Influencing the resolution and peak shape of the mass spectrometer

Factors that affect the resolution and peak shape of the mass spectrometer include:

1 quadrupole structure and processing and installation accuracy. The increase in the length of the quadrupole L causes ions to experience enough high frequency cycles in the quadrupole field to be sufficiently separated. Therefore, the resolution of the instrument can be improved.

From the full differentiation of the mouth in formula (12-48), the AM/M=2 Aro/ro relation can be obtained. Therefore, high-precision rod processing and assembly can ensure high resolution capabilities.

2 High frequency of high-frequency voltage, increasing the frequency of high frequency cycles in the quadrupole field can increase the resolution.

3 Ion source inlet conditions. Neil-type electron impact ion source is selected to have the smallest ion energy dispersion and high resolution capability can be obtained. The entrance aperture of the ion source should be limited within a certain range to ensure high resolution. In addition, ion source assembly and ion introduction and quadrupole field coaxiality accuracy affect the resolution power and peak shape.

4 Adjust the slope of the mass scan line, ie increase the U/V ratio. From the stable triangle, it can be seen that as the slope of the mass scan line increases, the scan line decreases through the triangle region Δq, so the stable ion with a corresponding mass number of ΔM at Δq also decreases, the resolution power M/ΔM increase. The slope of the scan line is theoretically a/q=0.16784. The resolution power tends to be infinite, but when the actual instrument parameters are adjusted, increasing the slope too much can lead to rapid decrease in sensitivity and peak shape distortion. Therefore, by using the method of adjusting the slope of the quality scan line, the resolution capability can be improved, and the tradeoff can only be selected based on different instruments, and the best parameters can be determined through experiments.

5 Ion introduction energy selection. The low ion introduction energy can increase the number of high-frequency cycles experienced by the ion in the analysis field to achieve the purpose of improving the resolution capability, but at the same time the sensitivity decreases.