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. Author manuscript; available in PMC: 2021 Sep 1.
Published in final edited form as: Anal Bioanal Chem. 2020 Jul 3;412(24):6211–6220. doi: 10.1007/s00216-020-02792-5

Fig. 3.

Fig. 3

Validation of ninhydrin assay versus 1H NMR using GelNB. (a) Full NMR spectra of GelNB synthesized with carbic anhydride (GelNB-CA), GelNB synthesized via NHS conjugation (GelNB-NHS), and non-functionalized gelatin. Integration ranges for the functional group peak and internal standard are highlighted in gray and pink, respectively. (b) Structures and peak assignments for protons in the norbornene functional group in GelNB-CA and GelNB-NHS [7]. (c) Fractional DoF values determined by 1H NMR versus the optimized ninhydrin assay for five GelNB-CA samples (black dots) and one GelNB-NHS sample (open circle). Mean ± std dev of n = 3 technical replicates of ninhydrin assay; some error bars too small to see. Dotted line shows linear regression, y=0.9770x – 4.847, R2=0.87 Grey line shows the ideal scenario, y=x.