DOSY Experiments - Emory University

gzlvlhs gradient level for sspul
hsgt gradient duration for sspul
probe_ stores the probe name used to acquire the dosy experiment
Processing Parameters:
determines the number of components to be used in fitting the
ncomp
signal decay in DOSY when dosyproc='discrete'.
nugflag
nugcal_[1-5]
dosyproc
dosybypoints
'n' uses simple mono- or multi-exponential fitting to estimate
diffusion coefficients
'y' uses a modified Stejskal-Tanner equation in which the exponent
is replaced by a power series.
a 5-membered parameter array summarizing the results of the
calibration of non-uniform field gradients. Used if nugflag='y',
requires a preliminary NUG-calibration by the Doneshot_nugmap
sequence. The values are taken from the probe file at the time of
the data acquisition
'discrete' - invokes monoexponential fitting with dosyfit if ncomp=1,
and multiexponential fitting with the external programme SPLMOD
if ncomp>1.
'continuous' invokes processing with the external programme
CONTIN and gives a continuous distribution in the diffusion
domain.
'n' divides the spectrum into individual peaks, creating one crosspeak
for each individual peak found in the 1D spectrum
'y' performs a diffusion fit for every point in the displayed region of
the spectrum that lies above the selected threshold.
4.4.2 Comparison of diffusion results obtained with and without
convection compensation
This chapter compares experimental results of an aqueous solution of a mixture of nicotinic acid
amide and amikacin (see Figure 12 for the structural formulas). The diffusion experiments were
performed without (sequence: Dbppste) and with convection compensation (sequence:
Dbppste_cc) at two different temperatures: 30 °C and 60 °C, respectively, in a 5 mm sample
tube. One may think that this sample in not particularly challenging because the components
differ significantly in size (or molecular weight) and there is no signal overlap between the
aromatic and the sugar protons in the 500 MHz spectrum of the mixture. Both components,
however, contain numerous proton lines (remember the DOSY analysis handles multiplet
components individually) and therefore the sample is particularly suitable to provide information
about the accuracy of the diffusion data.
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