Mass Resolution and Peak Width
Overview of Mass Peak
(1)The mass of an ion has no width ina source.
(2)During analysis of the mass,the mass resolution of the instrument gives a width to the mass peak
(3)The mass peak is usually displayed as a centroid-bar in a mass spectrum afterdata processing by the software.
Mass Resolution and Peak Width
A QP-type Mass Analyzer can completely distinguish the two peaks 1u apart from each other.
Overlapping Profile of Two Peaks
The width of peak profile is tuned according to the value set by an operator. In general,a larger width value increases the singnal, but makes a separation of two peaks worse.
How Dose a Mass Peak Define Width
An ion produced in a source has no distribution in mass. However,a peak profile of mass has a width after the mass is separated by the mass analyzer.The left figure shows how this spreading of mass occurs.The blue area is a stability region of mass,which moves to the right hand by scan operation. When a mass enters the region between two dotted lines,an ion having that mass can go through the quadrupole.As long as the mass stays inside this region, the ions will be detected. This is a reason why the peak profile has a width.
Peak Width and Mass Scan Line
When you change a mass scan line by changing the relationship between DC and RF voltages,the peak width is changed. As shown in the figure,if you set tuning parameter to make the slope of the mass scan line small, the speak width of high mass becomes wider than that of low mass. If you translate the scan line upward or downward. the peak width changes at the same rate for the whole mass region.
