Rapid, Quantitative Nuclear Magnetic Resonance Test for Oxygen-17 Enrichment in Water

Nuclear magnetic resonance (NMR) studies involving O-17 are increasingly important in molecular biology, material science, and other disciplines. A large number of these studies employ (H2O)-O-17 as a source of O-17, and this reliance can be limiting because the high cost of (H2O)-O-17. To overcome this constraint, a recent study proposed a distillation scheme capable of producing significant quantities of (H2O)-O-17 at a low cost. Although this method is reported to be effective, the reactions proposed to quantify percent of O-17 enrichment are either time intensive or have a risk of errors due to the isotope effect. Here, an alternative reaction scheme is described to measure O-17 water that ultimately creates methyl benzoate as the sole O-17-containing product. The proposed reaction is completed in a matter of minutes at room temperature, produces only one O-17 product, and requires no cleanup step. The large isotope shift observed in solution NMR between the C-13 = O-16 and C-13 = O-17 resonances allows for integration of the individual peaks. This C-13 NMR analysis is found to be highly accurate over a wide enrichment range and is accessible to most NMR spectroscopists.