From the environment to NMR: water suppression for whole samples in their native state
Hussain Masoom A , Antonio Adamo A and André J. Simpson A BA Department of Chemistry, University of Toronto – Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada.
B Corresponding author. Email: andre.simpson@utoronto.ca
Environmental Chemistry 13(4) 767-775 https://doi.org/10.1071/EN15139
Submitted: 3 July 2015 Accepted: 16 December 2015 Published: 23 March 2016
Environmental context. Environmental samples are best analysed in their native state, with minimal sample preparation, to fully understand the complex interactions and processes occurring in environmental systems. Nuclear magnetic resonance spectroscopy is a powerful tool used to study environmental samples but sample pre-treatment is often required to remove water and improve analysis. We introduce an experimental approach to remove water signals from environmental samples in their natural state, which opens the door to intact sample analysis and more environmentally relevant science.
Abstract. Studying environmental samples in their natural state is critical as drying, fractionating or extractions can alter the composition, structure, conformation and biological activity, as well as perturb essential interfaces and domains. Nuclear magnetic resonance (NMR) spectroscopy is a powerful and versatile tool that provides unprecedented levels of information regarding structure and interactions. Both high-resolution magic-angle-spinning and comprehensive-multiphase NMR probes facilitate the study of natural multiphase samples. 1H NMR spectroscopy is the most sensitive and provides unique information on swollen components and interfaces. However, samples such as plants, organisms and soil have a high aqueous content and a range of free, exchanging and bound water, leading to a broad and intense water signal that can span the entire 1H spectral region masking information from other components. In this manuscript, a water suppression approach termed Tailored Water suppression for Inhomogeneous Natural Samples (TWINS) is developed out of a practical need to study samples in their native state. TWINS builds upon the most effective approach to date (SPR-W5-WATERGATE) for natural samples with the addition of various elements to make the approach effective in the most challenging systems. TWINS was demonstrated on a range of environmental samples in both 1-D and 2-D NMR experiments. A lock capillary was developed to separate the lock solvent from the sample, further reducing sample alteration. In summary the more challenging the sample, the more TWINS outperformed conventional approaches. In turn this increases the range and diversity of samples that can be studied in their natural state critical for a wide variety of fields and applications.
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