The data can be further simplified by performing a second order difference ∆∆S ). This second order difference then reports on a single correlation between the first nuclei that was substituted (H/D on the TMA) and the second nuclei (H/D on acetate), see Figure . Due to strong inelastic scattering from 1 H and the Placzek effect, hydrogen-rich samples exhibit significant background, especially in light water H 2 O, see Figure . This effect is significantly reduced in heavy water D 2 O. The inelastic scattering scales with 1 H atomic concentration, so the first-order differences should display the same Placzek background, which disappears in the second-order difference. After the background subtraction (See Figure ) and terminating the data using a window function up to 6 Å-1 for the two second order differences, the constant value in the last figure confirms the absence of background and indicates consistent chemical composition across the solutions.