Function and setup of the PlasmaQuant PQ 9000
PlasmaQuant PQ 9000
Edition 05/2014
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5
Function and setup of the PlasmaQuant PQ 9000
5.1
Physical functional principle of ICP-OES
ICP Emission Spectrometry (ICP-OES) makes use of plasma with temperatures of up to 10 000
K. This high temperature is focused on a very small area of approx. 5 cm
3
. The sample is
introduced to this plasma in the form of aerosol (small droplets in a glass). The droplets dry,
melt, vaporize and atomize or ionize. During this process, the analysis channel of the plasma
through which the sample is flowing cools down to approx. 6 000 to 7 000 K.
Atoms and ions are excited to emit light at these high temperatures. The light is broken down by
the device optics into wavelengths ("colors") whose intensity is measured to indicate
concentrations. A detector is used to measure the intensity of the emission line and its spectral
environment. The net intensity of the measured signal is used as a measurand ("peak").
The inert gas argon is used as the operating gas. This gas flows inside a plasma torch made up
of three concentric pipes. The plasma gas (also called cooling gas) flows at a rate of approx. 12
L/min on the outside to cool the external torch pipe. The sample aerosol is injected in the
plasma in the internal pipe, hence its name "injector". The sample aerosol is created shortly
before with a nebulizer and a downstream spray chamber in which larger droplets are
separated.
The exhaust heat of the plasma is dissipated partly by the recirculating chiller and partly by the
exhaust unit.
5.2
Setup of the PlasmaQuant PQ 9000
Essentially the PlasmaQuant PQ 9000 consists of the following components
−
Components for plasma generation (HF generator, induction coil, torch)
−
Sample supply system with hose pump, nebulizer and spray chamber
−
Optical system with transfer optics, spectral photometer and detector
Sampling compartment and plasma compartment
The sample introduction system is freely accessible in the sampling compartment. The torch
and the induction coil, however, are located in the shielded plasma compartment to protect the
user from the high-frequency radiation and the UV radiation from the plasma. The spatial
separation between sample supply and plasma also prevents the heat radiation from the
plasma being transferred without obstruction to the spray chamber and causing a drift there.
