期刊
ANALYTICAL AND BIOANALYTICAL CHEMISTRY
卷 408, 期 2, 页码 651-655出版社
SPRINGER HEIDELBERG
DOI: 10.1007/s00216-015-9127-y
关键词
Solid-state (CNMR)-C-13; Phase-adjusted side band suppressing (PASS); Cross polarization/magic angle spinning (CPMAS); Direct polarization (DPMAS); Carbon functional groups; Humic substances
资金
- Japan Society for the Promotion of Science [20380043]
- Grants-in-Aid for Scientific Research [20380043] Funding Source: KAKEN
The composition of carbon (C) functional groups in natural organic matter (NOM), such as dissolved organic matter, soil organic matter, and humic substances, is frequently estimated using solid-state C-13 NMR techniques. A problem associated with quantitative analysis using general cross polarization/magic angle spinning (CPMAS) spectra is the appearance of spinning side bands (SSBs) split from the original center peaks of sp (2) hybridized C species (i.e., aromatic and carbonyl C). Ramp CP/phase-adjusted side band suppressing (PASS) is a pulse sequence that integrates SSBs separately and quantitatively recovers them into their inherent center peaks. In the present study, the applicability of ramp CP/PASS to NOM analysis was compared with direct polarization (DPMAS), another quantitative method but one that requires a long operation time, and/or a ramp CP/total suppression side band (ramp CP/TOSS) technique, a popular but non-quantitative method for deleting SSBs. The test materials were six soil humic acid samples with various known degrees of aromaticity and two fulvic acids. There were no significant differences in the relative abundance of alkyl C, O-alkyl C, and aromatic C between the ramp CP/PASS and DPMAS methods, while the signal intensities corresponding to aromatic C in the ramp CP/TOSS spectra were consistently less than the values obtained in the ramp CP/PASS spectra. These results indicate that ramp CP/PASS can be used to accurately estimate the C composition of NOM samples.
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