Question

In: Chemistry

Explain how a quadrupole works? (MS)

Explain how a quadrupole works? (MS)

Solutions

Expert Solution

This is a simple explanation of a complicated device. A quadrupole is a set of four rods with a space down the middle. The ions enter this space. The rods are electrically connected to eachother in opposite pairs. A constant (DC) voltage and an alternationg (AC) voltage are applied to the two pairs of electrodes.

The aleternating electric field makes the ions go off into spirals as they pass down the quadrupole. The constant voltage drags them in one constant direction, towards one pair of electrodes.

A small ion will be dragged a large distance by the alternating field, and will find itself in stronger and stronger regions of field. It will quickly collide with an electrode and disappear.

A very large ion will not be affected much by the alternating field, but will gradually drift in the constant part of the field (the DC part). The alternating field is not strong enough to drag it back as it wanders, so it also collids with and electrode, and is lost.

An ion that is the right size drifts slightly in the constant part of the field, but is always dragged back by the alternating part. The alternating part, however, is not quite strong enough to make it spiral out of control into an electrode. Thus an ion just the right size is stable in this quadrupole field and reaches the end, where it can be measured.   

The stability of an ion in a quadrupole (its chance of making it through the quadrupole without wandering so far from the "safe" region in the middle that it hits an electrode and is lost) therefore depends on the sizes of the alternating and constant fields. It is possible to draw stability diagrams describing whether an ion is stable or not at any given pair of voltages, AC and DC.


Related Solutions

explain how Sanger sequencing works
explain how Sanger sequencing works
Explain how propeller synchronization system works and also how the Synchrophasing system works. What are the...
Explain how propeller synchronization system works and also how the Synchrophasing system works. What are the benefits?
Explain how a cap-and-trade program works.
Explain how a cap-and-trade program works.
briefly explain how heat engine works
briefly explain how heat engine works
Explain how and why synthetic division works.
Explain how and why synthetic division works.
Explain how the cash flow cycle works.
Explain how the cash flow cycle works.
explain how the financial system works in Oman?
explain how the financial system works in Oman?
Explain how the cash flow cycle works.
Explain how the cash flow cycle works.
Briefly explain how the hype cycle works.
Briefly explain how the hype cycle works.
Explain how lateral inhibition works and how it can explain the simple Provide an overview of...
Explain how lateral inhibition works and how it can explain the simple Provide an overview of the basic organization of the visual system from the eye up to the primary visual cortex. Include the three layers of neurons in the retina, circular receptive fields, the lateral geniculate, ocular dominance columns, and simple + complex cells. effect. Include a discussion of brightness effects that are unlikely to be due to lateral inhibition.
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT