Aluminum , biology review

This group of aluminum carboxylates is characterized mainly by its abiUty to gel vegetable oils and hydrocarbons. Again, monocarboxylate, dicarboxylate, and tricarboxylate salts are important. The chemical, physical, and biological properties of the various types of aluminum stearates have been reviewed (29). Other products include aluminum palmitate and aluminum 2-ethylhexanoate (30). 

Reliable evaluation of the potential for human exposure to aluminum depends in part on the reliability of supporting analytical data from environmental samples and biological specimens. In reviewing data on aluminum levels monitored or estimated in the environment, it should also be noted that the amount of chemical identified analytically is not necessarily equivalent to the amount that is bioavailable. The analytical methods available for monitoring aluminum in various environmental media are detailed in Chapter 6. 

It is worth mentioning that certified reference data were not available for the elements aluminum, titanium, vanadium, boron, nickel, and phosphorus at the time of analysis. This is a frequent problem in multielement analyses. It is diflBcult to obtain standard biological reference materials similar to the samples being analyzed with more than but a few certified analytical results. The lack of standard reference material limits quality assurance review of the data and diagnosis of analytical problems. The recent issue of new standards such as spinach leaves and brewers yeast will improve the material variety. Certification of more elements in the existing standards will also greatly assist the analyst. 

We have chosen to discuss a large area of bioinorganic chemistry and, clearly, we cannot be comprehensive. Therefore we have concentrated on selected topics, and have provided a detailed list of review articles that cover related areas that we do not address. Even so, there are relevant questions few authors have tackled. For example, aluminum is almost as abundant as iron in the sea yet is almost totally excluded from biological organisms, while iron is particularly sought after. What is the nature of the selection process that discriminates against aluminum ... 

The key to the success in aluminum monitoring lies in the availability of accurate and precise analytical methods together with guidelines for contamination-free specimen collection and the performance of quality assurance. Savory and Wills [19,20], Oster and Prellwitz [21], and Taylor and Walker [22] reviewed the analytical methods for the determination of aluminum in biological materials and the problems associated with aluminum measurements, and provided reconunenda-tions for the preanalytical phase and control of contamination. 

Several methods are available for the determination of total aluminum in biological and other materials. Chemical and physicochemical methods are in most practical situations insensitive and inaccurate X-ray fluorescence is specific but lacks sensitivity neutron activation analysis is complex and subject to interferences, although it is a very sensitive technique. Nuclear magnetic resonance spectroscopy is not very sensitive but useful to get information on speciation [33]. Graphite furnace atomic absorption spectrometry (GFAAS) is the most widely used technique and can produce reliable results, provided that the matrix effects are recognized and corrected. Savory and Wills [19] reviewed chemical and physicochemical methods for the determination of aluminum in biological materials, e.g. X-ray fluorescence, neutron activation analysis, atomic emission spectrometry, flame emission, inductively coupled plasma emission spectroscopy, and AAS. 

Several authors have proposed graphite furnace AAS (GFAAS) methods for the determination of aluminum in biological materials [28,32,34-36]. These methods have improved considerably the aluminum determination in biological body fluids they were critically reviewed by Savory and Wills [19] and Taylor and Walker [22]. In the authors laboratories the following detailed working procedures are used for the determination of aluminum in plasma/serum or urine [37]. 

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