Multi-FID Detected 2D NMR

Abstract

This chapter will describe various approaches to fast 2D NMR data acquisition through the use of multi-FID detection schemes. These provide routes to time-efficient data collection often with improved sensitivity per unit time through the recording of multiple data sets within a single experiment. These include methods that employ detection of a single nuclear species as required on single-receiver instruments, as well as those that exploit the more recent multi-receiver instrument architectures that enable the direct acquisition of responses from two or more nuclear species in one experiment. We introduce general strategies for multi-FID detection, namely sequential, simultaneous (parallel), and interleaved acquisition. These are illustrated using time-shared schemes and those that utilise sequential FID detection to exploit a single magnetisation reservoir multiple times. Next, the modular NOAH (NMR by ordered acquisition using 1H detection) experiments are described which aim to exploit different, isotope-dependent 1H magnetisation reservoirs within a molecule to record multiple 2D spectra in one experiment. Finally, the use of multiple receivers in heteronuclear correlation experiments is described. The crafted combination of multiple NMR techniques into a single experiment leads to the general concept of NMR supersequences as a class of fast 2D methods.