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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)



abiotic degradation
Process in which a substance is converted to simpler products by physical or chemical mechanisms: examples include hydrolysis and photolysis

abiotic transformation
Process in which a substance in the environment is modified by nonbiological mechanisms.

absolute method
A method of chemical analysis that bases characterization completely on standards defined in terms of physical properties.

Substance that enters and is retained inside a solid or semisolid matrix (absorbent).

A solid that assimilates a gas, liquid, or solute into its interior (compare with adsorbent and sorbent).

The process by which a substance or a xenobiotic is brought into a body (human or animal).
Also: incorporated into the structure of a mineral.

This term is used to describe the relative occurrence of an ion. A mass spectrum is a plot of  the ion abundances against the m/z values determined and is normalised to the most abundant ion. This term should be distinguished from intensity which, while appropriate for the signal of the individual ion peak detected, is not used in spectra.

AC Arc
Plasma created by a power supply or function generator of alternating polarity. Typically, an arc excited at twice the frequency of the electrical grid (50 Hz except North America, which is 60 Hz). While not continuous, the period of low current as the polarity of the driving voltage commutes (switches sign) is brief compared to the overall experiment time.

accelerated solvent extraction (ASE)
Analytical technique of performing static extractions at elevated temperatures and pressures for enhanced extraction efficiency and sample through-put.

accelerating voltage
The accelerating voltage is applied to the source of a mass spectrometer to move ions formed in the source into the mass analyzer of the instrument. This accelerating voltage can be a few tens of volts in quadrupole mass spectrometers to several thousand volts in sector instruments or in time-of-flight mass spectrometers.

The degree of conformity with a standard, or the degree of perfection attained in a measurement. Accuracy relates to the quality of a result, and is distinguished from precision, which relates to the quality of the operation by which the result is obtained.

accurate mass
The accurate mass (or exact  mass) of an ion of specified isotopic composition is calculated  by summation of the exact  masses of the constituent  atoms. Conversely, the empirical formula of an ion can be deduced from the measured accurate mass of the ion if the ion mass is low enough to limit the number of formulaic possibilities and if the exact mass value is known accurately enough. 

A synthetic N-acetyl derivative of the endogenous amino acid L-cysteine, a precursor of the antioxidant enzyme glutathione. Acetylcysteine regenerates liver stores of glutathione. This agent also reduces disulfide bonds in mucoproteins, resulting in liquification of mucus. Some evidence suggests that acetylcysteine may exert an anti-apoptotic effect due to its antioxidant activity, possibly preventing cancer cell development or growth. In addition, acetylcysteine has inhibited viral stimulation by reactive oxygen intermediates, thereby producing antiviral activity in HIV patients

acid digestion
In treating samples, the use of acid to chemically decompose a material into its simpler constituents (usually soluble) thereby releasing the analytes for subsequent analysis.

acid labile mercury
Determined by SnCl2 reduction on acidified samples, includes inorganic complexes, labile organic associations, elemental mercury, and labile particulate mercury. Doesn't measure organic forms (C-Hg bound) of mercury such as methylmercury. Same as reactive mercury.

acid mine drainage
Liquid drainage from bituminous coal mines containing a high concentration of acidic sulfates, especially ferrous sulfate.

acid soluble mercury
Mercury that passes through a 0.45 µm membrane filter after the sample is acidified to pH1-2.0 with nitric acid (EPA 1984). Strongly sorbed Hg is not measured, but all toxic forms as well as some non-toxic forms are measured.

acid volatile sulfides (AVS)
Sulfides in sediments that liberate hydrogen sulfide on reaction with cold dilute acid (mainly FeS or MnS in sediments). AVS is used as a parameter together with SEM (simultaneously extractable metals) to predict toxicity of sediments.
AVS may be chemically available by acid extraction without being bioavailable. Thus, AVS can reduce metal toxicity by binding metals in anoxic soils or sediments, thereby rendering them unavailable to most living organisms.

An element which is any of the second (5f) series of f-block elements or inner transition elements commencing with actinium at atomic number 89 and ending with lawrencium at atomic number 103.

action level
1. Concentration of a substance in air, soil, water or other defined medium at which specified emergency counter-measures, such as the seizure and destruction of contaminated materials, evacuation of the local population or closing down the sources of [pollution], are to be taken.
2. Concentration of a [pollutant] in air, soil, water or other defined medium at which some kind of preventive action (not necessarily of an emergency nature) is to be taken. (IUPAC)

active transport
Movement of a substance across a cell membrane against an electrochemical gradient, in the direction opposite to normal diffusion and requiring the expenditure of energy

in chemistry: The thermodynamically effective concentration of a chemical species or component. In solutions with high ionic strengths, ions interact with each other and are not totally independent chemical units. The interactions affect the boiling point, freezing point, and other properties of the solution. The effective concentration (activity) of an ion in a high ionic strength solution is usually less than the total number of moles in the solution. The activity of an ion is calculated by multiplying its molal concentration by its activity coefficient. In very dilute solutions, activities and molal concentrations are essentially equal.

acute exposure
Contact with a substance that occurs once or for only a short time (up to 14 days [for humans]).

Source: ATSDR  Glossary of Terms

acute toxicity
Any poisonous effect produced within a short period of time following exposure, usually up to 24-96 hours, resulting in biological harm and often death.

Adamsite (DM) is an organoarsenic compound developed near the conclusion of World War I. The chemical warfare compound is solid when pure, and has been used as an aerosol dispersed by thermal grenades or smoke generators. Its effect are: severe irritation of the eyes, nose, and throat. If the agent is inhaled for 1-2 minutes, tightness of the chest and headache are experienced. The headache develops into general nausea, which can result in vomiting in approximately three minutes. Under concentrations expected to occur under combat conditions, fatalities are not expected; however, these compounds can be fatal at higher concentrations.
DM was discovered by German scientists in 1913 (Ger. pat. appl. 281049, July 1913 to F. Bayer and Co.), but was never used by Germany. It was independently discovered by Major Robert Adams working at the university of Illinois and also by a British team, both at the beginning of 1918. DM was produced, but not used, by the Americans at the end of the war; Franke states that "according to very incomplete reports [it] was used by the Italian Army." It was produced by many nations for use as a riot control agent until it was superseded by alpha-chloroacetophenone (CN) and similar tear agents. It was also found to be effective as a pesticide against marine borers, which kept in production for years. By 1920, gas mask filters had been improved to protect against aerosol particles, which may account for the termination of this line of development.
Names: DM, 10-Chloro-5,10-dihydrophenarsazine, Adamsite
Molecular formula:  C12H9AsClN
CAS Registry Number: 578-94-9

A new chemical species AB, each molecular entity of which is formed by direct combination of two separate molecular entities A and B in such a way that there is change in connectivity, but no loss, of atoms within the moieties A and B. Stoichiometries other than 1:1 are also possible, e.g. a bis-adduct (2:1). An intramolecular adduct can be formed when A and B are groups contained within the same molecular entity. This is a general term which, whenever appropriate, should be used in preference to the less explicit term complex. It is also used specifically for products of an addition reaction.

source:  IUPAC Gold Book

adduct ion
An electrically charged species formed by non-covalent attachment between an ion and a neutral species. These are most commonly observed in desorption and API and CI ion sources where a molecule of a component in the solvent or reagen gas remains attached to the ion.   

Source: A. Mallet, S. Down, Dictionary of   Mass Spectrometry, Wiley, 2010

Adenosylcobalamin  is a cobalamin derivative in which the ß-substituent is deoxyadenosyl (see the red ligand in left figure). It is one of two metabolically active forms synthesized upon ingestion of vitamin B12 and is the predominant form in the liver; it acts as a coenzyme in the reaction catalyzed by methylmalonyl-CoA mutase.

Cobalamins are coenzymatically active forms of vitamin B12
(cyanocobalamin) which is a water-soluble vitamin and a
nutrient essential for all cells.   Cobalamin is a substituted corrin-Co(III) complex (see blue structure in left figure) in which the cobalt atom is bound to the four nitrogen atoms of the corrin ring, an axial group R and 5,6-dimethylbenzimidazole (DMBI, see green part in left figure). The latter is linked to the cobalt by the N-3 nitrogen atom and is bound to the C-1 carbon of a ribose molecule by the N-1 nitrogen atom. Various forms of the vitamin are known with different R groups such as R = CN, cyanocobalamin; R = OH, hydroxocobalamin; R = CH3, methylcobalamin; R = adenosyl, coenzyme B-12 (shown here). 

Adenosylselenohomocysteine is a metabolite within the selenium metabolic pathway.
Formula C14H20N6O5Se
Mass 432.066

Adenosylselenomethione is a metabolite within the Se metabolic pathway.
Formula C15H24N6O5Se  
CAS Registry No.   5134-38-3
Chemical Synonym: AdoSeMet
Molecular Weight: 447.349 g/mol

Adenylylselenate is the first metabolite in the metabolism of Se in plants. The first step is the activation of selenate by ATP sulfurylase to form 5'-adenylylselenate

ADI (acceptable daily intake)
An estimate of the amount of a substance in food or drinking water, expressed on a body-weight basis, that can be ingested daily over a lifetime without appreciable risk (standard human = 60 kg). The ADI is listed in units of mg per kg of body weight.

adiabatic ionization
Process whereby an electron is removed from an atom, ion, or molecule in its lowest energy state
to produce an ion in its lowest energy state.

A solid material that removes chemical species from liquids or gases by causing them to adhere onto its surface (compare with absorbent and sorbent).

Adsorption is the enrichment (positive adsorption. or briefly, adsorption) or depletion (negative adsorption) of one or more components in an interfacial layer.

adsorption chromatography
A chromatographic method in which the molecules are retained through the interaction of the polar functional groups of the sample components and the functional groups on the surface of the packing material.

adsorption complex
Adsorption complex is a molecular term used to denote the entity constituted
by the adsorbate and that part of the adsorbent to which it is bound.

adverse health effect
A change in body function or cell structure that might lead to disease or health problems.

Source: ATSDR  Glossary of Terms

Particles, solid or liquid, suspended in a gas typically air.

aerosol matrix-assisted laser desorption ionization
Aerosol matrix-assisted laser desorption ionization is a variant of MALDI in which a mixture of matrix and analyte is nebulized and the resulting particles irradiated with a laser to form ion.

affinity chromatography
- a technique in which a biospecific adsorbent is prepared by coupling a specific ligand (such as an enzyme, antigen, or hormone) for the macromolecule of interest to a solid support (or carrier). This immobilised ligand will interact only with molecules that can selectively bind to it. Molecules that will not bind elute unretained. The retained compound can later be released in a purified state.

Agency for Toxic Substances and Disease Registry
The Agency for Toxic Substances and Disease Registry (ATSDR) is an agency of the U.S. Department of Health and Human Services (HHS). As mandated by the federal superfund law, the agency assesses health risks from hazardous waste sites on the EPA's National Priorities List. ATSDR determines if additional health studies are needed at these sites, provides health advisories and publishes toxicological profiles on chemicals found at hazardous waste sites. ATSDR also maintains exposure registries of people exposed to certain substances.

(Source: ATSDR website  )

airborne particulates
Total suspended particulate matter found in the atmosphere as solid particles or liquid droplets. Chemical composition of particulates varies widely, depending on location and time of year. Airborne particulates include: windblown dust, emissions from industrial processes, smoke from the burning of wood and coal, and motor vehicle or non-road engine exhausts.

(in analytical chemistry) Known amount of a homogeneous material, assumed to be taken with negligible sampling error.
Note 1: The term is usually applied to fluids.
Note 2: The term aliquot is usually used when the fractional part is an exact divisor of the whole: the term aliquant has been used when the fractional part is not an aexat divisor of the whole ( e.g. a 15-ml portion is an aliquant of 100 ml). When an aliquot is taken of a laboratory sample or test sample or the sample is otherwise subdivided, the samples have been called split samples.

chemical classification of hydrocarbon groups attached to compounds: alkyl groups have carbon atoms arranged in chains and contain no double or triple bonds.

alkylating agent
Substance which introduces an alkyl substituent into a compound. (IUPAC) 

general term for the introduction of an alkyl group into a compound and is more specifically known as methylation, ethylation, propylation, butylation, etc., depending upon the alkyl group inserted.


Organic mercury compounds in which the mercury is attached to an alkyl group.

Other names Alkylmercurials; Alkyl Mercury Compounds; Mercury Compounds, Alkyl; Compounds, Alkylmercury; Compounds,

alpha bond
In discussing the fragmentation mechanism of an  ion, the bond adjacent to the site of ionisation is  frequently referred to as an alpha bond.   

alum adjuvant
An aluminum compound with immune adjuvant activity. This agent adsorbs and preciptates protein antigens in solution; the resulting precipitate improves vaccine immunogenicity by faclitating the slow release of antigen from the vaccine depot formed at the site of inoculation

Aluminium is the worlds most common metallic element. It constitutes about 8% of the Earth's crust. It occurs in various chemical forms (species) in most rocks and soils, in vegetation and is found in most water supplies and as part of dust particles in the air. Aluminium  is also present in all clays, making it an constituent of cooking vessels since earliest civilization. Evolution of human life and civilisation has developed in an aluminium rich environment.
While aluminium is abundant in the environment, the naturally occurring forms are usually stable and do not interact with the biological processes which go on in living organisms. Under acidic conditions, however, aluminium may be released from rocks and soils in a soluble form which can be absorbed by plants and animals. 

ambient mass spectrometry
A general term describing mass spectrometry in  which ionisation takes place at ambient pressure  and temperature, usually in the open air. Specific  types include DESI and DART.  

American Chemical Society
With more than 161,000 members, the American Chemical Society (ACS) is the world’s largest scientific society and one of the world’s leading sources of authoritative scientific information. A nonprofit organization, chartered by Congress, ACS is at the forefront of the evolving worldwide chemical enterprise and the premier professional home for chemists, chemical engineers and related professions around the globe. The programs and activities conducted by ACS today are the products of a tradition of excellence in meeting member needs that dates from the Society's founding in 1876." (Source: ACS website )

American Council on Science and Health
"The American Council on Science and Health, Inc. (ACSH) is a consumer education consortium concerned with issues related to food, nutrition, chemicals, pharmaceuticals, lifestyle, the environment and health. ACSH is an independent, nonprofit, tax-exempt organization.

The nucleus of ACSH is a board of 350 physicians, scientists and policy advisors - experts in a wide variety of fields-who review the Council's reports and participate in ACSH seminars, press conferences, media communications and other educational activities." (Source: ACSH website )

A lack of crystallinity or the regular extended threedimensional-order of the atoms in a solid

An electroanalytical technique based upon the measurement of the current flowing through the working electrode of an electrochemical cell.

- a compound that can be either an anion or a cation depending upon the pH of the solution in which it is.

amplifier noise
This can be of two kinds. White noise is random signal fluctuations whose power spectrum contains all frequencies equally over a specified bandwidth whereas in pink noise the frequencies diminish in a specified fashion over a specified range.

Accelerator mass spectrometry (AMS).  In this specialized method, atomic ions are formed from  the sample by charge stripping  in a very high voltage source,  usually coupled to a Van de  Graff accelerator. Accelerator  mass spectrometry is used for  low-level analysis of  14  C isotopes  in radiocarbon dating and biological tracer studies.

analogue-to-digital converter (ADC)
An electronic device, usually based on a semiconductor chip,  which samples an analogue signal, e.g. a voltage,  and converts it into a digitised form. Important  parameters include the number of bits that are  output, the speed of conversion and the accuracy  and precision.

analysis of variance (ANOVA)
A statistical technique by which the observed variance can be divided into components, such as within-run and between-run variance which make up the total variance observed for an analytical method. Commonly used for analysis of the data from a replication study to make estimates of within-run and total imprecision when the data has been carefully collected over a series of runs and days.

The specific compound, ion, or molecule that is being determined by an analytical method.

analytical bias
A measure of how far the analytical result generated with a particular method diverges from the 'true' or actual analyte concentration.

analytical column
Typically, the main column used in the HPLC system to separate sample components; often referred to as the "heart" of the HPLC system.The analytical column typically is in series with a short pre-column (guard) having the function of protecting the analytical column against negative effects of complex sample matrices.

analytical method
The overall, systematic procedure required to undertaken an analysis. It includes all stages of the analysis – not just the (instrumental) end determination.

analytical run
Generally defined by CLIA as an 8 hour to 24 hour interval during which control materials must be analyzed. According to CLSI C24, a run is “an interval (i.e., a period of time or series of measurements) within which the accuracy and precision of the measuring system is expected to be stable. In laboratory operations, control samples are analyzed during each analytical run to evaluate method performance, therefore the analytical run defines the interval (period of time or number of specimens) between evaluations of control results. Between quality control evaluations, events may occur causing the measurement process to be susceptible to variations that are important to detect.”

analytical sensitivity
The ability of an analytical method to detect small quantities of the measured component. Numerically characterized by determination of detection limit.

analytical specificity
The ability of an analytical method to measure only the sought-for analyte or measurand. Numerically characterized by determination of interferences and non-specific responses to other analytes or materials.

A negatively charged ion.

anion exchange capacity
The ability of a solid substance to adsorb anions. The anion exchange capacity of a material represents the total positive charge on the surface of the material and is generally expressed in milliequivalents per 100 grams of material (compare with cation exchange capacity).

anion-exchange chromatography
the ion-exchange procedure used for the separation of anions. Both resins and bonded phases are available for this mode. The tetralkylammonium group is a typical strong anion-exchange functional group. An amino group bonded on the rigid adsorbent surface would be the example of a weak anion exchanger (WAX).

The electrode where oxidation occurs in an electrochemical cell. It is the positive electrode in an electrolytic cell, while it is the negative electrode in a galvanic cell. The current on the anode is considered a positive current according to international convention; however, in electroanalytical chemistry the anodic current is often considered negative. Contrast with cathode.

Combined effect of two or more factors which is smaller than the solitary effect of any one of those factors. In bioassays, the term may be used when a specified effect is produced by exposure to either of two factors but not by exposure to both together.

1. Caused by or influenced by human activities.
2. Describing a conversion factor used to calculate a dose or concentration affecting a human that has been derived from data obtained with another species (e.g., the rat).

intended to prevent fouling of underwater structures (as the bottoms of ships)

antifouling paint
protective coating on the body of a ship to prevent fouling by e.g. bivalves

The capacity of a substance to induce the formation of antibodies or to elicit an immune response when injected into an animal.

Antimony is a chemical element in the periodic table that has the symbol Sb (Latin: stibium, meaning "mark") and atomic number 51. A metalloid, antimony has four allotropic forms. The stable form of antimony is a blue-white metalloid. Yellow and black antimony are unstable non-metals. Antimony is used in flame-proofing, paints, ceramics, enamels, a wide variety of alloys, electronics, and rubber.

Adsorbable Organic Halogens is a measurement often used in waste water testing to indicate the overall level of the halogens, fluorine, chlorine, bromine and iodine. This "sum parameter" comes from a standard analytical procedure, which gives no information on the source or nature of halogens present nor on their toxicity. It has the advantage of being simple to measure; alternative methods of measuring levels of individual compounds are complex and require costly equipment.

Atmospheric pressure chemical ionization (APCI). In this method of ionization, an aerosol of sample solution is sprayed at atmospheric pressure into a heated region in which a sharp metal pin held at high potential sustains a corona discharge. The action of the discharge on the solvent creates reagent ions that react with the neutral sample molecules to create protonated ions of the molecule. These ions then pass through a sampling aperture into the mass analyzer of the mass spectrometer.

appearance energy
The appearance energy (or appearance potential) is the lowest energy which must be imparted to the parent molecule to cause it to produce a particular specified ion. This energy, usually stated in electron volts, may be imparted by electron impact, by photon impact, or in other ways.
(Note: It is recommended that the term 'appearance energy' should replace the term 'appearance potential' and that the energy should be stated in SI units.)

Source: IUPAC

aqua regia
One part of nitric acid and three parts of hydrochloric acid; used chiefly to dissolve metals.

aqueous speciation
The partitioning of chemical components between various aqueous species in a solution: bare species (e.g. Ca++), ion pairs (e.g. CaCO30), and complexes (e.g. Fe(CN)63-).

a synthetic seawater medium specifically designed for studying metal-algae interactions

Prokaryotes lacking nucleus as bacteria but they are as different from bacteria as are humans. They represent an own evolutionary pathway. They live in extreme places with high temperatures.

array detector
Detector comprising several ion/photon collection elements, arranged in a line or grid where each element is an individual detector.

arsanilic acid

Arsanilic acid, 4-Aminophenylarsonic acid derived from orthoarsenic acid, is an arsenical antibacterial veterinary medicine used in the prevention and the treatment of swine dysentery.

An arsenate (compound) is some compound that contains the arsenate ion : AsO43- . Arsenate is much like phosphate. In acid conditions we have arsenic acid, H3AsO4; in weakly acid conditions we have the dihydrogen arsenate ion, H2AsO4-; in weakly basic conditions we have hydrogen arsenate ion HAsO42-; and finally, in basic conditions, the arsenate ion AsO43-.

Arsenic is a chemical element that has the symbol As and atomic number 33. Its Atomic Mass is 74.92. Its Ionic Charge is (3-). This is a notoriously poisonous metalloid that has many allotropic forms: yellow (molecular non-metallic) and several black and gray forms (metalloids) are a few that are seen. Three metalloidal forms of arsenic with different crystal structures are found free in nature (the minerals arsenic sensu strictu and the much rarer arsenolamprite and pararsenolamprite), but it is more commonly found as arsenide and arsenate compounds. Several hundred such mineral species are known. Arsenic and its compounds are used as pesticides, herbicides, insecticides and various alloys.

The most common oxidation states for arsenic are -3 (arsenides: usually alloy-like intermetallic compounds), +3 (arsenates(III) or arsenites, and most organoarsenic compounds), and +5 (arsenates(V): the most stable inorganic arsenic oxycompounds). Arsenic also bonds readily to itself, forming, for instance, As-As pairs in the red sulfide realgar and square As43- ions in the arsenide skutterudite. In the +3 oxidation state, the stereochemistry of arsenic is affected by possession of a lone pair of electrons.

Arsenic Crisis Information Centre
"Online focal point for the environmental health disaster in Bangladesh and West Bengal, India, where millions of people are drinking ground water heavily contaminated with arsenic. Site includes infobank of news articles, scientific papers, comprehensive links to other relevant sites, online forum, email newsletter, and local site search." (Source: ACIC website )

arsenic trioxide
As2O3: an inorganic arsenic compound; a by-product of metal smelting operations.
This small-molecule arsenic compound shows antineoplastic activity. The mechanism of action of arsenic trioxide is not completely understood. This agent causes damage to or degradation of the promyelocytic leukemia protein/retinoic acid receptor-alpha (PML/RARa) fusion protein; induces apoptosis in acute promyelocytic leukemia (APL) cells and in many other tumor cell types; promotes cell differentiation and suppresses cell proliferation in many different tumor cell types; and is pro-angiogenic.

Arsenicin A
Arsenicin A, As4O3(CH2)3 is a complex molecule containing four arsenic atoms in a cage-like structure. It's found in tiny quantities in the New Caledonian marine sponge Echinochalina bargibanti and is the first poly-arsenic compound to have been isolated from nature. Its role in the marine sponge remains unknown, partly because of the lack of detailed knowledge about the chemical structure.

Empirical formula: C3H6As4O3

An arsenide (compound) is a compound with arsenic in oxidation state -3. An arsenide ion is an arsenic atom with three extra electrons and charge -3.

In chemistry an arsenite is a chemical compound containing an arsenic oxoanion where arsenic has oxidation state +3. Examples of arsenites include sodium arsenite which contains a polymeric linear anion, [AsO2]n, and silver arsenite, Ag3AsO3, which contains the trigonal, AsO33− anion. The arsenite ion is sometimes called ortho-arsenite.

The salts of the arsenous acid H3AsO3.

organoarsenical (CH3)3As+CH2COO-, a major arsenic containing species in marine invertebrates and fish

organoarsenical (CH3)3As+CH2CH2OH, a major arsenic containing species in marine invertebrates and fish

Natural arsenolipids are analogues of neutral lipids, like monoglycerides, glycolipids, phospho- and also phosphonolipids. They have been found in microorganisms, fungi, plants, lichens, in marine mollusks, sponges, other invertebrates, and in fish tissues. Arsenolipids are thought to be end products of arsenate detoxification processes, involving reduction and oxidative methylation and adenosylation.

Valery M. Dembitsky, Dmitrii O. Levitsky, Arsenolipids,  Progress in Lipid Research,  43/5 (2004) 403-448. 

FeAsS, Iron Arsenide Sulfide, an inorganic arsenic compound. This mineral is a major ore of arsenic.

For more information on the mineral Arsenopyrite see: Mineral Gallery: The Mineral Arsenopyrite 

Arsenoribofuranosides are organoarsenicals containing a pentose moiety as part of their molecular structure (see figure), which explains why they are commonly referred to arsenosugars.
Arsenosugars are major arsenic compounds in algae but are reported to be present in significant concentrations in other marine organisms such as bivalves. This class of compounds has been raising growing concern since recent reports indicating the possibility of metabolizing arsenosugars to the carcinogenic dimethylarsinic acid (DMAA) by the human body.

High-purity arsine is exclusively used in semiconductor manufacturing. The arsenic atom is an n-type dopant for epitaxial silicon. Arsenic is introduced in the silicon wafer by diffusion or implantation techniques.
The presence of traces of arsine in the environment has been observed in gas purged from natural waters and in hot springs.
CAS Number : 7784-42-1
Other names: Arsenic hydride; Arsenic trihydride; Arsenous hydride; Hydrogen arsenide; Arsenic hydrid

chemical classification of hydrocarbon groups attached to compounds: aryl groups have carbon atoms arranged in aromatic rings.

Organoarsenic compounds in which arsenic is bound onto phenyl.  
The structures of the arylarsenicals that are approved as animal-food additives are shown below.
4-Hydroxy-3-nitrophenylarsonic acid (3-NHPAA) and  p-arsanilic acid (p-ASA) are approved for poultry and swine. 4-Nitrophenylarsonic acid (4-NPAA) and  p-ureidophenylarsonic acid (p-UPAA) are approved only for controlling blackhead disease in turkeys.
There are some compounds, such as Clark-1, Clark-2 and Adamsite, which have been developed during the first World War as warfare chemicals. Some of their degradation products (e.g. diphenyl arsinic acid) can also been found in the environment close to former production or dump sites.

The decomposition, prior to analysis, of organic matrix constituents of the sample. The most common ashing techniques are acid or alkali dissolution: alkaline fusion; and oxidation using either low-temperature oxygen plasma or muffle furnace. 

Sometimes used to mean a test or test result, but other times as a synonym for the analytical method.

asymmetrical flow field-flow fractionation
Asymmetrical flow FFF (AFFFF or AF4) is a type of flow FFF using only one permeable wall which serves as accumulation wall. Experiments show that the asymmetrical design separates faster and more efficient than the symmetrical channel.
AFFFF is certainly one of the most universal FFF techniques. It features a very broad (105) separation range from 1 nm to 100  µm . And its application range covers both simple and complex macromaterials of biological, pharmaceutical, industrial and environmental relevance such as proteins, polymers or nanoparticles.

atmospheric deposition
Process that transfers a chemical from the atmosphere to the Earth’s surface (land, water, or vegetation) by either dry impingement or by transport in rain or snow.
See also dry deposition, wet deposition.

atmospheric pressure ionization (API)
Atmospheric pressure ionization (API) is any process in which ions are formed from atoms or molecules at atmospheric pressue, such as in  ESI, APCI, APPI and MALDI.

atmospheric pressure photoionisation (APPI)
A form of API in which the analyte is sprayed into the source, as in ESI and APCI sources, in a  solvent frequently containing a dopant molecule such as toluene or acetone. The spray is irradiated by a powerful UV source that forms excited  species which undergo secondary ion/radical- molecule reactions with the analytes to cause ionisation. It is claimed to be the method of choice for detection of non-polar molecules in HPLC eluates. Protonated or deprotonated molecules or radical molecular ions can be formed, according to  the mechanisms and thermodynamics involved. 

atom gun
A device designed to produce a collimated beam of energetic atoms from a heated source. In MS, this is the prime source for the formation of ions in a FAB source. Most SIMS and FAB sources use atom as well as ion guns, commonly with xenon atoms or caesium ions.

atomic absorption spectrometry (AAS)
A spectroscopic technique that responds to free atoms in the gaseous phase. The diminuation in the intensity of analyte specific monochromatic radiation which is directed through the atom cloud is related to the quantity of analyte atoms present in that cloud.

atomic emission spectrometry (AES)
A group of spectroscopic techniques that respond to free atoms or ions in the gasepous phase. The intensity of the energy emitted as the analyte atoms/ions spontaneously return from an excited state(s) to their lowest energy state is related to the quantity of that analyte.

atomic fluorescence spectrometry (AFS)
In atomic fluorescence spectrometry (AFS), ground state atoms created chemically or thermally in a hydrogen flame or quartz tube furnace, are excited by a beam of light. In difference to AAS measuring the absorbed light, the emission resulting from the decay of the excited state is measured. AFS is a very specific element detection technique but requires a high output, high stability light source.

atomic spectroscopy
The analytical principle of atomic spectroscopy is based on the property of atoms of emitting or absorbing element-specific electromagnetic radiation under certain physical conditions. To this end, it is necessary to release the elements to be investigated in a sample from their compounds, generally by the input of energy, and to make them available as free particles.

atomic weight
The nominal atomic weight of an isotope is given by the sum of the number of neutrons and protons in each nucleus. The exact atomic weight differs fractionally from that whole number, because neutrons are slightly heavier than protons and the mass of the nucleus is also affected by the binding energy.

Conversion of molecular or condensed forms of an analyte into free atoms.

Auger electron spectroscopy (AES )
An electron beam technique applied for near-surface elements identification often used in thin film science.

Auranofin is a metallodrug used in treating inflammatory arthritis. Exactly how such gold compounds work is not well understood. In patients with inflammatory arthritis, such as adult and juvenile rheumatoid arthritis, gold salts can decrease the inflammation of the joint lining.

Autism is a brain disorder that affects a person’s ability to communicate, relate to others, and interact with his or her surroundings. Autism is usually diagnosed between the ages of two and three based on observation of  behaviour. There is no cure for autism, except early diagnosis and treatment, which may help to ease the symptoms.

Self-catalyzed oxidation reaction that occurs spontaneously in an aerobic environment.

average mass
The average mass of an ion of a known empirical formula is calculated by summing the relative average atomic mass of each atom present. For example, carbon has an average atomic mass of 12.01115 Da, hydrogen is 1.00797 Da, and so on. The average mass of the molecular ion of a chemical compound is also the mass that appears on the bottle. However, in a stick representation of a mass spectrum, there is no ion signal at the average mass. Instead, signals appear for ions of various isotopic compositions. The average mass corresponds to the center of the centroid signal recorded for higher mass ions at lower instrumental resolutions.

Azocyclotin is an organotin compound used as an insecticide. The product is a contact acaricide.

IUPAC: tri(cyclohexyl)-1H-1,2,4-triazol-1-yltin
Reg. No.: 41083-11-8

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