التفاصيل البيبلوغرافية
| العنوان: |
SUITABILITY OF DIFFERENT [sup13]C SOLID-STATE NMR TECHNIQUES IN THE CHARACTERIZATION OF HUMIC ACIDS. |
| المؤلفون: |
Jingdong Mao, Weiguo Hu, Guangwei Ding, Schmidt-Rohr, Klaus, Davies, Geoffrey, Ghabbour, Elham A., Baoshan Xing |
| المصدر: |
International Journal of Environmental Analytical Chemistry; 2002, Vol. 82 Issue 4, p183, 14p, 1 Chart, 1 Graph |
| مصطلحات موضوعية: |
HUMIC acid, SOLIDS, CARBONYL compounds, SPECTRUM analysis, QUANTITATIVE chemical analysis |
| مستخلص: |
Qualitative and quantitative analyses of humic acids (HAs) with five different [sup13]C solid-state NMR techniques were assessed using HAs of various origins and locations. The NMR techniques compared are: (1) direct polarization/magic angle spinning (DP/MAS) at 13 kHz, (2) conventional cross polarization (CP)/MAS at 5kHz, (3) ramp-CP/MAS at 8kHz, (4) CP/total sideband suppression (TOSS) at 4.5kHz, and (5) DP/ MAS corrected by CP/spin-lattice relaxation with TOSS. The spectra from the five techniques were first compared qualitatively. Then, each spectrum was divided into eight regions for quantitative evaluation. DP/MAS spectra were used as quantitative references. Ramp-CP/MAS and CP/TOSS spectra gave consistently better results than those of the conventional CP/MAS spectra at a [sup13]C frequency of 75 MHz, which were incorrect due to spinning sidebands. CP/MAS at low magnetic fields (22.6 and 50.6 MHz [sup13]C frequency) indicated improved integration results but lower resolution. Correction factors calculated by comparison with DP/MAS will be useful to convert the non-quantitative peak areas in the CP/'FOSS and ramp-CP/MAS spectra into more quantitative results. [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
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