Radio-frequency plasma torch

The cross-sectional view of an inductively coupled plasma burner in Figure 21-12 shows two turns of a 27- or 41-MHz induction coil wrapped around the upper opening of the quartz apparatus. High-purity Ar gas is fed through the plasma gas inlet. After a spark from a Tesla coil ionizes Ar, free electrons are accelerated by the radio-frequency field. Electrons collide with atoms and transfer their energy to the entire gas. maintaining a temperature of 6 000 to 10 000 K. The quartz torch is protected from overheating by Ar coolant gas. 

The basic set-up and compounds of an ICP-AES and ICP-MS are shown in Fig. 2. The ICP part is almost identical for AES and MS as detection principle. The ICP torch consists of three concentric quartz tubes, from which the outer channel is flushed with the plasma argon at a typical flow rate of 14 1 min-1. This gas flow is both the plasma and the cool gas. The middle channel transports the auxiliary argon gas flow, which is used for the shape and the axial position of the plasma. The inner channel encloses the nebulizer gas stream coming form the nebulizer / spray chamber combination. This gas stream transports the analytes into the plasma. Both the auxiliary and the nebulizer gas flow are typically around 1 1 min-1. The plasma energy is coupled inductively into the argon gas flow via two or three loops of a water-cooled copper coil. A radio frequency of 27.12 or 40.68 MHz at 1-1.5 kW is used as power source. The plasma is... 

There is also a standard test method for determination of major and minor elements in coal ash by inductively coupled plasma (ICP)-atomic emission spectrometry (ASTM D-6349). In the test method, the sample to be analyzed is ashed under standard conditions and ignited to constant weight. The ash is fused with a fluxing agent followed by dissolution of the melt in dilute acid solution. Alternatively, the ash is digested in a mixture of hydrofluoric, nitric, and hydrochloric acids. The solution is analyzed by (ICP)-atomic emission spectrometry for the elements. The basis of the method is the measurement of atomic emissions. Aqueous solutions of the samples are nebulized, and a portion of the aerosol that is produced is transported to the plasma torch, where excitation and emission occurs. Characteristic line emission spectra are produced by a radio-frequency inductively coupled plasma. A grating monochromator system is used to separate the emission lines, and the intensities of the lines are monitored by photomultiplier tube or photodiode array detection. The photocurrents from the detector... 

Inductively Coupled Plasma (ICP) - ASTM D5185 In the ICP method, argon gas is passed through a radio frequency induction coil and heated to a temperature of 8000-10,000 K, producing a plasma. The oil sample, diluted by a low viscosity solvent such as xylene or kerosene, is nebulized and borne by the argon gas carrier into the centre of the plasma torch. The high temperatures excite the metal atoms. 

Figure 4-63. Schematic of kilowatt power level inductively coupled radio-frequency (ICP-RF) plasma torch.

The plasma is energized by a radio-frequency induction coil wrapped around the quartz torch. High-purity argon gas plus analyte aerosol are fed into the torch. After a spark from a Tesla coil ionizes the Ar gas, free electrons accelerated by the radiofrequency field heat the gas to 6 000 to 10 000 K by colliding with atoms. 

Ultrafme refractory carbide and nitride powders can be produced in an inductively coupled radio-frequency (rf) plasma torch.a schematic drawing of a plasma torch for the production of silicon carbide powder is shown in Fig. 14.1. 

Hgure 5.43 A plasma torch for ICR A radio-frequency generator ionizes argon in the tube and accelerates the ions, maintaining heat by sustained collisions. Once the generator is off, the plasma stops forming. 

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