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Glossary


EVISA is providing a list of terms used in the area of speciation and fractionation analysis. Since speciation analysis is a field of analytical chemistry that is specified by a pronounced interdisciplinary cooperation between different sciences such as biochemistry, medicine, biology, environmental sciences, nutritional sciences and material sciences its terminology is a complex mixture of terms used in all these.

You may search for a term or browse the glossary alphabetically.

(In case that you cannot find the term you may consult more special glossaries or handbooks about nomenclature. For more details please consult EVISA's List of Glossaries)





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half-life (t 1/2)
The time it takes for half the original amount of a substance to disappear. In the environment, the half-life is the time it takes for half the original amount of a substance to disappear when it is changed to another chemical by bacteria, fungi, sunlight, or other chemical processes. In the human body, the half-life is the time it takes for half the original amount of the substance to disappear, either by being changed to another substance or by leaving the body. In the case of radioactive material, the half life is the amount of time necessary for one half the initial number of radioactive atoms to change or transform into another atom (that is normally not radioactive). After two half lives, 25% of the original number of radioactive atoms remain.
Source: ATSDR  Glossary of Terms

hard ionization
Formation of gas-phase ions accompanied by extensive fragmentation

hazard
Set of inherent properties of a substance, mixture of substances, or a process involving substances that, under production, usage, or disposal conditions, make it capable of causing adverse effects to organisms or the environment, depending on the degree of exposure; in other words, it is a source of danger.

headspace sampling
Gas-phase sampling technique in which solute is removed from an enclosed space above a solid or liquid
sample.

Health Canada
"Health Canada is the federal department responsible for helping the people of Canada maintain and improve their health ."

"In partnership with provincial and territorial governments, Health Canada provides national leadership to develop health policy, enforce health regulations, promote disease prevention and enhance healthy living for all Canadians."

See also the Health Canada Environment page: www.hc-sc.gc.ca/english  (Source: Health Canada website )


heavy ion induced desorption (HIID)
Heavy ion induced desorption (HIID) is the general name for particle bombardment ionization methods using beams of high energy atoms or molecules (20 ~ 300Da) accelerated on the MeV level.

heavy metal
A very imprecise term, never defined by any authoritive body, used loosely to refer to both the element and its compounds. It is based on categorization by density, which is rarely a biologically significant property. It is often used as a group name for metals and metalloids that have been associated with contamination and potential toxicity or ecotoxicity. However, the assumption that all so-called "heavy metals" and their compounds have highly toxic or ecotoxic properties is not supported by facts. Even further, the list of "heavy metals" is not clearly defined and has no basis in their chemistry. Even the term "metal" is commonly misused in both toxicological literature and in legislation to mean the pure metal and all the chemical species in which it may exist.

Very often, ther term "heavy metals" is used, based on one of the following "definitions":

  • In terms of density: Metals having a density greater than 4 (4.5, 5 or 6 g/cm3)
  • In terms of atomic weight: Metals with a atomic weight greater than 23 (40)
  • In terms of atomic number: Metals with an atomic number greater than 20

The use of the term "heavy metals"  is highly discorouged  by IUPAC.


Heme
A near-planar coordination complex obtained from iron and the dianionic form of porphyrin. Derivatives are known with substituents at various positions on the ring named a, b, c, d etc. Heme b, derived from protoporphyrin IX, is the most frequently occurring heme.

hemin
Hemin is an iron containing metalloporphyrin. Specifically, the Fe3+ oxidation product of heme is termed hemin. Hemin acts as a feed-back inhibitor on ALA synthase. Hemin also inhibits transport of ALA synthase from the cytosol (its' site of synthesis) into the mitochondria (its' site of action) as well as represses synthesis of the enzyme. Hemin is also known as a drug that is derived from processed red blood cells. Hemin for injection was known previously as hematin.

hemosiderin
An insoluble iron-protein complex that comprises a storage form of iron mainly in the liver, spleen and bone marrow.

heterocyclic
a cyclic or ring molecular structure in which one or more of the atoms in the ring is an element other than carbon. (Common heterocyclics are pyridine, pyrrole, furan, thiophene, and purine).

heterogeneity
The degree to which a property or a constituent is randomly distributed throughout a quantity of material. The degree of heterogeneity is the determining factor of sampling error.

hexapole
A device containing six rods used as an ion guide to focus divergent beams of ions, as a storage device to accumulate ions before transfer to another part of the system, or as a collision cell. RF voltages are generally applied to the rods. See also octapole

Hg(II) or Hg2+
 - divalent mercury - the dominating mercury form in organic and inorganic mercury compounds. In the atmosphere, mercury species with divalent mercury are more easily washed out of the air with precipitation and deposited than elemental mercury;

Hg(p)
Hg(p) - particulate mercury - mercury bound in, or adsorbed on, particulate material. In the atmosphere, particulate mercury is deposited much faster than elemental mercury;

high-resolution ICP-MS
Also known as magnetic sector, sector field or double focusing ICP-MS. Magnetic sector based ICP-MS instruments are capable of resolution (M/ΔM) of up to 10,000 and are able to resolve most polyatomic species from analytes at the same nominal mass.

homogeneity
Condition of being of uniform structure or composition with respect to one or more specified properties. A reference material is said to be homogeneous with respect to a specified property if the property value, as determined by tests on samples of specified size, is found to lie within the specified uncertainty limits, the samples being taken either from different supply units (bottles, packages, etc.) or from a single supply unit.

humic acid
one of two classes of natural acidic organic polymer that can be extracted from humus found in soil, sediment, or aquatic environments. The process by which humic acid forms in humus is not well understood, but the consensus is that it accumulates gradually as a residue from the metabolism of microorganisms. Humic acid is the humic fraction soluble in alkali, but not in acid. The other organic polymer is fulvic acid.

humic substances
operationally defined fraction of natural organic matter

HYDRAQL
A programme for the computation of chemical equilibrium composition of aqueous batch systems including surface complexation modelling of ion adsorption at the oxide/solution interface.

hydrogen selenide
Hydrogen selenide is a metabolite within the metabolic pathway of selenium.
 
CAS Number : 7783-07-5
Other names: Selenium hydride

hydrolyzable phosphorus
Phosphorus in the sample as measured by the sulfuric acid hydrolysis procedure, and minus pre-determined orthophosphates (EPA, 1979). Includes dissolved and particulate condensed phosphate that is converted to dissolved orthophosphate through acidification of the sample (APHA, 1989). It is referred to as Dissolved hydrolyzable P or Total hydrolyzable P, when measured on filtered or  unfiltered sample, respectively.

hydrophilic
Having an affinity for water; attracting, dissolving in, or absorbing water; readily absorbing moisture; having strongly polar molecular groups that readily interact with water.

hydrophobic
Insoluble in water; the extent of insolubility; not readily absorbing water; resisting or repelling water, wetting, or hydration; or being adversely affected by water.

hydrophobic charge induction chromatography (HCIC)
A type of hydrophobic interaction chromatography (HIC) that is based on pH rather than salt concentration, allowing for elution under relatively mild conditions amd eliminating the requirement for an associated filtration step in early separations.

hydrophobic interaction chromatography (HIC)
A type of liquid chromatography tha makes use of the relative solubility of proteins and matrix materials. Hydrophobic interactions are strongest at high ionic strengths, so salt is usually included to increase those levels.

hydrosphere
Water above, on, or in the Earth’s crust, including oceans, seas, lakes, groundwater, and atmospheric
moisture.

hydroxy-oxide
Hydroxy-oxide is a chemical compound containing oxygen (O), the hydroxyl (OH) anion and some other chemical element. For example, NiOOH is the chemical formula for nickel hydroxy-oxide, and FeOOH that of iron hydroxy-oxide.

hyperaccumulator
The term hyperaccumulator, referring to a plant with a highly abnormal level of metal accumulation, was originally coined to describe a plant with a concentration exceeding 0.1% Ni (dry mass) and then extended to other metals such as Co and Pb (0.1% threshold value) and Zn and Mn (1% threshold value). To date ~400 known metal hyperaccumulators have been reported worldwide. The most widely referred to have been the mustard (Thlaspi caerulescens) containing 1-2% Zn, Alyssum lesbiacum (>1% of Ni), and the New Caledonian tree Sebertia acuminata whose latex was reported to contain above 20% Ni (dry mass).

The discovery of such metal-hyperaccumulating properties in certain plants spurred research towards using them for cleanup of heavy-metal-contaminated soils.


hyphenated technique
The term "hyphenated techniques", introduced by Hirschfeld, refers to an online combination of a chromatographic (later also electrophoretic) separation technique with a sensitive element or molecule specific detector.

see: T. Hirschfeld, Anal. Chem., 52 (1980) 297 A

NB!: A slash is sometimes used instead of hyphen, especially if the name of one of the methods contains a hyphen itself.











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