Interfering Reactions

The sensitivity of NRA is affected by reaction cross sections, interfering reactions and other background effects. Flence, it is impossible to make general statements as... 

The potential of the working electrode is thus stabilised by the reagent-generating reaction, and hence is prevented from drifting to a value such that an interfering reaction may result. 

Fig. 2. Current-potential curves in Evans diagram [29] format for reduction of Cu2+ ions and oxidation of H2CO. and are the equilibrium, or open circuit, potentials for the Cu2+ reduction and H2CO oxidation reactions, respectively. Assuming negligible interfering reactions, the vertical dashed lines indicate the exchange current densities for the two half reactions, and the deposition current for the complete electroless solution. Adapted from ref. 23.

Such equilibrium constants enable calculations and deductions to be made for real systems and may be used to assess the progress of a particular reaction amongst a number of competing or interfering reactions. From this consideration the possibility of masking interfering reactions also emerges. Suppose the solution above contains a second metal ion N + which can also react with L . If the amount of L is limited, N + will be in competition with M +. Its effect, however, may be masked if A can be selected to react... 

If y/D/k F> A the reaction takes place in the bulk of the solution. When these conditions hold for all interfering reactions, the system may be analyzed according to the usual procedures of homogeneous kinetics as far as time responses and product distribution are concerned. The sole role of the electrode reaction is then to deliver the intermediate B in the bulk of the solution at a rate defined by... 

Electroless Deposition in the Presence of Interfering Reactions. According to the mixed-potential theory, the total current density, is a result of simple addition of current densities of the two partial reactions, 4 and However, in the presence of interfering (or side) reactions, 4 and/or may be composed of two or more components themselves, and verification of the mixed-potential theory in this case would involve superposition of current-potential curves for the electroless process investigated with those of the interfering reactions in order to correctly interpret the total i-E curve. Two important examples are discussed here. 

The second example is electroless deposition of copper from solutions containing dissolved oxygen (49,53). In this case the interfering reaction is the reduction of the oxygen, and the cathodic partial current density is the sum of two components ... 

Conclusions. The discussion in this section shows the validity of the mixed-potential theory for electroless deposition of Cu, Ni, and An. The discussions in the sections Electroless Deposition in the Presence of Interfering Reactions and Interaction Between Partial Reactions illustrate the complexities of electroless processes and the presence of a variety of factors that should be taken into account when applying the mixed-potential theory to the electroless processes. 

Interpenetrating polymer networks are defined in their broadest sense as an intimate mixture of two or more pol)Mners in network form [1,2]. Ideally, they can be synthesized by either swelling the first crosslinked polymer with the second monomer and crosslinker, followed by in-situ polymerization of the second component (sequential IPN s) or by reacting a pair of monomers and crosslinkers at the same time through different, non-interfering reaction mechanisms, simultaneous interpenetrating networks, SIN s. In fact, many variations of these ideas exist in both the scientific and the patent literature. In any case, at least one of the two components must have a network structure, as an IPN prerequisite. ... 

Four basic requirements for accurate and precise determination of the amount of fluoride or total fluorine in any type of the sample are (1) the sample has to be appropriately pre-treated so that the required form of fluorine can be determined (2) interfering reactions have to be effectively suppressed (3) the final concentration of fluorine must be above the detection limit of the method and (4) if possible, method should be validated using certified reference material (CRM), or the results of analyses compared to the results obtained by an independent method. 

HCI CR- 2CuC CR + 2HC1. The liberated HCl is titrated with std alkali. This method is not as accurate as silver methods, but it is applicable to samples with which silver cannot be used because of interfering reactions... 

Table II summarizes the parameters which relate to the measurement of each element neutron activation products, half-lives, y-ray energies, lengths of irradiation, decay, and counting. Also listed are the possible interfering radionuclides and interfering reactions producing the same isotopes from another element which were necessarily evaluated. This table is subdivided into three sections representing the elements determined during each of the three counting intervals.

The interfering reactions were evaluated by irradiation of pure element standards with corrections applied where necessary. The only... 

Similar to conjugated (interfering) reactions, parallel reactions must be synchronous, which is their obvious fundamental property. 

Meanwhile, consecutive reactions may never be synchronous. This is the principal difference between these two systems—synchronous and usual reactions. As a matter of fact, the final product of the first stage of consecutive reactions is the initial compound for the second stage, therefore, these stages may never be simultaneous (synchronous). Thus, the main difference between synchronous parallel and conjugated (interfering) reactions is that the first type eliminates even a possibility of interaction, whereas in the second case they may only be interacting reactions. 

If/A2 > /Ai, three alternatives of the chemical system with interrelated (interfering) reactions may be realized ... 

Nevertheless, equation (2.17) may help in determining the determinant and detecting the type of interrelated reactions from it. It should be noted here that, in the broad sense of the word, interrelated (interfering) reactions are only those proceeding via general intermediate substances, capable reagents, initiators or catalysts of secondary reactions. Otherwise, this class of reaction may be added to by consecutive reactions, which are not coherent. 

Figure 2.2 Theoretical kinetic curves for interfering reactions (primary 1 and secondary 2) of extreme (a) and asymptotic (b) type A is the phase shift.

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