Ddr2 500 mhz nmr spectrometer

Epoxy contents of epoxidized lignin samples were measured by ¹H NMR according to a previously reported method.^[64] Each epoxidized lignin sample (ca. 50 mg) was dissolved in 700 μL of deuterated dimethyl sulfoxide ([D₆]DMSO). As an internal standard, 1,1,2,2 tetrachloroethane (20 mg) was added. NMR analysis was performed using an Agilent DDR2 500 MHz NMR spectrometer equipped with 7600AS, running VnmrJ 3.2 A, with a 10 s relaxation delay, and 64 scans. The epoxy content of each epoxidized lignin was calculated based on the ratio of following peaks δ [ppm, [D₆]DMSO]: 2.77 (m, 1H); 2.92 (m, 2H); 3.41 (m, 1H), 4.32 (dd, 1H), and 4.64 (m, 1H); these peaks are assigned to the epoxy ring chemical shifts and peaks of internal standard (6.89 ppm, S, 1H). In addition, the average number of epoxy groups in each macromolecule was calculated according to the following Equation 2: ${\displaystyle \bar{n}=\mathrm{epoxy}\mathrm{content}\left(\mathrm{mol}\mathrm{g}{}^{-1}\right)\times M{}_{\mathrm{n}}}$