Multiple-site decoupling method

In most cases, ¹⁹F decoupling is not completely achieved(Fig.2) because of wide chemical shifts of ¹⁹F(Fig.1). JNM-ECA series, employing multiple sequencer system, can assign more than one RF source to a single channel. Thereby, simultaneous irradiation from several RF sources having various offsets can effectively decouple entire regions. Also, each decoupling range can be limited, and so heating problem is easily avoided(Figs.3 and 4). For example, in the case of CF₃CHFCF₂OCH₂CH₃, giving ¹⁹F signals around -80ppm and -212ppm(Fig.1), simultaneous decoupling at these regions yield a ¹³C{ ¹H,¹⁹F} spectrum where couplings with ¹⁹F are com- pletely decoupled(Fig.5).Thus, multiple-site decoupling is useful for many fluorine-containing samples, where ¹⁹F signals appear in separate regions.

Fig.1　¹⁹F{¹H} spectrum of CF₃CHFCF₂OCH₂CH₃

Fig.2　¹³C{¹H,¹⁹F(-150ppm)} spectrum of CF₃CHFCF₂OCH₂CH₃.
※¹⁹F irradiation at -150ppm does not cover the entire region and fails in complete decoupling.

Fig.3　¹⁹F double irradiation sequence.

Fig.4　Parameter setting window for ¹⁹F double irradiation.

Fig.5　¹³C{¹H,¹⁹F(‒80ppm,‒212ppm)} spectrum of CF₃CHFCF₂OCH₂CH₃

Spectrometer:JNM-ECA500