Neutron activation analysis metal complexes

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The metal may he analyzed hy atomic absorption or emission spectrophotometry (at trace levels). Other techniques include X-ray diffraction, neutron activation analysis, and various colorimetric methods. Aluminum digested with nitric acid reacts with pyrocatechol violet or Eriochrome cyanide R dye to form a colored complex, the absorbance of which may be measured by a spectrophotometer at 535 nm. 

Techniques can be classified into two main categories those that detect total metal concentrations and those that detect some operationally defined fraction of the total. Methods which detect total concentrations such as inductively coupled plasma spectrometry, neutron activation analysis, atomic absorption spectrometry and atomic emission spectrometry have no inherent speciation capabilities and must be combined with some other separation technique(s) to allow different species to be detected (approach A in Fig. 8.2). Such separation methods normally fractionate a sample on the basis of size, e.g. filtration/ultrafiltration, gel filtration, or a combination of size and charge, e.g. dialysis, ion exchange and solvent extraction (De Vitre et al., 1987 Badey, 1989b Berggren, 1989 1990 Buffle et al., 1992). In all instances the complexes studied must be relatively inert so that their concentrations are not appreciably modified during the fractionation procedure. 

Maintaining the quality of food is a far more complex problem than the quality assurance of non-food products. Analytical methods are an indispensable monitoring tool for controlling levels of substances essential for health and also of toxic substances, including heavy metals. The usual techniques for detecting elements in food are flame atomic absorption spectroscopy (FAAS), graphite furnace atomic absorption spectrometry (GF AAS), hydride generation atomic absorption spectrometry (HG AAS), cold vapour atomic absorption spectrometry (CV AAS), inductively coupled plasma atomic emission spectrometry (ICP AES), inductively coupled plasma mass spectrometry (ICP MS) and neutron activation analysis (NAA). 

Other Metal-Peptide and -Protein Interactions.—The determination of protein-bound trace elements in biological material by neutron activation analysis has been described Zn, Hg, Cu, and Se were accurately detected in human liver samples, provided that most of the element concerned was protein bound. An interaction of mercury with a protein or a protein-DNA complex has been invoked to explain the partitioning of the metal in euchromatin over heterochromatin (from mouse liver nuclei) by a 10 1 ratio. " Bovine retinas, isolated rod outer segments and emul-phogene extracts of rod outer segments have been shown to contain appreciable amounts of Zn ", Ca and the zinc levels being light sensitive. 

Volatile complexes of organic compounds of metals are, however, used more widely in GC analysis [45, 46, 211]. The main adwmti e of the GC analysis of volatile compounds of metals is the possibility of analysing trace amounts of metals with the use of ECDs and microwave emission detectors. When detectors of this type were used, GC methods were compared with such methods as neutron-activation analysis and atomic-absorption spectroscopy. The field of apphcation for this method is indicated in Table 1.5, illustrating the analysis of trace amounts of elements in the form of volatile complexes and compiled from data pubUshed in the literature. 

If ferrous ions are present during assays of DNA and RNA polymerases in which radioactive newly synthesized polynucleotides are precipitated on to filter paper discs in trichloroacetic acid, spuriously high results are obtained, apparently due to acid-insoluble complexes of Fe with substrate nucleotides precipitating on the paper. Clearly ferrous ions should be avoided in assays of this type. The complex Al. ATP is a potent inhibitor of hexokinase, and neutron activation analysis of many commercial samples of ATP has shown that Al is ubiquitous, and the most common metal contaminant It is best removed by passing the ATP preparation over a cellulose polyphosphate column at pH 5. Chelates of ATP with divalent metal ions have been separated from non-chelated ATP using reverse-phase h.p.l.c. ... 

The content of acid-soluble iron in paper is determined by TAPPI standard T434 (iron combined in clay and other complex compounds is presumed to be nonreactive). The presence of iron can be shown by the color produced upon wetting the paper briefly with warm 6N hydrochloric acid and then adding a solution of potassium ferrocyanide or thiocyanate localized specks of iron or rust are indicated by the more intense color formation. Complete analysis of paper for metallic elements has been accomplished by chemical procedures, emission spec-trography, scanning electron microscopy/x-ray, and neutron activation. 

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