Speciation software

In reality, the interaction of chelants with metal ions is determined by a variety of factors pH, temperature, concentration of chelant, and concentration of all metal ions present in the system. The calculations are not simple and are best done by speciation software models, a number of which are available [31]. 

The interaction of natural organics with cations result in various species, but due to the unknown equilibrium constants and the different interactions by various organics involving several mechanisms, the available data is limited. Matlack (1992) modelled the interactions of natural organics with cations in order to determine speciation. He found a general underestimation of the interactions by speciation software due to the assumption of competition between cations. 

Other pattern recognition strategies have been used for bacterial identification and data interpretation from mass spectra. Bright et al. have recently developed a software product called MUSE, capable of rapidly speciating bacteria based on matrix-assisted laser desorption ionization time-of-flight mass spectra.13 MUSE constructs a spectral database of representative microbial samples by using single point vectors to consolidate spectra of similar (not identical) microbial strains. Sample unknowns are then compared to this database and MUSE determines the best matches for identification purposes. In a... 

Table 5.4 Examples of Commercially Available and Free Software for Computing Aqueous Chemical Speciation in Natural Waters.

It does need to be kept in mind, however, that no information on kinetics can be obtained from the software, so that between initial and end (equilibrium) conditions many changes in speciation could be occurring in a system. This is still indicative of... 

Owen et al. [32] used RPLC to speciate Zn compounds in an in vitro gastrointestinal digest of chicken meat. C8 and CJ8 columns were connected in series to achieve the separation. It was found that time resolved acquisition software needed improvement for peak areas to be determined. 

Chemical speciation in soil solutions and other natural waters can be calculated routinely with a number of software products offered in a variety of computational media.27 30 Five examples of these products are listed in Table 2.5. They differ principally in the method of solving the chemical equilibrium problem numerically, or in the chemical species and equilibrium constants considered, or in the model used to estimate single-species activity coefficients. Irrespective of these differences, all the examples follow a similar algorithm ... 

It is inevitable that methodologies not equipped to explore molecular structure will produce ambiguous results in the study of surface speciation. The method of choice for investigating molecular structures is spectroscopy. Surface spectroscopy, both optical and magnetic, is the way to investigate surface species, and thus to verify directly the molecular assumptions in surface speciation models. When the surface species are detected they need not be divined from adsorption data, and the choice of a surface speciation model from the buffet of available software becomes a matter unrelated to goodness-of-fit. 

Components are present in solution in the form of different species. The concentrations of these species depend on the concentrations of all components in the system. Metal cations form aquo complexes and other complexes in which one or more water molecules are replaced by ligands other than water. This problem is discussed in basic handbooks of inorganic and analytical chemistry. Speciation in simple systems can be easily calculated when the stability constants of particular species are available. Specialized software that facilitates calculation of speciation in more complex systems is available. Many errors and misinterpretations related to speciation in solution can be found in the literature. 

Martell, A.E. and Motekaitis, RJ. (1992) Determination and Use of Stability Constants, 2nd edn, John Wiley Sons, Inc., New York, USA. Provides a description of the potentiometric method commonly used to determine stability constants along with how complex speciation is determined, with examples and software. 

MinteqA2 is a geochemical speciation code which was released by the U.S. EPA. Version 3.11 was used in this study. The software is available on the internet from the U.S. EPA Center for Exposure Assessment and Modeling (CEAM) as are several manuals (Allison etal. (1991)). 

Data selections can be exported into a file to be used in other geochemical speciation or reactive transport codes. Then, the output format will automatically be adapted to the specific requirements of the different software packages. 

Nevertheless the combination of a reactive model with an optimization software is easier to obtain with the model approach presented above, than with standard geochemical software, like PHREEQE. By purpose the number of chemical components was kept as small as possible with respect to the regarded processes. By purpose the details of biochemistry, i.e. bacterial speciation (cf. Schafer et al., 1998), were not included. Moreover a high number of relevant (or irrelevant) parameters is surely an obstacle to understand complex (and easy) systems. 

Modern instruments are now being sold with excellent semiquantitative software, light element facilities, and the ability to carry out some speciation. The latter will be dealt with in a separate section below. 

The coupling of chromatography (GC, LC, and ion chromatography (IC)) or capillary electrophoresis (CE) to ICP-MS allows the separation of complex mixtures and speciation by compound or oxidation state of the elements present. GC is described in Chapter 12 LC including HPLC and 1C and the nonchromatographic separation method of CE are described in Chapter 13. All of these separation instruments have been interfaced to ICP-MS systems. Coupling a separation technique to a quadrupole ICP-MS may require the use of additional software that can handle transient signals such software is commercially available, as are complete hyphenated speciation ICP-MS systems. 

A speciation diagram of pure ZnBr2 (primary electrolyte) concentration against solution pH was constructed using OLI Studio software (version 9.2, OLl Systems, Inc.) and is presented in Fig. 5.4. 

The aqueous-speciation and solubility behaviour of U in groundwaters associated with the Tono Uranium Deposit is evaluated in this section using the geochemical constraints discussed above. Supporting calculations were carried out using the Geochemist s Workbench software package [24] and a thermodynamic database described by Arthur et al. [20, 25]. 

Thermodynamic modeling can be extremely useful in understanding the process chemistry and its influence on corrosion and corrosion data, particularly with respect to the speciation of the liquid phase and the potential for solids formation. Software codes for aqueous and nonaqueous systems are available from many sources, but care must be exercised in their use. Special attention should be paid to the source of the thermodynamic data and/or the source of experimental data used to develop the thermodynamic parameters. 

In order to improve our understanding of the speciation of mercuiy in FGD gypsum, the authors have used thermodynamic equilibrium models in order to predict the composition of the chemical species in gas phase using the HSC-Chemistry 5.0 software. The theoretical study was carried out in the same conditions that the experimental study, at atmospheric pressure and temperatures ranging between 25 and 800 C. HSC-Chemistiy program uses data base with enthalpy, entropy and calorific capacity values for more than 15000 species. This software allows modify the quantity of different species implicated in the reaction and the program determines tlie products formed, theoretically, in the equilibrium. 

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