Tangential flow torch

A comparison between linear-flow and a tangential-flow torches was made after simplex optimisation of two flow rates, RF power and height above the load... 

The detection of gas phase halogens by He MIP-MS has also been investigated by Brown and co-workers [98]. They utilized a commercially available ICP-MS instrument. The ICP torch box was removed and replaced with an internally tuned TMqio microwave cavity. The He plasma was formed using a demountable tangential flow torch. This was used in an effort to create a central region in the plasma, rich in analyte ions which allows for maximum sensitivity when sampling the plasma with the mass spectrometer. 

Nearly all ICP torches consist of three concentric quartz tubes surrounded by a coil carrying radiofrequency (r.f.) power, referred to as the load coil. The middle tube carries the Ar that forms the plasma while Ar flow in the inner tube serves as a carrier for sample introduction. This punches a hole in the center of the plasma, creating a toroidal plasma with a central axial channel that acts as the atomization-ionization cell. The plasma forms under the load coil, past the exit of the inner and middle tubes. The outer tube extends beyond the coil and carries a tangential flow of Ar that serves as a coolant layer to prevent the torch from melting in addition to centering the plasma. 

Argon gas is supplied at 10-15 1 min" through the three concentric quartz tubes of the torch, shown in Figure 1(a). The tangential flow of gas in the outer tube contains the plasma, while the central tube carries the nebulized sample droplets suspended in argon. 

Figure 2.4 Schematic diagram of an ICP torch. The sample is carried into the torch by the carrier argon gas, and is ignited by radio-frequency heating from the RF coils. The tangential argon flow lifts the flame from the burner, preventing melting. The position of the detector in axial or radial mode is shown. (From Pollard et al., 2007 Fig. 3-3, by permission of Cambridge University Press.)...

Torches One of the torch configurations more commonly used with the ICP is shown in Figure 1. The plasma torch consists of three concentric quartz tubes through which streams of argon flow. The nebulizer gas, which carries the analyte into the plasma, flows in the centre tube. The auxiliary gas flows around the centre tube and adjusts the position of the plasma relative to the torch. The coolant gas streams tangentially through the outer tube, serving to cool the inside walls and centre of the torch, and stabilize the plasma. 

Satzger and co-workers [97] used an atmospheric-pressure He MIP at moderate powers (360 W) with a laboratory constructed plasma MS instrument to detect Br, Cl and I as positive ions. In order to reduce air entrainment in the plasma plume, a torch was designed which provided a tangential sheath flow of nitrogen. The major background ions in the He mass spectrum were found to be N 0 and. To... 

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