Speciation rate, high

Advantages High analysis rate 3-4 elements per hour Applicable to many more metals than voltammetric methods Superior to voltammetry for mercury and arsenic particularly in ultratrace range Disadvantages Nonspecific absorption Spectral interferences Element losses by molecular distillation before atomisation Limited dynamic range Contamination sensitivity Element specific (or one element per run) Not suitable for speciation studies in seawater Prior separation of sea salts from metals required Suspended particulates need prior digestion About three times as expensive as voltammetric equipment Inferior to voltammetry for cobalt and nickel... 

A key role of the promoter is to moderate the concentration of free iodide. This has a strong influence on catalytic rate, as carbonylation of [MeIr(CO)2l3] is poisoned by iodide. The mechanism in Scheme 3.2 shows how loss of iodide from [MeIr(CO)2l3] is required to generate neutral species which lie on the main pathway for catalytic turnover. Studies on the stoichiometric reaction steps (see Section 3.3.2.1) show that the methyl migration in the neutral tricarbonyl [MeIr(CO)3l2] is greatly favored over the anionic resting state. The mechanism also explains the influence of [H2O] on the Ir speciation. The equilibrium in Eq. (3) means that concentrations of water and F are coupled. Thus, high [HjO] leads to high [I , and... 

Interest in trace element speciation studies in natural waters has increased considerably during the last decade. It has become apparent that data on total concentrations of any element rather than on individual well defined chemical entities, are often inadequate to identify transport mechanisms, ultimate fate and toxicity of particular elements to organisms. A study of the different trace metal species and their relative distribution will assist in understanding the chemical processes that take place in the highly reactive estuarine zone and in the open sea. These processes include the rate at which chemical processes take place, the participation in geochemical processes (precipitation/dissolution, adsorption/desorption). 

Microbore LC offers potential for speciation studies with ICP-MS detection. The lower liquid flow rates associated with the technique cause less mobile phase to reach the plasma. Often the mobile phases used in LC contain organic solvents that cause plasma instability at high flow rates and pressures. Microbore LC is therefore promising for separations using reversed-phase and ion-pairing chromatographic techniques. 

In Chapter 1 the broad statement is made that the rates of metal complexation reactions are generally high. A more refined conclusion can be drawn from Table 2.3, which lists the time scales over which a number of complex formation and dissociation reactions occur that are important in soil solutions and other natural waters.7 Perusal of these data makes clear the point that although they are usually very rapid, complexation reactions do span a time scale ranging over at least 10 orders of magnitude. Thus the kinetics of these reactions can be very important to understanding the aqueous speciation of metals and ligands in detail. 

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