Transition elements, trace

Selective extraction experiments were then performed to see transference of some transition elements (Cu ", Ni ", Co ", and Fe " ) from the aqueous phase to the organic phase by the synthesized polymeric calixarenes. Phase-transfer studies in water-chloroform confirmed that polymer 2b and 3b were Fe ion-selective as was its monomer (1). Extraction of Fe " cation with 2b and 3b was observed to be maximum at pH 5.4. Only trace amounts of other metal cations such as Cu, Ni ", and Co " were transferred from the aqueous to the organic phase (Table 3). Furthermore, the extracted quantities of these cations remained unaffected with increasing pH. The effect of pH on the extraction of 3b was lower and 56% extraction was accomplished even at pH 2.2. The extraction experiments were also performed with calix[4]arene (1) the ratio was 8.4% at pH 2.2. The polymeric calix[4]arenes were selective to extract Fe " from an aqueous solution, which contained Cu +, Ni, Co ", and Fe " cations, and it was observed that the... 

Riccardo et al. [841] showed that chitosan is promising as a chromatographic column for collecting traces of transition elements from salt solution and seawater, and for recovery of trace metal ions for analytical purposes. Traces of transition elements can be separated from sodium and magnesium, which are not retained by the chitosan. 

Concerning minor and trace elements, in joesmithite Be " is found in site T. Moreover, Ge-amphiboles have been synthesized in which Ge" " completely replaces in sites Tl and T2 (Grebenshchikov et al., 1974). Transition elements Co, Ni, and Cr " appear to occupy sites Ml, M2, M3, and M4, whereas Zn is stabilized essentially in sites Ml, M2, and M3 (Klein and Ito, 1968). 

The UVV spectrum of 32a is pH dependent In the presence of Li+ ions the spectrum of 32b shows a specific shift that allows quantation, which is carried out at 490 nm, pH 13. Possible interference by traces of heavy and transition elements is masked witii [Mg-EDTA] added to the sample. The metiiod was tested for Li" " in seawater and deproteinized plasma. f Determinations of Li in drugs and blood serum are carried out at 601 nm in alkaline solution. Originally designed for colorimetric determination of thorium in trace amounts. Measurements of tile hthium complex can be carried out over a wide range of wavelengths Determination in pharmaceuticals at 468 nm, with linear range of 0.1 to 4.0 mg analysis of blood serum at... 

If vitamins are added to a product to make a nutritional claim, it is critical that shelf-life studies are undertaken to prove that the overages added are sufficient to ensure that the label claims can be met at the end of product shelf life. This is important as none of the vitamins are fully stable in a soft drink environment and some, for instance vitamin C, are very quickly lost in the presence of oxygen. The addition of the fat-soluble vitamins to a soft drink also offers a formulation challenge to ensure that they are fully dispersed and that there are no problems with neck ringing during storage. Trace metals, particularly the transition elements, can also have a deleterious effect on vitamin shelf life, and sometimes metal scavengers, such as EDTA or phosphate salts, are added to improve the shelf life. 

The metal ions of major biological significance are indicated in Figure 1, which shows part of the Periodic Table. Some information on the distribution and concentration levels of these metals in living systems is shown in Table 1. The transition metals and zinc are usually regarded as trace elements, as they are present in very small amounts. Of the transition elements, iron is the most abundant metal, and probably the most well studied. Iron is essential for all living systems with the exception of certain members of the lactic acid bacteria, which grow in environments notoriously low in iron, such as milk. Lactic acid bacteria are devoid of cytochromes, peroxidases... 

XRF offers a unique approach for rapid, non-destructive elemental analysis of liquids, powders, and solids. Although the first row transition elements are the most sensitive, elements from atomic number 12 (magnesium) and greater can be measured over a dynamic range from trace (ppm) to major (percent) element concentrations. EDXRF is well suited for qualitative elemental identification of unique samples, while WDXRF excels at high precision quantitative analysis. 

Segar DA, Gilio JL. 1973. The determination of trace transition elements in biological tissues using flameless atom reservoir atomic absorption. Int J Environ Anal Chem 2 291-301. 

Cadmium is located at the end of the second row of transition elements. The +2 oxidation state of the element is the only one exhibited in its compounds. In its compounds, cadmium occurs as the Cd2+ ion. Cadmium is directly below zinc in the periodic table and behaves much like zinc. This may account in part for cadmium s toxicity because zinc is an essential trace element, cadmium substituting for zinc could cause metabolic processes to go wrong. 

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