States-TPPI method

The States-TPPI method does not suppress these axial peaks, but moves them to the edge of the spectrum so that they are less likely to obscure wanted peaks. All that is involved is that, each time td is incremented, both the phase of the pulse which precedes q and the receiver phase are advanced by 180° i.e. the... 

The StateS TPPI method [2.44] This method combines elements from both the States et al. and TPPI method to obtain phase sensitive spectra. 

Figure 13 Pulse sequence for the solid-state 31P—1H frequency-switched Lee-Goldburg (FSLG) experiment. Proton-proton homonuclear decoupling was performed by using the FSLG decoupling sequence. Quadrature detection in Wi was achieved by using the TPPI method. During the acquisition period, TPPM heteronuclear decoupling was applied.

X, X, X, x), 2(x, -X, -X, x). The phases tjj and < 4 were adjusted for optimum coherence transfer. While ip was constant, was inverted every eight scans. Phase 2 was incremented using the States-TPPi (Bax et al., 1991) method. (Adapted from Schmidt et al., 1993, courtesy of Academic Press.)... 

We will see that in 2D NMR, the sampling in the second dimension can also be done either way, except that this choice is up to the user and is not hard wired. The alternate ( Bruker-like ) sampling method is called TPPI (time proportional phase incrementation), and the simultaneous ( Varian-like ) method is called States or States-Haberkorn (after the originators of the technique). The consequences for processing and interpretation of the data are the same in the second dimension of 2D spectra as they are in ID NMR. 

Figure 2 Pulse sequences used in this article. All experiments can be acquired in the phase-sensitive mode, using either TPPI or the States method. Sequences 12 and 13 are best displayed in the magnitude mode because of phase modulation owing to homo-nuclear couplings in F2. All inverse correlations, except for sequences 12 and 13, can be preceded by a BIRD (bilinear rotating decoupling) pulse sandwich to allow for a fast repetition rate of scans. For simplicity gradients are not given here in most cases.

In 2D NMR, it is not possible to use a second detector in the fi dimension. There are alternatives which provide the equivalent of phase sensitive detection in the dimension two of these are the States method and time proportional phase incrementation (TPPI). 

---