Practical Aspects of the Analysis of Low- and High-Field NMR Data from Environmental Samples

NMR has considerable advantages for investigation of environmental samples including the ability to measure solid-, gel-, and solution-state samples using both high-field superconducting magnets and low-field permanent magnets. Samples from diverse geochemical environments and microbial, plant, and animal systems can be analyzed using common protocols and the NMR analytical platform. To handle broad range of spectra from solid-state NMR or low-field benchtop NMR, two preprocessing tools have been developed and evaluated in my laboratory: one, SENSI, which enhances the signal-to-noise ratio by spectral integration, and the other, PKSP, which separates overlapping peaks using algorithms, such as non-negative sparse coding. In addition, the SpinLIMS database stores numerous standard spectra for molecular species ranging from small molecules to macromolecules in solid and solution states (dissolved in polar/nonpolar solvents). The database can be searched under various conditions using the InterAnalysis molecular assignment tool, which improves the accuracy of molecular assignments by integrated analysis of 2D ¹H-¹³C correlation peaks, and ¹H-J resolved peaks of small molecules dissolved in solvents such as D₂O, MeOD, and DMSO-d₆. With emphasis on the above, the current chapter provides practical aspects of the analysis of data from diverse environmental samples obtained using low- and high-field NMR instruments.