectrum and the resolution is unique to each device. becomes a function of In the present invention, this function form is investigated in advance, and in the case of actual equipment adjustment, the amount of movement of the center of the mass peak with respect to the arbitrarily set resolution is determined from the function form, and the mass scale is automatically adjusted. It is calibrated to

E. Embodiment FIG. 3 shows an embodiment of the present invention. Q is a quadrupole mass spectrometer, and E is a quadrupole power source that generates the DC voltage U and high frequency AC V as described above. C is
It is a CPU and sends a control signal to the quadrupole power supply E.
While changing V, the amplitude V of the high frequency AC voltage
The data is multiplied by a coefficient K, the mass M is calculated from the value of V by M=KV, and the value of M is displayed on the display device D. Here, as mentioned above, the value of K changes depending on the resolution setting, so the data of the relationship K = (R) between the resolution R and K is stored in advance in the CPU by actual measurement, and the value of K is changed according to the resolution setting. It is sufficient to immediately display the mass as M=(R)・V according to the setting of The value of U/V is adopted as the data of M=g
The mass is displayed on the display device D as (U/V)·V.

The actual form of g(U/V) is obtained by setting three types of U/V values using ions of known mass M, and in each case, the value of V at the center of the mass spectrum peak, V1,
Measure V2 and V3, and from the measured values of these three points, g (U/V) = A (U/V) ² + B (U/V) + C
……(1) Assuming that g(U/V) is given in the form, the coefficient A,
Calculate B and C and store them in the CPU memory. To calculate the above coefficient, when U and V are set to U1 and V1, g(U1/V1)=M/V1=A(U1/V1) ² +B(U1/V1)+C...(2) (2 ) can be used for V2 and V3, so A, B, and C can be found from these three equations.

FIG. 4 shows a flowchart of the analysis operation. When the analyst sets the resolution arbitrarily (U/V settings) and presses the calibration key, the CPU reads A,
Read the data of B and C, calculate g (U/V) by substituting the set value of (U/V) according to the above formula (1), and store the result in memory. Once started, the value of g(U/V) memorized in step 2 is used from now on, and the mass number is displayed on the display by multiplying the current value of V by g(U/V). To perform the display.

In the above example, g(U/V) was expressed as a quadratic equation, but it may also be expressed as a broken line.

F. Effect According to the present invention, the calculation data that relates the value of K and the resolution, such as A, B, and C in the above example, where mass M = KV, are obtained by actual measurements on the manufacturer's side and stored in the memory of the control CPU. If the user selects an appropriate balance between resolution and sensitivity according to the analysis purpose, the mass calibration for the quadrupole power source (U or V) will be completed automatically. This greatly reduces the burden on analysts in adjusting the equipment, reduces the time spent on adjustments, and improves analytical efficiency.
The reliability of analysis results is improved because no errors are introduced into the adjustments.

[Brief explanation of the drawing]

Figure 1 is a stability diagram of a quadrupole mass spectrometer, Figure 2 is a graph showing how the peak center shifts depending on resolution, Figure 3 is a block diagram of the device of the present invention, and Figure 4 is a graph showing how the peak center shifts depending on the resolution.
The figure is a flowchart of the operation. Q...Quadrupole mass spectrometer, E...Quadrupole power supply,
C...CPU, D...Display device.

Claims (1)

[Claims] 1. If data specifying the relationship between the coefficients that relate mass and quadrupole voltage and resolution are stored in memory in advance, and the resolution is set during the adjustment operation,
A program that uses the data stored in the memory to calculate coefficients according to the set resolution;
A quadrupole mass spectrometer comprising a control circuit having a program for calculating and displaying a mass corresponding to a quadrupole voltage using the calculated coefficient.