Cobalt, absorption factor

The amount of each element required in daily dietary intake varies with the individual bioavailabihty of the mineral nutrient. BioavailabiUty depends both on body need as deterrnined by absorption and excretion patterns of the element and by general solubiUty, and on the absence of substances that may cause formation of iasoluble products, eg, calcium phosphate, Ca2(P0 2- some cases, additional requirements exist either for transport of substances or for uptake or binding. For example, calcium-binding proteias are iavolved ia calcium transport an intrinsic factor is needed for vitamin cobalt,... 

The liquid-phase oxidation of acrolein (AL), the reaction products, their routes of formation, reaction in the absence or presence of catalysts such as acetylacetonates (acac) and naphthenates (nap) of transition metals and the influence of reaction factors were discussed in an earlier paper (22). The coordinating state of cobalt acetylacetonate in the earlier stage of the reaction depends on the method of addition to the reaction system (25, 26). The catalyst, Co(acac)2-H20-acrolein, which was synthesized by mixing a solution of Co(acac)2 in benzene with a saturated aqueous solution, decreases the induction period of oxygen uptake and increases the rate of oxygen absorption. The acrolein of the catalyst coordinated with its cobalt through the lone pair of electrons of the aldehyde oxygen. Therefore, it is believed that the coordination of acrolein with a catalyst is necessary to initiate the oxidation reaction (10). 

Sulfite Oxidation Method The sulfite oxidation method is a classical, but still useful, technique for measuring /cgfl (or [4]. The method is based on the air oxidation of an aqueous solution of sodium sulfite (Na SOg) to sodium sulfate (Na.,SO ) with a cupric ion (Cu " ") or cobaltous ion (Co ) catalyst. With appropriate concentrations of sodium sulfite (about 1 N) or cupric ions (>10 inolH ), the value of k for the rate of oxygen absorption into sulfite solution, which can be determined by chemical analysis, is practically equal to Zr, for the physical oxygen absorption into sulfate solution in other words, the enhancement factor E, as defined by Equation 6.20, is essentially equal to unity. 

Schilling s test assesses the oral absorption of vitamin B12 and is used to diagnose pernicious anaemia. The patient is injected intramuscularly with non-labelled vitamin B12, to saturate body stores. An oral dose of vitamin B12 labelled with cobalt-58 is administered, followed by a second dose labelled with cobalt-57 bound to intrinsic factor. Prior saturation of body stores ensures any absorbed radiolabelled vitamin B12 is rapidly excreted in the urine. Urinary excretion of orally administered vitamin B12 is low in patients with pernicious anaemia due to poor absorption. Absorption is increased when it is administered with intrinsic factor. The ratio of cobalt-57 to cobalt-58 is thus raised in patients with pernicious anaemia. Intrinsic factor antibody testing is now generally used to diagnose pernicious anaemia, though the Schilling s test may occasionally be used. 

Tris(pyrrolidine dithiocarbamato-)—cobalt(III) chelate, the precipitate formed by adding ammonium pyrrolidine dithiocarbamate to cobalt(II) solutions, has been found to be a good matrix for preconcentrating lead and several other metals by co-precipitation. Concentration factors of 40 to 400 are available by the method. The analyte is co-precipitated on the Co-APDC from a litre of sample. The precipitate is filtered on a fine porosity glass sinter and redissolved in a small volume of 6 M nitric acid. The solution is then used for atomic absorption analysis. 

As the name suggests, cyanocobalamin (vitamin B12) is a compound of cobalt (Co(lll)). With a complex organic structure, this essential water-soluble vitamin is obtained from dietary animal sources and is required for deoxyribonucleic acid (DNA) synthesis, where enzymes that use vitamin B12 are involved in the transfer of one-carbon units. The absorption of this vitamin from the gastrointestinal tract only occurs when intrinsic factor glycoprotein is present. While the body can store up to a 12-month supply of vitamin B12, rapid growth or conditions causing rapid cell turnover can increase the body s requirement for this vitamin. 

Similar demands for speciation of trace elements exist for food analysis. Substantial differences in the biological availability are known for several essential elements and depend on the form in which they are present in the diet. The chemical bases for these differences are known for cobalt, iron, and chromium but not for zinc, copper, and selenium. The importance of speciation in food analysis is best demonstrated by the example of iron. That element, when part of heme compounds, is well absorbed, and there is little influence on the absorption by other factors in the diet. Nonheme iron, on the other hand, is not readily absorbed and, in addition, is subject to many influences from dietary ingredients those influences are poorly understood and probably not completely known (14). 

One method used to isolate a X-ray line from unwanted background and noise, employs equilibrated filters. It consists of linking the concentration of interest to the difference between two measurements. The first is obtained by installing a transmission filter between the sample and the detector to isolate the characteristic radiation of the element wanted and the second by fitting an absorption filter which is opaque to this same radiation. This will enable, for example, to quantify the copper from its main spectral line by using two filters, one made of nickel and the other made of cobalt. The fluorescence originating from the filters themselves is a limiting factor in this method, which is reserved for routine measurements. 

The chemical method used to estimate the interfacial area is based on the theory of the enhancement factor for gas absorption accompanied with a chemical reaction. It is clear from Equations 6.22 to 6.24 that, in the range where y> 5, the gas absorption rate per unit area of gas-liquid interface becomes independent of the liquid phase mass transfer coefficient kL, and is given by Equation 6.24. Such criteria can be met in the case of absorption with an approximately pseudo first-order reaction with respect to the concentration of the absorbed gas component. Reactions that could be used for the chemical method include, for example, C02 absorption in aqueous NaOH solution, and the air oxidation of Na2S03 solution with a cupric ion or cobaltous ion catalyst (this is described in the following section). 

The absorption of ingested inorganic cobalt occurs to about 25% (5-45%) depending on the chemical form and nutritional factors such as the content of iron, amino acids, and proteins [5,14-17]. The absorption takes place in two steps, like that of iron, with which Co shares the absorptive pathways in the duodenal mucosa and the proximate small intestine. The two metals mutually compete, each inhibiting the absorption of the other [5,14,18-20]. 

Cyanocobalamin is widely distributed in living organisms it is found in bacteria, in algae and in animal tissues, but it does not appear to be present in the green leaves of plants. For man, it is an important vitamin, being one of the extrinsic factors of haemopoiesis. It was crystallized in 1948 the crystals are dark red, melt at 320 and their solution has well pronounced absorption bands at 278, 361 and 550 m/i. It contains cobalt and phosphorous and the molecular weight is around 1,500. On acid hydrolysis, cyanocobalamin yields 5,6-dimethylbenzimidazole, ribofuranose, phosphoric add, l-amino-2-propanol and a cobalt complex in which the metal... 

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