Advancement per volume

high-resolution terminology - matching measurements at high-resolution

Advancement per volume

Description

Advancement per volume or volume-specific advancement, d_trY [mol∙V^-1], is related to advancement, d_trY = d_trξ∙V^-1, as is the amount of substance per volume, c_i (concentration [mol∙V^-1]), related to amount, c_i = = n_i∙V^-1. Advancement per volume is particularly introduced for chemical reactions, d_rY, and has the units of concentration. In an open system at steady-state, however, the concentration does not change as the reaction advances. Only in closed systems, specific advancement equals the change in concentration divided by the stoichiometric number,

ΔrY = Δci/νi (closed system) 

ΔrY = Δrci/νi (general) 

In general, Δc_i is replaced by the partial change of concentration, Δ_rc_i (a transformation variable or process variable), which contributes to the total change of concentration, Δc_i (a system variable or variable of state). In open systems at steady-state, Δ_rc_i is compensated by external processes, Δ_extc_i = -Δ_rc_i, exerting an effect on the total concentration change,

Δci = Δrci + Δextci = 0 (steady state)

Δci = Δrci + Δextci (general)

Abbreviation: d_trY

Reference: Gnaiger (1993) Pure Appl Chem

Communicated by Gnaiger E 2018-10-19

Application in respirometry

In typical liquid phase reactions the volume of the system does not change during the reaction. When oxygen consumption (ν_O2 = -1 in the chemical reaction) is measured in aqueous solution, the volume-specific oxygen flux is the time derivative of the advancement of the reaction per volume [1], J_V,O2 = d_rY_O2/dt = d_rξ_O2/dt∙V^-1 [(mol∙s­^-1)∙L­^-1]. The rate of O₂ concentration change is dc_O2/dt [(mol∙L­^-1)∙s­^-1], where concentration is c_O2 = n_O2∙V^-1. There is a difference between (1) J_V,O2 [mol∙s­^-1∙L­^-1] and (2) rate of concentration change [mol∙L­^-1∙s­^-1]. These merge to a single expression only in a closed system. In open systems, internal transformations (catabolic flux, O₂ consumption) are distinguished from external flux (such as O₂ supply). External fluxes of all substances are zero in closed systems [2].

MitoPedia concepts: Ergodynamics 

MitoPedia methods: Respirometry 

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