600 MHz Static 19F—1H Low-E Probe

Purpose

This static solid state instrument is a variation of cross-coil low-E design, built specifically for the ¹⁹F—¹H CPMG or similar multi-pulse applications in dilute and heat-sensitive samples. In ¹⁹F—¹H experiments, high-frequency irradiation on both channels can contribute to sample heating. This is particularly important for CPMG or related multi-pulse experiments, where duty cycles of ¹⁹F and ¹H irradiation are of comparable magnitude. Also, since the Larmor frequencies of ¹⁹F and ¹H are only 6% apart, achieving good isolation of a ¹⁹F detection channel from ¹H decoupler noise is another common challenge for ¹⁹F—¹H probes. Some probes utilize a single port for both channels, and then employ an outside splitter and filters. This probe instead uses two nested low-E resonators (LGR's) to reduce heating at both frequencies. The low mutual inductance of the orthogonal low-E approach has been used to develop a ¹⁹F—¹H probe for 600 MHz that provides 24 dB of isolation within the probe itself and >80 dB with external filter. Flat coil aperture accepts 7.5x5.5mm rectangular glass cells with mechanically oriented samples, similar to those used in our PISEMA probes. This probe is available for Magnet Lab users. An example 2D ¹⁹F CPMG spectrum is shown in Fig. 1, courtesy of Dr. Raiker Witter. Interested spectroscopists should contact Peter Gor'kov to make arrangements to use this probe.

Sample supplies for flat coil

Fig. 1.  2D 19F-CPMG spectra of Flufenamic acid in DMPC bilayers (1:8 molar ratio, fully hydrated, 35°C) at 600 MHz. 256 t1 increments with 16 transitions, 19F B1 = 100 kHz, 1H B1 (de­coupling) = 70 kHz. Spectrum courtesy of Dr. R. Witter.