Time-proportional phase incrementation TPPI

Recording and processing the two signals of Eq. 10.14, which are in quadrature, is the analog in the h dimension of the use of two phase-sensitive detectors in the t2 dimension. As we showed in Section 3.7, there is an alternative to use of two detectors. The Redfield method uses one detector but increments the receiver phase by 90°, as illustrated in Fig. 3.8. An analogous technique is available to treat tj data—time-proportional phase incrementation,TPPI.38 108... 

The Spectrum of fig. 3 demonstrates the use of the spin echo to remove inhomogeneous line broadening and the use of time proportional phase increments (TPPI) to restore the offset. Resolution is limited by truncation of the multiple quantum free induction decay and scale of reproduction. The actual linewidth is less than 2 Hz for all orders and suffices to resolve all allowed transitions of all orders. 

HIGH RESOLUTION SPECTRA BY TIME PROPORTIONAL PHASE INCREMENTS (TPPI)... 

If the phase of the excitation radiation is incremented by Atime proportional phase incrementation (TPPI), the TV-quantum spectrum is offset by a frequency NA from the transmitter in the 2D NMR spectrum. MQ orders are separated in frequency by Aco in the same fashion as if an offset had been employed. 

Make sure the correct phase sensitive type is selected as indicated in the manufacturers documentation (time proportional phase increment (TPPI)). 

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). 

Proton-proton homonuclear decoupling has been performed by the ESLG decoupling sequence [46]. Quadrature detection in coj was achieved by using the time proportional phase increment method (TPPI) [47]. During the acquisition period, two pulse phase modulation (TPPM) heteronuclear decouphng ]48] was applied (Figure 7.6). 

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. 

The idea behind the TPPI (time proportional phase incrementation) or Marion-Wuthrich (MW) method is to arrange things so that all of the peaks have positive offsets. Then, frequency discrimination would not be required as there would be no ambiguity. 

The quadrature detection mode is given as a suffix to the main sequence name me magnitude calculated, TPPI time proportional phase increment, E/A Echo / Antiecho The term "selective" is reserved exclusively for sequences using selective pulses. If selectivity is achieved using other methods this is defined using a different term. 

In the TPPI procedure, the phase (j) is made proportional to td i.e. each time td is incremented, so is the phase. We will suppose that... 

---