__NOTOC__ A trace element, also called minor element, is a

chemical element A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...

whose

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', an ...

(or other measure of amount) is very low (a "trace amount"). They are classified into two groups: essential and non-essential. Essential trace elements are needed for many physiological and biochemical processes in both plants and animals. Not only do trace elements play a role in biological processes but they also serve as catalysts to engage in

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

and reduction mechanisms. The exact definition depends on the field of science: * In

analytical chemistry Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separati ...

, a trace element is one whose average concentration is less than 100

parts per million In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they ...

(ppm) measured in the atomic count or less than 100 micrograms per gram. * In

biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...

, an essential trace element is a

dietary element In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon, ...

that is needed in very minute quantities for the proper growth, development, and physiology of the organism. The dietary elements or essential trace elements are those that are required to perform vital metabolic activities in organisms. Examples of essential trace elements in animals include Fe (hemoglobin), Cu (respiratory pigments), Co (Vitamin B12), Mn and Zn (enzymes). Some examples within the human body are cobalt,

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

, fluorine, iodine, iron, manganese and zinc. Although they are essential, they become toxic at high concentrations. Elements such as Ag, As, Cd, Cr, Hg, Pb, and Sn have no known biological function, with toxic effects even at low concentration. * In

geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the e ...

, a trace element is one whose concentration is less than 1000 ppm or 0.1 % of a

rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...

's composition. The term is used mainly in

igneous petrology Igneous petrology is the study of igneous rocks—those that are formed from magma. As a branch of geology, igneous petrology is closely related to volcanology, tectonophysics, and petrology in general. The modern study of igneous rocks utilizes a ...

. Trace elements will be compatible with either a liquid or solid phase. If compatible with a

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

, it will be incorporated into a solid phase (e.g.,

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

's compatibility with

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...

). If it is incompatible with any existing mineral phase it will remain in the liquid

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

phase. The measurement of this ratio is known as the partition coefficient. Trace elements can be substituted for network-forming ions in mineral structures. Trace elements that are not essential to a mineral's defined composition will not appear in the chemical formula of that mineral.

References

{{Authority control Analytical chemistry Biochemistry Geochemistry Nutrition Physiology

See also

References