Recent advances in magnet designs combined with efficient shimming techniques of magnetic fields have led to permanent magnets as alternative sources to superconducting ones for the magnetic field generation in compact NMR instruments. These devices present a weaker magnetic field intensity but still maintain access to chemical shift information. In the last years, these important features have boosted the application of bench-top Low-Field NMR devices as an alternative method of analysis to the vibrational ones for monitoring process activities. Majorly, LF-NMR devices are applied combined to chemometric methods of analysis, where Partial Least Squares Regression (PLS) is the most used.<br/>Using a PLS calibration model to predict any sample property requires the development of a new calibration model, specific for the sample property in study and to the applied instrument. The calibration step is the most laborious task during the application of PLS method, once it needs a considerable number of representative calibration samples, and their spectra, to build a robust calibration model. After that, the PLS calibration model could be strictly applied to the same kind of calibration samples at same experimental and instrumental conditions.<br/>In this way, to overcome the instrumental limitations and broadening the application of a built PLS calibration model to other LF-NMR devices (with same or different magnetic field than the used to build the calibration model), this study investigated the use of Double Window Piecewise Direct Standardization (DW-PDS) method to enable the calibration transfer between LF-NMR instruments.<br/>When applied on automotive gasoline samples to predict distillation recovery temperature, specific gravity and final distillation point, the calibration transfer with DW-PDS enabled the successfully application of a PLS calibration model developed on a 60 MHz instrument (primary instrument) with 145 calibration samples to other 3 instruments: 43 MHz, 80 MHz and a new 60 MHz device. It was possible using less than 8 transfer samples. As far as we know this is the first time that calibration transfer was applied to LF-NMR devices.<br/>

Calibration transfer between low-field NMR instruments

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.