Concentration

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Concentration

Description

Concentration [mol·L^-1] or density is a volume-specific quantity, expressing the number of particles per volume, the amount of substance per volume, or generally matter in a variety of formats (count, amount, charge, mass, volume or energy) per volume of the system. In solution chemistry, amount concentration is amount, n, of B per volume, V, of the solution, c_B = [B] = n_B·V^-1 [mol·dm^-3]=[mol·L^-1]. The standard concentration, c°, is defined as 1 mol·L^-1 = 1 M. A change of concentration of an elementary entity, X, dc_X, in isolated or closed systems at constant pressure is due to internal transformations (advancement per volume) only. In closed compressible systems (with a gas phase), the concentration of the gas changes, when pressure-volume work is performed on the system. In open systems, a change of concentration can additionally be due to external flow across the system boundaries.

Abbreviation: c [mol·L^-1]; C [x·L^-1]

Reference: IUPAC Gold Book

Communicated by Gnaiger E 2018-10-18 (last update 2020-05-18)

IUPAC definition

Concentration {quote}:

1. Group of four quantities characterizing the composition of a mixture with respect to the volume of the mixture (mass, amount, volume and number concentration).

2. Short form for amount (of substance) concentration (substance concentration in clinical chemistry).

{end of quote: IUPAC Gold Book}

Concentration in different formats

Concentration is a quantity, X, of objects, X, per volume, V, of the system. The entities X have to be specified in the text or indicated by a subscript or in parentheses: C_N(X).

Concentration	Symbol	Definition	Unit	Note
Count concentration	CN	= NX·V-1	[x·L-1]	1
Amount concentration	cn(X) = cB	= nX·V-1	[mol·L-1]	2
Charge density	ρe	= QX·V-1	[C·L-1]	3
Mass density	ρX	= mX·VX-1	[kg·L-1]	4
Volume density	ΦX	= VX·V-1	[L·L-1]	5

1. The IUPAC term 'number concentration' should be replaced by 'count concentration' (or 'number of entities concentration').
2. Amount concentration is a counting concentration, converting the counting unit [x] into moles [mol] using the Avogadro constant.
3. Charge density in electricity is charge per volume. Charge density is a counting concentration, converting the counting unit [x] into coulombs C using the elementary charge, or converting moles [mol] into coulombs [C] using the Faraday constant.
4. Mass density is mass of X per volume of X, V_X; ρ_X is the reciprocal of specific volume.
5. Volume density is equivalent to the volume fraction.

Total concentration

1. The total concentration of a substance (e.g. ADP) must be distinguished from the concentration of a specific ionic species (e.g. ADP^4-, MgADP^2-, MgHADP^-).
2. The total concentration of a substance must be distinguished from the free concentration, if unspecific binding occurs to membranes (e.g. TPP) or if a substance is bound to BSA (e.g. fatty acids).
3. The concentration of a substance (c) differs from the activity (a), except for dissolved gases and at very high dilution. The activity of dissolved gases is expressed as the (relative) partial pressure, e.g. p_O2). The ratio of concentration, e.g. c_O2 [µM], and partial pressure, e.g. p_O2 [kPa], is the solubility (see oxygen solubility, S_O2).

References

Bioblast link	Reference	Year
Bureau International des Poids et Mesures 2019 The International System of Units (SI)	Bureau International des Poids et Mesures (2019) The International System of Units (SI). 9th edition:117-216. ISBN 978-92-822-2272-0	2019
Cohen 2008 IUPAC Green Book	Cohen ER, Cvitas T, Frey JG, Holmström B, Kuchitsu K, Marquardt R, Mills I, Pavese F, Quack M, Stohner J, Strauss HL, Takami M, Thor HL (2008) Quantities, Units and Symbols in Physical Chemistry. IUPAC Green Book 3rd Edition, 2nd Printing, IUPAC & RSC Publishing, Cambridge.	2008
Gnaiger 2020 BEC MitoPathways	Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Bioenerg Commun 2020.2. https://doi.org/10.26124/bec:2020-0002	2020
Gnaiger 2020 MitoFit x	Gnaiger E (2021) The elementary unit — canonical reviewer's comments on: Bureau International des Poids et Mesures (2019) The International System of Units (SI) 9th ed. https://doi.org/10.26124/mitofit:200004.v2	2021
BEC 2020.1 doi10.26124bec2020-0001.v1	Gnaiger E et al ― MitoEAGLE Task Group (2020) Mitochondrial physiology. Bioenerg Commun 2020.1. https://doi.org/10.26124/bec:2020-0001.v1	2020

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Concentration

» Volume

» Activity

» Concentration

» Density

» Mole

» Molar mass

Pressure

» Barometric pressure

» Chemiosmotic pressure

» Gas pressure

» Osmotic pressure

» Oxygen pressure

» pascal

» Pressure

Solubility = concentration/pressure

» Solubility

» Solubility factor

» Oxygen solubility

General

» Boltzmann constant

» Energy

» Force

» Gas constant

» Work

Related keyword lists

» Keywords: Oxygen signal

» Keywords: Normalization

MitoPedia concepts: MiP concept, Ergodynamics