DOSY Experiments - Emory University

Probespinmax 3000 / 10000*
(* mas and 10000 1/s will be the options for the newly released FastNano TM probe)
corresponding to VnmrJ parameters probetype, spintype, and spinmax. The first one,
probetype, is a new global parameter. While the addprobe macro adds this new parameter to
the probe file (with a default value of liquids), the updateprobe macro will add that definition to
an existing probe file if it is not present yet. Alternatively, an existing probe file may be edited,
adding the first of these three lines exactly as shown above. The other two parameters,
spintype and spinmax, do exist since VnmrJ 2.2C and are only relevant for systems with
software spin control. Upon changing to a Nano Probe, all three parameters are activated (via the
_probe macro) and the system is ready to do the extra, Nano Probe related tasks automatically.
2.3.1 User created DOSY pulse sequences
This software setup requires a few changes to existing pulse sequences: the actual gradient
adjustment takes place within the pulse sequence itself, i.e., is performed at “go” time (through
the "Acquire" button or the cpgo macro). It is therefore the pulse sequence programmers privilege
and responsibility to ensure that the pulse sequence is Nano Probe compliant.
All DOSY pulse sequences in VnmrJ3.0 have been adjusted to be compliant with Nano Probes. A
user created diffusion pulse sequence could be made Nano Probe compatible by following the
steps listed below:
1. Be sure that the probe file has all relevant parameters defined and set, as outlined above.
Include the necessary changes in your pulse sequence code as described below and
recompile the pulse sequence.
2. Making an existing gradient pulse sequence compatible with Nano Probes involves
several changes in the pulse sequence code itself:
Near the top of the pulse sequence, just below the line
#include
an extra include line must be added for the header file chempack.h:
#include
Define which parameter(s) need adjustment by inserting expression "A" (or "A" and "B"
together) from below. Note that a homospoil gradient pulse (i.e., a gradient that simply
destroys residual transverse magnetization) does not need this type of adjustment. Let's
assume that the relevant gradient pulse has duration of gtE and amplitude of gzlvlE. In
this case, expression "A"
gtE = syncGradTime("gtE","gzlvlE",1.0) trims the gradient pulse length
gtE and leaves the amplitude gzlvlE unchanged. Each Nano Probe compatible
pulse sequence must contain at least this definition. The third argument is a multiplier
that is typically set to 1.0 in sequences with single gradient pulse duration. If a pulse
sequence uses gradient pulses with lengths of both gtE and gtE/2 (as many
heteronuclear Chempack-type sequences), then the multiplier must be set to 0.5 to
ensure that the requirements are also met for gtE/2.
A second expression "B"
gzlvlE = syncGradLvl("gtE","gzlvlE",1.0)
used with a combination with expression "A" above adjusts also the gradient
amplitude (gzlvlE in this example) such that the gradient area (i.e., the product
gtE*gzlvlE) remains constant.
10