Robust NMR water signal suppression for demanding analytical applications†
We describe the design and application of robust, general-purpose water signal suppression pulse sequences well suited to chemometric work. Such pulse sequences need to deal well with pulse mis-calibrations, radiation damping, chemical exchange, and the presence of sample inhomogeneities, as well as with significant variations in sample characteristics such as pH, ionic strength, relaxation characteristics and molecular weight. Of course, such pulse sequences should produce un-distorted lineshapes and baselines and work well both under automation and in the hands of non-experts. As an example, one such pulse sequences, Robust-5, will be presented. This new pulse sequence meets those criteria and is able to reduce a 50 M proteo water signal down to a 0.9 mM level, without fine tuning, and under automation, and it is therefore well suited to the most demanding of analytical applications.