Is it possible to save the Euler rotations as Quaternions without loss of data? Long story short is that, that I made an animation using Euler rotation but during cleaning the graph I realized that the graph and the axis got mixed up, eg. x and y axis both gave more or less the same sort of rotation in the graph but in the 3D space on rotating along local axis I get a completely different type of rotation.
I usually do my animations with Quaternions, but this time, due to some issues I switched to Eulers without understanding how they work. Now I have a ton of animation data and a big mess cleaning up the graphs.

So my question is:

Is it possible to save the Euler rotations as Quaternions without loss of data (visual data at least)? 

If that's not possible, then I should ask for the work around the graph editor so that the axis move according to the actual axis movements.

EDIT: I am presently using ZYX Euler rotation if that helps
In 2.79 there's an addon that works very well, called Quat/Euler rotation mode converter.