Multiple-site decoupling method

  • Summary


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



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