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Quantitative Methods: Part 1. Solutions and Dilutions

Author(s): David R. Caprette, PhD

Volume/volume (V/V) Solutions

Volume-in-volume is another common way of describing a solution. We simply describe the percent total volume contributed by the liquid solute. As with the other types of formulas used in biology, we assume that the solvent is water unless some other solvent is specified.

V/V often is used to describe alcohol solutions used for histology or for working with proteins and nucleic acids. For example, 70% ethanol is simply 70 parts pure ethanol mixed with water to make 100 parts total. To make a liter of such a solution we would start with 0.7 L absolute ethanol and bring the final volume to 1 liter with water. More often, we might find ourselves with 95% alcohol. To make a 70% solution from a 95% stock solution requires a little more calculation. We will talk about that later, when we discuss how to make dilutions.

Destaining of protein gels refers to the soaking of a stained gel in acidified alcohol to remove all dye that is not bound to proteins, thus revealing the bands. A useful destaining solution consists of 7% methanol and 10% acetic acid.  This means using 100 ml pure (or "glacial") acetic acid and 70 ml methanol per liter of final solution.