Cold plasma condition

Bryant CJ, McCulloch MT, Bennett VC (2003a) Impact of matrix effects on the accurate measurement of Li isotope ratios by inductively coupled plasma mass spectrometry (MC-ICP-MS) under cold plasma conditions. J Anal At Spectrom 18 734-737... 

Grafting of Rayon Fabrics in Cold Plasma Conditions... 

The compounds obtained were extracted 48 hours at room temperature with various solvents (acetone, methanol, water) in order to remove the unreacted polymers and the side-products resulting from grafting agents in cold plasma conditions. 

In the same time, we have found that the phosphorus and nitrogen contents of the grafts (soluble fraction III) are similar to those of the grafting agents, a fact which proves the occurrance of polymer to polymer grafting reactions in cold plasma conditions. 

In our previous works (1 -3) the possibility of the generation of macro- and polyradicals on the cellulosic support, under the cold plasma conditions, by the dehydrogenation of OH groups or the cleavage of 1,5 glucoside linkages was evidenced. 

It can be presumed that under cold plasma conditions, the nitrogen and phosphorus containing polymers can lead also to the macroradicals through dehydrogenation of CH aromatic and aliphatic or NH groups. 

Figure 15 ICP-MS background spectra (plotted on a logarithmic scale) for a sample containing 0.1% nitric acid (a) Conventional plasma conditions (1000 W, 0.77 L/min nebulizer gas flow rate). The Ar+ and 0+ signals are saturating the detector, so their signals are greater than 2 x 109 counts/sec. (b) Cold plasma conditions (600 W, 1.08 L/min nebulizer gas flow rate). Note that full scale in (a) is 10l° whereas in (b) it is 108. (From Ref. 147.)...

Reaction cells appear to be a much better way to reduce signals due to Ar-containing molecular ions and Ar+ itself than the use of cold plasma conditions. Because normal plasma conditions are used, elements with high ionization energies, such as Se and As, do not suffer from sensitivity losses, unlike cold plasma conditions. The severe chemical matrix effects that are typical of cold plasma conditions are prevented. The first commercial ICP-MS instrument to use this concept was introduced by Micromass UK Ltd. However, as noted, reaction product ions must be controlled or removed to prevent other (new) spectral overlaps. 

Plasma conditions and wall materials must also enable a sufficient lifetime of the first wall components for economic reasons. Chemical erosion of graphite leads to significant erosion yields even under low-temperature, cold plasma conditions and can seriously limit the lifetime. Since the tokamak is a fairly closed system, most of the eroded material will be re-deposited somewhere inside the machine. The question of tritium retention and overall inventory in the device is closely connected to the chemical erosion and to possible co-deposition as well [6,7]. In order to minimize the net-erosion and optimize the lifetime of wall components, the re-deposition should be concentrated in areas of major erosion. Another way to minimize chemical erosion is the use of mixed materials, which - in laboratory experiments - display a reduced erosion yield in comparison to pure graphite. 

Denotes that the ICP-MS detection limit was measured under cold plasma conditions. 

Activation of surfaces to create radicals under cold plasma conditions, C-C, C-O, and C-H bonds break and the resulting free radicals appear in a surface layer about 10 nm thick. These unstable radicals may react through a radical mechanism with a monomer such as NVP unless, after the plasma treatment, the substrate is immediately dipped into the monomer solution under inert atmosphere. 

Denotes detection Umits obtained under cold plasma conditions. [Data courtesy of PerkinElmer Inc., Shelton, CT (www.perkinehner.com).]... 

In another study by Sdrobis et al. [57], the effect of modification on cellulose pulp fibers in LDPE was reported. They used unbleached and bleached kraft cellulose pulp fibers modified with oleic acid in cold plasma conditions as reinforcements. The melt-mixed composites contain up to 10 wt% of untreated and modified cellulose pulp fibers with LDPE. They reported that interfacial adhesion between cellulose and matrix could be improved through modification and most of the properties have been improved when the modified pulp fibers were incorporated into composite matrix. Variation of complex viscosity function of angular frequency for composites is shown in Fig. 11.11. 

When operating in this cold plasma mode, the dominant species in the background spectrum are NO", 02", and HjO, replacing the normally observed Ar species. The magnitude of the °Ar 0 molecular species at m/z 56 can also be reduced to levels suitable for the determination of Fe. For example, if the ion current at m/z 56 under normal operating conditions is about 10 Hz, it is typically reduced to about 20 Hz under cold plasma conditions. 

The characteristics of the ICP can be dramatically altered by using a shielding electrode between the RF coil and the plasma. Such shield torches have been used along with lowered RF power, (so-called cold plasma conditions), to achieve dramatic reductions in molecular and atomic ion interferences without comparable reductions in analyte ion response. A significant drawback to the use of cold plasma conditions for ultratrace detection of selected analytes is that more than one ICP operating mode (RF power, aerosol flow rate) is t3q)ically used to analyze the full range of elements of interest. 

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