无谱峰畸变的定量13C DEPT++谱研究

具有定量特征的极化转移¹³C NMR 因检测灵敏度和分辨率高而常用于有机物的NMR 定量分析，比如Q-DEPT、Q-DEPT⁺等．但是，DEPT 检测本身存在相位和多重峰畸变问题，可能造成复杂样品的定量测定困难．由于DEPT++技术能够有效地消除上述畸变，该文尝试将Q-DEPT⁺方法的定量技术扩展到DEPT⁺⁺中，以消除谱峰畸变对于定量的影响．首先，利用积算符对DEPT⁺⁺的极化转移机制进行了系统理论分析，结果发现目前标准仪器和文献中关于DEPT⁺⁺可观测算符的表达式中存在符号错误，实验结果进一步证实了我们的猜测；进而采用Q-DEPT⁺技术中所采用的多极化转移时间和读出脉冲技术，将DEPT⁺⁺用于定量测定．结果表明所建立的Q-DEPT⁺⁺方法能够有效地消除谱畸变问题．

Distortionless Quantitative 13C DEPT++Experiment

Polarization transfer 13C NMR techniques, such as DEPT and its modified versions (i.e., DEPT++, Q-DEPT and Q-DEPT+), are frequently used in the analysis of complex mixture, given its high sensitivity and resolution. However, the practical use of quantitative DEPT experiments are often hampered by spectral distortions, which makes accurate quantification difficult. In this study, we incorporated elements of the Q-DEPT sequence into the DEPT++pulse sequence, with the aim to eliminate spectral distortions in Q-DEPT+. The polarization transfer mechanisms underlying DEPT++were analyzed. It was found that it is possible to obtain distortionless spectrum in quantitative DEPT++experiment simply by calibrating the flip angle of the read pulse.