All compounds were weighed on an analytical balance (Mettler Toledo XS105), so that the amount of moles could be computed without having to take into account densities and density changes. Clear solutions were obtained through shaking, vortex and sonication. The NMR tubes were filled with 500 µL of the solution to allow optimal shimming of the sample. Prior to initiating the measurement, the NMR tube was wiped clean with a paper tissue. Relevant signals of the linker and the internal standard, maleic acid, were integrated in an unbiased way by the following two steps: 1. The peak center frequency and full-width at half maximum (FWHM) were determined with the peakw command, 2. The integration range was then defined by multiplying this FWHM by 18, ensuring the peak center was at the center of the integration range. Simultaneously, the signal-to-noise ratio (SINO) of the 2-MeIm methyl signal was computed to ensure sufficiently a small error on the integrated signal due to insufficient signal intensity. Next, the integration values were normalized to their respective number of equivalent protons. Finally, the calculated ratios between the normalized integration values of the respective linker and MA were compared with the expected ratios based on their relative concentrations as determined from the sample preparation.