The purge part of the manifold consists of orifices combined with a pressure regulator to control the desired pre-pressure. Nitrogen gas flows, in the range from 0.2 liter per minute to 7 liters per minute, are used to purge the optical section of the ICP-AES, in order to guide away gases that might disturb the emission measurement process.
In the starting years of ICP analysis, the supply of gases was controlled manually. When automation has made its way into this field, also the control of gases was not spared, and mass flow controllers have been introduced. Such a good gas flow control has resulted in an increase in accuracy and stability, and lower detection limits became possible - which is a good point in meeting increasingly stringent environmental requirements.
The manifold is designed for an optimum value/price combination. Cost reduction is a driver in this market, and from the manufacturer's perspective one single supplier for gas related issues is favourable. A compact device has a small footprint, which is important due to the limited space in the lab. The small size of Bronkhorst mass flow controllers is useful here.