Torch design

Many experimental parameters and components affect sensitivity, including the analyte transport efficiency of the sample introduction system and the mean size and size distribution of the aerosol entering the ICP. The plasma torch design, rf generator, load coil, interface between the atmospheric pressure ICP and mass spectrometer, ion optics, mass spectrometer itself, and detector also affect sensitivity. 

Fig. 8-1 Surface-mix and premix torch designs. The illustration of the surface-mix torch is based on the Sharp Flame Hand Torch made by the Bethlehem Apparatus Company, Inc. (Hellertown, PA 18055), reproduced with permission. The illustration of the premix torch is based on the National Torch made by Premier Industries (Fridley, MN 55432), reproduced with permission.

Michaud-Poussel E. and Mermet J. M. (1986) Influence of the generator frequency and the plasma gas inlet area on torch design in ICP-AES, Spectrochim Acta, Part B 41 125—132. 

Major limitations of thermal plasma spray torches are related to the non-uniformity of temperature and velocity distributions, and relatively low deposition rates (about 50 g/min) and deposition efficiencies (50-80%). Various novel plasma torch designs have appeared to... 

Figure 7.33 (a) The components of a liquid sample introduction system for ICP glass concentric nebulizer, demountable three piece quartz torch, torch body, and glass cyclonic spray chamber, (b) The components assembled for use. This torch design is typical of that used in Jobin Yvon ICP instruments. [Courtesy of Glass Expansion Pty, Ltd., Australia (www.GEICP.com).]... 

Since the ICP was introduced by Fassel in the late 1960s, a great deal of research has been performed to optimize the inductively coupled plasma as an emission source (Fassel, 1971 Fassel and Kniseley, 1974 Montaser, 1992 Montaser, 1998). Variations in torch design, gas flows, gas composition, and applied power were just some of the variables that were studied. The end result by the early 1980s was a source that remains essentially unchanged today. The ICP has flow velocities through the torch such that a small amount of injected sample aerosol moves through the plasma in 10 milliseconds. 

The most often used DC torch design, is the one shown in Fig. 40. This type of torch which is used for plasma spraying is available as a general industrial tool for powers up to 100 kW. 

ICP-OES The main consumable supplies in ICP-OES are in the plasma torch and in the sample introduction area. The major consumable is the torch itself, which consists of two concentric quartz tubes and a sample injector either made of quartz or some ceramic material. In addition, a quartz bonnet normally protects the torch from the RF coil. There are many different demountable torch designs available, but they all cost about 600-700 for a complete system. Depending on sample workload and matrices being analyzed, it is normal to go through a torch every 4 months. In addition to the torch, other parts that need to be replaced or at least need to have spares include the nebulizer, spray chamber, and sample capillary and pump tubing. When all these items are added together, the annual cost of consumables for ICP-OES is on the order of 3000-3200. (Note For this exercise, we will not include the cost of a power amplifier [PA] tube, which had a lifetime of approximately 1 year in older-style RF generators.)... 

Each of these torch designs, their typical characteristics and their yplications are described below. 

The plasma torch design offers many advantages such as ... 

Todoli, J. L. and Mermet, J.-M. (2002) New torch design with an in-built chamber for liquid sample analysis by ICP-AES. J. Anal. At. Spectrom., 17, 345-51. 

Gas purity (%) Torch design Mass 35/ counts s" Mass 37/ counts s Isotope ratio... 

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