A mobile phase used for a separation by reversed-phase liquid chromatography (RP
ID: 954121 • Letter: A
Question
A mobile phase used for a separation by reversed-phase liquid chromatography (RPLC) consists of 70.0% isopropanol, 15.0% ethyl acetate, and 15.0% dioxane (v/v). Determine the solvent polarity index, P, for this mobile phase. A list of solvent polarity indexes for various liquids can be found here.
A mobile phase used for a separation by reversed-phase liquid chromatography (RPLC) consists of 70.0% isopropanol, 15.0% ethyl acetate, and 15.0% dioxane (v/v). Determine the solvent polarity index, P, for this mobile phase. A list of solvent polarity indexes for various liquids can be found here Number P= If the mixture consists of only isopropanol and dioxane, what percent of each solvent is required to produce a mobile phase of the same solvent polarity index? Number isopropanol Number % dioxaneExplanation / Answer
The polarity index for 70.0% isopropanol, 15.0% ethyl acetate, and 15.0% dioxane :
PAB = isopropanol P isopropanol + ethyl acetate P ethyl acetate+ dioxane P dioxane
= % of solvent ,
PAB = 0.70* 3.92 + 0.15*4.4+ 0.15*5.27
PAB = 2.744+0.66+0.7905
PAB = 4.1945 or 4.20
Now PAB = isopropanol P isopropanol + dioxane P dioxane
4.19 = 0.80* 3.92 + 0.20*5.27
4.19= 3.136+1.054
isopropanol = 80% and dioxane =20%
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