美国药典看到这句话: For each sample, an initial short spectrum is collected (1scan), and the water resonance is then suppressed by selective irradiation during the relaxation delay. Final Analysis: Proceed as directed in the chapter. spectra are recorded over 32 scans. 求助NMR大神,USP里面这句话怎么理解? selective irradiation during the relaxation delay.对应的水峰压制程序有哪些? 谢谢