Trace minerals absorption

Trace mineral absorption by young and elderly men is shown in Table II. Zinc absorption was found to be significantly lower in elderly men than in young men who consumed a nearly identical diet. However, no difference in copper or iron absorption was seen between the young and elderly subjects. 

Based on an overview of numerous studies, the extent to which Ca and trace mineral interactions occur appears to be related to such factors as the source of Ca, the ratio of Ca in relation to other minerals, the timing of Ca and trace mineral intake, meal interactions, food formulations, and natural food chemical compositions (Smith, 1988). As described in the following sections, CCM has been evaluated for its impact on the absorption of other minerals and, based on the results of these studies, appears to provide a unique delivery system for dietary Ca that does not appreciably affect the availability or status of other minerals. 

Manganese is an essential nutrient for humans with a daily estimated adequate safe and daily dietary intake of 2.5 to 5.0 mg (1). Yet trace mineral nutriture depends not only upon dietary intake, but also upon availability for absorption. Currently, little is known regarding the influence of dietary factors on the absorption of manganese. Thus the intent of these studies was to (a) develop a test that would readily measure Mn bioavailability in humans and (b) utilize this test to determine the influences of various dietary factors on Mn bioavailability. 

Malabsorption has many causes. Some malabsorptive disorders, for example coeliac sprue, impair the absorption of most nutrients, vitamins and trace minerals (global malabsorption) others, for example pernicious anaemia, are more selective. Pancreatic insufficiency causes malabsorption if >90% of function is lost. Increased lumen acidity (e.g. Zollinger-Ellison syndrome) inhibits lipase and fat digestion. Cirrhosis and cholestasis reduce hepatic bile synthesis or delivery of bile salts to the duodenum, causing malabsorption. Some causes are summarised in Table 4.2. 

Determination of human requirements for dietary trace minerals necessarily includes knowledge of the factors which affect the availability of minerals for absorption Interactions of dietary minerals with organic constituents of the diet and with other minerals are complex Careful study of mineral absorption in human subjects is required to delineate dietary requirements and the factors which affect them ... 

Mineral nutrition influences toxicology in different ways. Interactions concerning the effects of the trace nutrients on detoxication are common. It is recognized that trace mineral elements, such as macronutrients, can influence absorption of xenobiotics. Divalent cations can compete for chelation sites in intestinal contents as well as for binding sites on transport proteins. As is well documented, competitive absorption of Pb and Ca occurs, which is probably due to competition for binding sites on intestinal mucosal proteins mediated by vitamin D. 

Extensive research on the absorption of iron from various types of meals has allowed guidelines to be developed by which the amount of dietary iron available for absorption may be estimated. Iron is the first trace mineral to be thus treated and thus serves as a model for other nutrients (19). The model for estimating bioavailable iron is based on the concept that iron forms a) a pool of heme iron which is readily available to humans and is uneffected by other dietary components and b) a pool of nonheme iron which is of low bioavailability unless enhancing factors are present concommitantly (20). 

The minerals found in United States coals continue to be studied with the availability of improved instrumental procedures such as x-ray diffraction, infrared absorption, and scanning electron microscopy beyond the traditional optical and chemical mineralogical techniques as applied to thin sections, polished pellets, and isolated particles. The minerals may be grouped into the silicates (kaolinite, illite montmorillonite, and chlorite), the oxides (quartz, chalcedony, hematite) the sulfides (pyrite, marcasite, and sphalerite) the sulfates (jarosite, gypsum, barite, and numerous iron sulfate minerals) the carbonates (ankerite, calcite, dolomite, and siderite) and numerous accessory minerals (apatite, phosphorite, zircon, rutile, chlorides, nitrates, and trace minerals). 

Dolomlto Tablets or powdered, made Irom ground dolomitic limestone. Nutritional supplement that provides calcium, magnesium, and other minerals. Rich source ol calcium, magnesium, and other minerals. May also he used as an antacid The consumption ol excessive amounis may reduce the absorption ol certain trace minerals. 

Aluminum—It is not certain whether it is safe to cook such highly acid foods as rhubarb and tomatoes in aluminum pots and pans, because aluminum is dissolved by acid solutions. Abnormally large intakes of aluminum have irritated the digestive tract. Also, unusual conditions have sometimes permitted the absorption of sufficient aluminum from antacids to cause brain damage. Even if the amounts of aluminum leached from aluminum utensils by acid foods are not toxic, there is the possibility that insoluble complexes might be formed between the aluminum and some of the trace minerals, so that the absorption of these nutrients is blocked. 

INTERRELATIONSHIPS. Zinc is involved in many relationships in the metabolism of carbohydrates, fats, proteins, and nucleic acids in interference with the utilization of copper, iron, and other trace minerals, when there are excess dietary levels of zinc in protection against the toxic effects of cadmium, when there is ample dietary zinc in reduced absorption, when there are high dietary levels of calcium, phosphorus, and copper. 

In this work, a method based on the reduction potential of ascorbic acid was developed for the sensitive detennination of trace of this compound. In this method ascorbic acid was added on the Cr(VI) solution to reduced that to Cr(III). Cr(III) produced in solution was quantitatively separated from the remainder of Cr(VI). The conditions were optimized for efficient extraction of Cr(III). The extracted Cr(III) was finally mineralized with nitric acid and sensitively analyzed by electro-thermal atomic absorption spectrometry. The determinations were carried out on a Varian AA-220 atomic absolution equipped with a GTA-110 graphite atomizer. The results obtained by this method were compared with those obtained by the other reported methods and it was cleared that the proposed method is more precise and able to determine the trace of ascorbic acid. Table shows the results obtained from the determination of ascorbic acid in two real samples by the proposed method and the spectrometric method based on reduction of Fe(III). 

Berndt et al. [740] have shown that traces of bismuth, cadmium, copper, cobalt, indium, nickel, lead, thallium, and zinc could be separated from samples of seawater, mineral water, and drinking water by complexation with the ammonium salt of pyrrolidine- 1-dithiocarboxylic acid, followed by filtration through a filter covered with a layer of active carbon. Sample volumes could range from 100 ml to 10 litres. The elements were dissolved in nitric acid and then determined by atomic absorption or inductively coupled plasma optical emission spectrometry. 

For example, the industrial preparation of mineral acids, such as sulfuric, hydrochloric and nitric, inevitably leads to them containing small concentrations of metals as impurities. If the acid is to be used purely as an acid in a simple reaction, the presence of small amounts of metals is probably unimportant. If, however, the acid is to be used to digest a sample for the determination of trace metals by atomic absorption spectrometry, then clearly the presence of metallic impurities in the acid may have a significant effect on the results. For this latter application, high-purity acids that are essentially metal-free are required. 

A convenient method is the spectrometric determination of Li in aqueous solution by atomic absorption spectrometry (AAS), using an acetylene flame—the most common technique for this analyte. The instrument has an emission lamp containing Li, and one of the spectral lines of the emission spectrum is chosen, according to the concentration of the sample, as shown in Table 2. The solution is fed by a nebuhzer into the flame and the absorption caused by the Li atoms in the sample is recorded and converted to a concentration aided by a calibration standard. Possible interference can be expected from alkali metal atoms, for example, airborne trace impurities, that ionize in the flame. These effects are canceled by adding 2000 mg of K per hter of sample matrix. The method covers a wide range of concentrations, from trace analysis at about 20 xg L to brines at about 32 g L as summarized in Table 2. Organic samples have to be mineralized and the inorganic residue dissolved in water. The AAS method for determination of Li in biomedical applications has been reviewed . 

Dietary Reference Intake (DRI) of Cu, 17-18% of the DRI of K, P, and Fe, and between 5 and 13% of the DRI of Zn, Mg, and Mn (Table 5.1). Potatoes are generally not rich in Ca, but can be a valuable source of trace elements, such as Se and I, if fertilized appropriately (Eurola et al., 1989 Poggi et al., 2000 Turakainen et al., 2004 Broadley et al., 2006). Moreover, since potato tubers have relatively high concentrations of organic compounds that stimulate the absorption of mineral micronutrients by humans, such as ascorbate (vitamin C), protein cysteine and various organic and amino acids (USDA, 2006), and low concentrations of compounds that limit their absorption, such as phytate (0.11-0.27% dry matter Frossard et al., 2000 Phillippy et al., 2004) and oxalate (0.03% dry matter Bushway et al., 1984), the bioavailability of mineral elements in potatoes is potentially high. 

Although a number of secondary minerals have been predicted to form in weathered CCB materials, few have been positively identified by physical characterization methods. Secondary phases in CCB materials may be difficult or impossible to characterize due to their low abundance and small particle size. Conventional mineral identification methods such as X-ray diffraction (XRD) analysis fail to identify secondary phases that are less than 1-5% by weight of the CCB or are X-ray amorphous. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), coupled with energy dispersive spectroscopy (EDS), can often identify phases not seen by XRD. Additional analytical methods used to characterize trace secondary phases include infrared (IR) spectroscopy, electron microprobe (EMP) analysis, differential thermal analysis (DTA), and various synchrotron radiation techniques (e.g., micro-XRD, X-ray absorption near-eidge spectroscopy [XANES], X-ray absorption fine-structure [XAFSJ). 

Tncreasing national concern over the ecological and environmental effects of coal combustion coupled with the desire to become more self sufficient in mineral production led the Coal Research Bureau at West Virginia University to examine the major and minor constituents in coal ash. Because of the need for accurate results at the low trace element concentrations, it was felt that atomic absorption spectroscopy could provide a rapid and routine method for analytical determinations. 

Coal contains several elements whose individual concentrations are generally less than 0.01%. These elements are commonly and collectively referred to as trace elements. These elements occur primarily as part of the mineral matter in coal. Hence, there is another standard test method for determination of major and minor elements in coal ash by ICP-atomic emission spectrometry, inductively coupled plasma mass spectrometry, and graphite furnace atomic absorption spectrometry (ASTM D-6357). The test methods pertain to the determination of antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, lead, manganese, molybdenum, nickel, vanadium, and zinc (as well as other trace elements) in coal ash. 

Several other methods have been used to determine the trace elements in the mineral matter of coal, as well as in whole coal and coal-derived materials. These methods include spark-source mass spectrometry, neutron activation analysis, optical emission spectroscopy, and atomic absorption spectroscopy. 

---