Processing of 2D NMR Data

The basic processing steps for ID NMR data can also be applied to the processing of 2D NMR data with similar effects. Of particular importance for the processing of 2D data matrices are zero filling and apodization. Usually 2D experiments are recorded with a relatively small number of time domain data points TD2, compared with a ID experiment, and small number of increments TDl in order to minimize data acquisition times. Typical time domain values are 512, Ik or 2k words. Small values of TD2 and TDl and the correspondingly short acquisition times cause poor spectral resolution and 

Data decomposition is not a common part of 2D data processing, but in the course of evaluating a pulse sequence the comparison of the same row or column which belong to different data sets can be very helpful. Similarly if a kinetic experiment has been performed as a pseudo 2D experiment it is easy to process the data to determine the rate constants if the data is treated as a set of ID spectra. 

In Check it 3.3.2J the IH magnitude COSY spectrum of a ternary mixture of diethylether (1.0 (molar ratio)), ethyl bromide (0.2) and ethylmagnesium bromide (0.15) is simulated to demonstrate the importance of choosing the correct apodization parameters, particularly in a sample with a wide range of signal intensities. 

In a similar manner to ID data, the Fourier transformation used for 2D data can be treated as a blackbox function but with the additional consideration of the quadrature detection mode used in the second dimension. This aspect has already been discussed in section 2.3.1 and the reader is referred to this chapter for further details on the data processing and selection. 

In 2D WIN-NMR the Fourier transformation of 2D raw data is accomplished in one step using the xfb command or stepwise using the xf2 and then the xfl command. In either case the processing parameters including the selection of the appropriate FT mode must be set in the General parameter setup dialog box prior to the Fourier transformation. 

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Processing of ID NMR Data HELP Routine Processing of 2D NMR Data HELP Routine... 

The second part of this section examines the processing of 2D NMR data using 2D WIN-NMR. By necessity the description of 2D data processing is very brief and the raw 2D data is processed in a single step rather than the stepwise approach used for ID data. Table 3.5 at the end of this section summarizes the recommended processing parameters for a number of the more common 2D experiments. 

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