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A solution is {Quote}: A liquid or solid phase containing more than one substance, when for convenience one (or more) substance, which is called the solvent, is treated differently from the other substances, which are called solutes. When, as is often but not necessarily the case, the sum of the mole fractions of solutes is small compared with unity, the solution is called a dilute solution. A superscript attached to the ∞ symbol for a property of a solution denotes the property in the limit of infinite dilution {end of Quote: IUPAC Gold Book}. » MiPNet article

Reference: IUPAC Gold Book

Stock-, storage- and working-solutions: How do they differ?

Publications in the MiPMap
Gnaiger E (2014) Stock-, storage- and working-solutions: How do they differ? Mitochondr Physiol Network 2014-04-17.

Oroboros (2014) MiPNet

Abstract: This is an attempt to clarify the terms stock-, storage-, commercial- and working-solutions for improved consistency in relevant protocols.

β€’ O2k-Network Lab: AT Innsbruck Gnaiger E

Final concentration of a substance X

The final concentration, cX, of a compound (often substance X is a dissolved substance in solution, i.e. a solute) is the concentration of X in solution used in the experimental chamber (experimental measurement system), at a dilution that depends on the concentration of the stock solution, the volume of stock solution titrated or added (v) into the experimental chamber, and the volume of the experimental chamber (V). The final concentration, cX,t, may change in the course of an experiment over time t, if the substance is a substrate or product of chemical reactions. Subsequent titrations or continuous injections of other solutions induce a further dilution, cX,t, in the experimental system. At steady state, continuous external flows of substance X (injections and outflow at constant volume) compensate for internal reactions involving transformations of the substance X (cX,t = const.).

Β» More information: concentration.

Stock solution and stock concentration of substance X

A stock solution is used as a stock during the experiment, for filling titration syringes and additions to the experimental chamber. The stock solution differs from the storage solution, if it has to be prepared fresh (without the option of storage) from a storage solution. The stock concentration, cX,stock, is diluted to the final concentration in the chamber. At the limit of filling the entire chamber with stock solution, the stock concentration and final concentration are identical.

Storage solution and storage concentration of substance X

A storage solution is the solution used for storage. There may be different storage concentrations, if various dilutions can be stored. In specific cases, the storage concentration of X in the storage solution may be equal to the stock concentration, if the stock solution can be stored.

Commercial stock and commercial solution

The commercial stock is frequently a dry powder, or a commercial solution. Commercial stocks are appropriate for storage according to the suppliers specifications. Once opened, storage conditions and maximum storage time of a commercial stock may change. For some chemicals the entire commercial stock may have to be used at once for preparation of a storage solution or stock solution.

Working solution and working concentration

Working concentration is an ambiguous term. Clarification is required if the working concentration refers to the final concentration in the experimental chamber in which the experimental work is performed, or if it refers to the stock concentration with which titrations are performed. Perhaps working solutions should be considered to comprise all dilutions obtained in stock solutions and the final solution, which collectively are contrasted to storage and commercial solutions. For the sake of clarity, the use of 'working concentration' is discouraged, except if such concentrations refer explicitely to different dilution steps in working solution A, working solution B, etc., which yield a final storage solution or actual stock solution, as defined above.

Terminology in the Bioblast wiki

  • In various protocols described on the Bioblast wiki, clarification and updates are required to provide consistent information on commercial, storage and stock solutions and their respective concentrations.
  • Compare: Substance X and metabolic control variable, X. X indicates the type of a substance, whereas X is the quantity including effects of the concentration of X and of the composition in the system on X (at a given temperature and pressure; Gnaiger 1993).
  • Chemical storage solutions must be clearly distinguished from clinical organ storage solutions or preservation solutions (e.g. BIOPS for the storage of tissues or mt-preparations (Gnaiger 2000 Life in the Cold).

MitoPedia concepts: MiP concept, Ergodynamics 


HRR: Theory 

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