Plot other data over contour line

I have a vtk file of a droplet with the concentration contour (C11) and the some other data. using the ‘contour’ option I was able to get a contour of the droplet interface. But I need to plot the arc length of the droplet versus the surfactant concentration (C11) along the interface. Using ‘plot over sorted lines’ only gives me the arc length information. How do I plot surfactnat concentration (C12) wrt arc length? I’m attaching the vtk file here. Thanks in advance for your help.

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