States-TPPI
From NMR Wiki
States-TPPI technique achieves two effects for a given indirect dimension (say, dimension F1): (1) signal frequency discrimination and (2) displacement of the unmodulated artefact signal from the inconvenient location in the middle of spectrum to the edge.
(1) is achieved by recording two data sets at each t1 point - with orthogonal phases of the preparation pulse - and storing them in a separate memory location. These two measurements yield one complex data point.
(2) - by inverting phase of the preparation pulse and the receiver each time when t1 is incremented. The result of this is that the artefact signal at F1=0 Hz appears at F1=±SW/2 Hz
For example to get two sequential complex data points - on at the evolution delay t1 and the next one at evolution delay t1 + 1/SW four fid's are recoreded:
| complex point # | fid# | phase of prep. pulse | receiver phase |
| 1 | 1 | 0 | 0 |
| 2 | 90 | 0 | |
| 2 | 3 | 180 | 180 |
| 4 | 270 | 180 |
The data is subsequently processed by the complex Fourier transformation.
Reference
Marion, D., Ikura, M., Tschudin, R., Bax, A.. Rapid recording of 2D NMR spectra without phase cycling. Application to the study of hydrogen exchange in proteins
