Hello everyone,
I would like to do UPLC. In the protocol there is 0.2% aqueous formic acid and 0.2% formic acid in methanol. what is aqueous means and how do we prepare them?
Thank you for your help
0.2% aqueous formic acid (FA) is a solution of FA in water. 0.2% of the total volume is FA.
Example to get 1ml of that solution: add 2µl of FA in 998µl water.
Same logic for the 0.2% FA in methanol, but you have to use methanol instead of water.
in reality it should say whether it 0s 0.2 % volume by volume (which is what Jonathan describes) or weight by weight 2 g in 1 kg.
Practically it is not super important as long as you do it exactly the same way each time.
To prepare 0.2% of formic acid in ethanol.
1. Get pure absolute ethanol, if the formic acid is in crystal form, measure out 0.2g using electronic balance, then dissolve in 100cm3 of the absolute ethanol.
2. If the formic acid is in solution, measure out 0.2cm3 using measuring cylinder, dilute with absolute ethanol to 100cm3.
In all use standard volumentric flask.
I. Concentrations are typically given in a solute to solution basis. A rare exception to this trend is molality (mol solute / kg solvent). Solubilities can be given in either a solution basis, or a solvent basis. Weight (i.e. mass) percentage concentrations (denoted: wt%, wt.%, w/w%, m/m%) should in principle be understood as referring to the mass of solution, which is the denominator of the underlying fraction. Even if just denoted by the % symbol, % concentrations, namely those indicated in commercial labels, should generically be assumed as given in wt%, unless otherwise stated or if there are good reasons to suppose otherwise.
II. Weight (mass) formulation ratios are not to be confused with weight (mass) percentage concentrations, since the denominator refers then, in principle, to one of the components mixed; most often either the major component and/or that considered as the solvent for the added component, to which the numerator usually refers. Formulation ratios can be also given in weight (mass) to volume basis, or on a volume to volume basis.
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