Continuous flow high field nuclear magnetic resonance detector for liquid chromatographic analysis of fuel samples

The design and characterization of a continuous flow probe insert for a 200-MHz 1H nuclear magnetic resonance (NMR) detector for high-performance liquid chromatography (HPLC) are described. Modern superconducting magnet based systems present different requirements for flow probe design, but a considerable improvement over older spectrometers is readily achieved. Improvements in both spectroscopic and chromatographic resolution are shown to enhance the analytical utility of LC-1H NMR. Spectral resolution is 2 Hz or 4 Hz with optimum sensitivity. Injection volumes of 10 to 25 μL provide detection limits of 10 μg. The LC-1H NMR analyses of a model mixture and two experimental petroleum based fuel samples are presented. A LC-1H NMR based method for calculating the average degree of substitution of aromatic ring systems is discussed in detail