Broadband ¹⁹F TOCSY using BURBOP-based spin lock.

Area of Science:

• Nuclear Magnetic Resonance Spectroscopy
• Physical Chemistry
• Organic Chemistry

Background:

• Total Correlation Spectroscopy (TOCSY) is crucial for molecular structure elucidation.
• Observing ¹⁹F NMR correlations typically requires specialized techniques due to wide spectral windows.
• Previous spin lock methods like DIPSI-2 have limitations in spectral width and RF field strength.

Purpose of the Study:

• To introduce and validate a new spin lock method using BURBOP universal rotation pulses for ¹⁹F NMR TOCSY.
• To assess the performance of the BURBOP spin lock in terms of RF field strength, spectral window, and duty cycle.
• To demonstrate the applicability of this method for analyzing complex mixtures, such as perfluorocarbons.

Main Methods:

• Implementation of a BURBOP pulse train for generating a robust spin lock.
• Acquisition of ¹⁹F NMR TOCSY spectra over a 46 kHz spectral window (122 ppm at 9.4 T).
• Comparison of BURBOP spin lock parameters (RF field strength, duration, duty cycle) with existing methods.

Main Results:

• Successful generation of a spin lock sufficient for TOCSY over a 46 kHz ¹⁹F spectral window.
• The BURBOP spin lock required a lower RF field (γB₁ = 15 kHz) compared to DIPSI-2.
• The method was applied effectively to obtain spectral separation and full correlations for a mixture of perfluorocarbons without damaging the RF coil.

Conclusions:

• BURBOP-based spin locks offer a more efficient and versatile approach for ¹⁹F NMR TOCSY.
• This technique allows for broader spectral coverage and lower RF power, enhancing NMR analysis capabilities.
• The method is suitable for detailed analysis of complex fluorinated compounds.