Quantitative Refocused INEPT Method Based on Simulated Annealing Optimization

Abstract

In this paper, we presented a quantitative refocused INEPT (Refocused Insensitive Nuclei Enhanced by Polarization Transfer) method based on simulated annealing optimization, which utilizes the optimized polarization transfer and refocus delay set to yield nearly uniform enhancement for CH, CH2 and CH3 groups. The 180° composite pulses are applied in 13C channel to overcome the inhomogeneity of B1 field and the offset effect to improve the measurement reliability. Simulated annealing optimization is further applied to achieve quantitative spectral editing of refocused INEPT. The above methods were validated using model compounds such as artemisinin and simvastatin, and the relative standard deviations of the quantitative integrals with Case I delay set were 1.6% and 3.3%, respectively. As an application of the proposed method, major fatty acid compositions in soybean oils were determined using quantitative refocused INEPT, and the results were consistent with those determined by conventional quantitative 13C NMR, while the measurement time was significantly reduced. The quantitative refocused INEPT method is particularly attractive for rapid, accurate detection of complex systems such as petroleum and polymers.

Keywords

• liquid-state nmr
• quantitative detection
• refocused inept
• simulated annealing