The Quadrupole Mass Filter

The quadrupole mass filter is the most widely employed type of mass analyser in current use. It comprises four metal rods accurately aligned around a central axis. RF and DC voltages on the rods create a complex electrostatic field within the area bound by them. Ions entering this region are acted on by the electrostatic field and their motion through the rods can be likened to two superimposed sine waves. Under these conditions the forces acting on most ions cause the amplitude of the oscillations to increase and accelerate them into the quadrupole rods. However, some ions are not accelerated into the rods and undergo trajectories that traverse the full length of the rods. The parameters that govern the equations of motion of ions in a quadrupole mass filter are the mass to charge ratio of the ions, the spacing between the rods, the frequency of the RF voltage and the magnitude of the RF and DC voltages. Hence the RF and DC voltages may be selected such that ions of only one m/z value have 'stable' trajectories. By varying the RF and DC voltages but keeping the ratio between them the same a range of m/z values can be made to undergo stable trajectories, be brought to focus on the detector and a mass spectrum recorded.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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