Zero-Field NMR Enhanced
by Parahydrogen in Reversible Exchange
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Abstract
We have recently demonstrated that sensitive and chemically
specific NMR spectra can be recorded in the absence of a magnetic
field using hydrogenative parahydrogen induced polarization (PHIP)− and detection with an optical atomic magnetometer. Here, we show
that non-hydrogenative parahydrogen-induced polarization− (NH-PHIP) can also dramatically enhance the sensitivity of zero-field
NMR. We demonstrate the detection of pyridine, at concentrations as
low as 6 mM in a sample volume of 250 μL, with sufficient sensitivity
to resolve all identifying spectral features, as supported by numerical
simulations. Because the NH-PHIP mechanism is nonreactive, operates
in situ, and eliminates the need for a prepolarizing magnet, its combination
with optical atomic magnetometry will greatly broaden the analytical
capabilities of zero-field and low-field NMR