In most reversed phase HPLC separations today, acetonitrile
is the organic solvent of choice. However, I found that use of acetone instead can
have many advantages. In preparative chromatography, acetone is more volatile
and therefore it is easier to obtain product from a collected fraction. In
addition, its lower cost compared to acetonitrile translates to significant savings
at the preparative scale. In analytical applications, it can be used as a means
to change elution order in the case of some analytes. Sometimes the peak shape
or efficiency may even be superior.
I
investigated the separation of a variety of test solutes using either
acetonitrile or acetone. Due to the high UV cutoff of acetone, I selected
analytes with strong absorption in the high UV/visible range. These analytes typically
have a high degree of conjugation, such as dyes. If you’re not using a UV-based
detection method though, acetone won’t be a problem for analysis of an analyte
with little or no UV absorption. An example of this is our study of amino acids using
acetone with LC-MS.
In
2008–2009, there was a worldwide shortage of acetonitrile that prompted studies
of alternative solvents. Often, methanol was found to be the next best choice,
but it has its own drawbacks as well. In terms of safety, its toxicity is
higher than acetone. Chemically, acetone is more similar to acetonitrile than
methanol since both are polar aprotic solvents. For this reason, you could
predict that in general retention using acetone would be comparable to
acetonitrile in many instances. I found this to be the case for four of the
five test solutes I tested, which showed very similar retention (Fig. 1).
Fig. 1
