An ion-to-photon detector (IPD) is a component used for detecting ions in mass spectrometry.

Operation

In an ion-to-photon detector, a photomultiplier tube is coated with a layer of scintillator compound, such as

Rhodamine B Rhodamine B is a chemical compound and a dye. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with fluorometers. ...

or CsI. When the ions pass through the

mass analyzer Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...

of the spectrometer, they strike the scintillator compound and cause the release of photons. These photons are then detected by the photomultiplier tube. A conversion dynode, such as a microchannel plate can also be used between the ion beam and the scintillator to increase the signal. An MCP, when struck by an ion, will release electrons which then strike the scintillator.

Applications

The primary application for ion-to-photon detectors is acting as the detector in

MALDI In mass spectrometry, matrix-assisted laser desorption/ionization (MALDI) is an ionization technique that uses a laser energy absorbing matrix to create ions from large molecules with minimal fragmentation. It has been applied to the analysis of b ...

mass spectrometry. They could, in theory, be used for other types of mass spectrometry as well.

Comparison to other detectors

The conversion efficiency of ions to photons by an IPD is as good as, or better than, the conversion efficiency of ions to electrons by a multichannel plate detector. Ion-to-photon detectors may also detect ions with a mass of up to around 20,000 Da, better than microchannel plates. However, the resolution of the

mass spectrum A mass spectrum is a histogram plot of intensity vs. ''mass-to-charge ratio'' (''m/z'') in a chemical sample, usually acquired using an instrument called a ''mass spectrometer''. Not all mass spectra of a given substance are the same; for example ...

from an IPD equipped spectrometer is slightly lower. The noise in the spectrum, which may come from unfocused, slow speed ions, is also slightly higher.

References

{{Reflist Mass spectrometry