DOSY Experiments - Emory University

The number of increments to use depends on the range of diffusion coefficients to be covered
and on the balance between systematic and random errors, but will typically be in the range of 15
to 30. If significantly different diffusion coefficients are expected in a mixture more gradient
strengths might be needed to have sufficient number of usable data points also for the slowest
and the fastest diffusing component. As in any quantitative experiment, there is a balance to be
struck between signal-to-noise and accuracy when choosing a repetition rate (d1). In DOSY
experiments a delay of 1-2 T1 suffices, provided that care is taken to establish a steady state
before acquiring data. It is recommended to set ss to 8 or 16 to have steady-state pulses at
the beginning of the experiment and run the acquisition interleaved (set il='y') especially for
experiments covering several hours of experimental time.
Each sequence comes with a pulse sequence specific acquisition panel. It enables the operator
to set parameters and setup related commands directly. Figure 9 shows the acquisition panels of
the Doneshot sequence. The Acquire/Defaults panels provide access to the most important
parameters to set up the experiment. For users with low panel level this is the only acquisition
panel available. The Acquire/Pulse Sequence panel lists all relevant sequence related
parameters.
Figure 9 The Acquire/Defaults and Acquire/Pulse Sequence VnmrJ panels of the
Doneshot pulse sequence.
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