OneNMR Probe 400-700 MHz
Technical Overview
Introduction
The OneNMR probe represents a new class of NMR probes. This technology is
the most signifi cant advance in solution-state probe technology in over a decade.
The OneNMR probe is not a reworked version of a broadband or indirect detection
probe, but a new technology free of the performance trade-offs of those classic
designs. It is see an entirely new design with performance benefi ts unmatched by
other probes.
Sensitivity
The OneNMR probe is simultaneously
optimized for both high- and
low-band frequencies, and delivers
the performance advantages of
both the classic carbon probe and
the highly sensitive proton probe in
a single design. The signal/noise
(S/N) specifi cations for the family of
400-700MHz OneNMR probes is shown
in Table1, with excellent sensitivity on
both channels.
It is understood that actual S/N
performance will vary depending on
how well your system is shimmed.
The design and manufacturing of the
OneNMR probe results in a very tight
performance distribution so that all
probes are very similar. The S/N results
in Figure 2 were obtained using a
typical 400 MHz OneNMR probe with
an Agilent 400-MR magnet.
The proton sensitivity data in Figure 1
is 20 % greater than the specifi cation.
These data illustrate one of the dangers
of comparing probes on the basis of
published specifi cations alone. Probe
specifi cations for a given vendor (probe
to probe) tend to be consistent, making
direct within-vendor comparisons easy.
However, direct comparisons between
vendors are much more diffi cult
owing to differences in methods and
philosophy. When sensitivity is used as
a basis for probe selection, your safest
bet is a direct head-to-head comparison
with the same sample (yours) and
operator (you).
Table 1. 400 -700 MHz OneNMR Probe Sensitivity Specifi cations.
400 500 600 700 Sample Tube
1
H 480:1 730:1 900:1 1150:1 0.1 % Ethybenzene Wilmad 545-pp
13
C 225:1 300:1 380:1 460:1 0.1 % Ethybenzene Wilmad 545-pp
15
N 20:1 25:1 35:1 45:1 90 % Formamide Wilmad 535-pp
31
P 90:1 135:1 170:1 220:1 0.0485 M TPP Wilmad 535-pp
19
F 550:1 800:1 1050:1 0.05 % TFT Wilmad 535-pp
A
C
Figure 1. 400 MHz OneNMR Probe High & Low Band Sensitivity (A) Proton S/N, (B) Fluorine S/N,
(C) Carbon S/N.
B
2
The OneNMR Probe lock sensitivity
is also enhanced to provide a more
stable lock and to support fast gradient
shimming for increased fl exibility (e.g.
3mm tubes) and greater ease-of-use.
Sensitivity, while important, is just
one aspect of probe performance and
only part of the story. The sections
which follow will introduce you to the
advantages of the OneNMR probe that
extend far beyond sensitivity alone.
Pulse Performance and
Lineshape
The 400-700 MHz OneNMR Probes
provide superior lineshape both
spinning and non-spinning which means
ease of shimming and well resolved
spectra. The lineshape specifi cations
are shown in Figure 2, along with an
example of the proton-decoupled 13C
NMR spectrum of dioxane.
400-700 MHz OneNMR Probe
Lineshape Specifi cations
Spinning Non-spin
13C1
50 % ≤ 0.15 0.45 0.8
0.55 % ≤ 1.5 5.0 7.0
0.11 % ≤ 3.0 10.0 14.0
Sidebands ≤ 1 % 1 %
Figure 2. OneNMR Probe lineshape specifi cations (left) and a spinning 13C dioxane example.
Table 2. 400-700 OneNMR Probes pulse performance.
PW90 400 Mhz 500 MHz 600 MHz 700 Mhz Sample
1
H 7 µsec 8 µsec 9 µsec 10 µsec 1 % 13C-Iodomethane
13
C 8 µsec 10 µsec 9 µsec 10 µsec 1 % 13C-Iodomethane
15
N 14 µsec 20 µsec 18 µsec 20 µsec 90 % Formamide
31
P 8 µsec 15 µsec 12 µsec 15 µsec 0.0485 M TPP
19
F 8 µsec 10 µsec 10 µsec 0.05 % TFT
1
H
H
13
C Lineshape
Decoupled Dioxane
0.08 50 %
0.67 0.55 %
1.40 0.11 %
The OneNMR probe’s modern design
and effi cient power handling leads to
excellent pulse performance. The PW90
pulse widths for the 400-700 MHz
OneNMR probes are listed in Table2.
These relatively short PW90’s are ideal
for experiments requiring excitation
or decoupling over a wide spectral
window (e.g. 19F).
3
RF Hom ogeneity
The OneNMR probe has excellent RF
homogeneity on both channels while
a dual broadband (DB) probe has
relatively poor RF homogeneity. If you
look at a spin projection comparing
a standard dual broadband probe
(CoilA) to the OneNMR Probe (CoilB),
as shown in Figure 3, you can see
that over the length of the sample,
the amplitude of the signal with the
OneNMR Probe is more uniform than
for the standard dual broadband probe.
What this means is that only the
spins in the center of Coil A will be at
maximum amplitude while nearly all
the spins of Coil B will be at maximum
amplitude. For a single pulse this
difference may not be so important,
but many experiments have several
pulses in rapid succession. So if on
the fi rst pulse only 85% of the spins
line up, then on the second pulse only
85% of 85% line up, and so on until
you very rapidly lose your signal. In
contrast, with a more homogenous
RF fi eld, you lose less signal with each
pulse and the summed signal from
CoilB ends up being larger than CoilA.
This is especially important when you
consider that modern pulse sequences
tend to incorporate more rather than
fewer pulses.
The standard way to look at this is
by comparing the 1H 810°/90° or
the 13C 720°/0°, where the higher
ratio of intensities indicates better RF
homogeneity. An average 810°/90° for
an indirect detection probe is around
70% whereas a standard DB probe
will give you around 55 %. When we
initially introduced the OneNMR Probe,
both the 810°/90° and the 720°/0°
were 78%, and the current release is
even better. Consequently, not only is
Coil A =
Coil B =
Figure 3. A comparison of spin projections (signal intensity along the z-axis of the coil) of a
standard DB probe (Coil A , in red) and the OneNMR Probe (Coil B, in blue). The OneNMR Probe
provides a more uniform signal than the standard DB probe.
Figure 4. Relative per formance of the OneNMR Probe compared to the standard DB probe.
The results are given in units of time to complete the experiment.
the performance of the OneNMR Probe
better than a standard DB probe in a 1D
experiment, it is signifi cantly better for
2D experiments as well.
Probe – 20% better for a single 90°
pulse. However the RF homogeneity
(810°/90°) of the OneNMR probe
is better than the indirect detection
probe by about 9%. This seemingly
The advantages of good RF
homogeneity can be seen by comparing
the OneNMR Probe to an indirect
detection probe. The proton coil of the
ID probe is closer to the sample and, as
you would expect, this gives it a better
signal-to-noise than the OneNMR
small difference in RF homogeneity
has a big impact in 2D experiments
with multiple pulses, such as the
gHSQC-NOESY (Figure4). The more
homogenous RF fi eld of the OneNMR
probe compensates for the lower
signal-to-noise ratio. This effect is
4
shown in Figure 5, where the OneNMR
Probe (middle) performs almost as well
as the indirect detection probe (right)
in this 2D experiment. For comparison,
the performance of a DB probe (left) is
also shown.
Superior Decoupling
When you combine the effi cient power
handling, pulse performance, and RF
homogeneity of the OneNMR probe,
the result is outstanding decoupling
performance. In real-world applications,
like a 13C observe experiment, improved
decoupling results in narrower lines
(increased resolution) and increased
sensitivity. The improved decoupling
can be seen by comparing the linewidths of the OneNMR and Dual
Broadband probes under identical
conditions (see Figure 6).
Superior decoupling leads directly to
increased sensitivity. The 500 MHz 1D
carbon spectra for vitamin B12 were
measured under identical conditions
using the ID, DB, and OneNMR probes.
The results (Figure 7) show signifi cant
sensitivity enhancements for many
peaks when using the OneNMR
probes. You would not have predicted
this outcome on the basis of carbon
sensitivity alone, since the Dual
Broadband has a slight advantage.
Once again we see that sensitivity,
while important, isn’t the whole story.
Figure 5. OneNMR Probe advantage in 2D experiments. Three gHSQC-NOESY spectra are identically
scaled using the AutoX DB Probe (left), the OneNMR Probe (middle), and the AutoX ID Probe
(right). The superior RF homogeneity of the OneNMR probe compensates for the ID probe’s greater
sensitivity (20%) to yield comparable results.
Figure 6. Decoupled Cholester yl Acetate (28 ppm) resonance at 400 MHz, comparing the 20% linewidth of the (a) OneNMR Probe and (b) Dual Broadband Probe.
Because decoupling effi ciency is such
an important factor in 13C performance,
it is desirable to include it in any
sensitivity testing. For this reason,
we fi nd 10% ethylbenzene a superior
(real-world) 13C sensitivity test since it
is measured under proton-decoupled
conditions. The ASTM standard,
while important for its historical
signifi cance, was developed for use
when decoupling effi ciency was poor.
Since modern NMR spectrometers
exhibit excellent decoupling, the ASTM
standard is no longer relevant.
Figure 7. Decoupled 5 00 MHz 1D Carbon spectra for vitamin B12 collected using an ID probe(top),
DB probe (middle) and OneNMR probe (bottom).
5
Water Suppression
The OneNMR probe’s excellent
sensitivity, pulse performance, and RF
homogeneity make it an ideal probe
for water suppression. The 400 MHz
presaturation spectrum of 2 mM
sucrose (90:10 H2O/D2O) shows a 65Hz
residual water peak and an anomeric
splitting of 85% (Figure 8). The righthand spectrum was acquired under
automation using PURGE and 8 scans.
These results show that the OneNMR
probe has outstanding performance in
water suppression.
A B C
Figure 8. 2mM sucrose (90:10 H2O/D2O) at 400 MHz: presaturation water suppression (A), anomeric
split ting (B), and PURGE (C)water suppression, acquired under automation.
Salt Tolerance
NMR samples interact
electromagnetically with the RF coils
in the NMR probe. The magnitude of
this interaction is proportional to the
dielectric constant of the sample. When
placed in the probe, samples with a
high dielectric constant (e.g., ionic
solutions) couple strongly to the RF
coils, increasing the capacitance of the
circuit and changing the tuning of the
probe. Unless the probe is re-tuned for
this new condition, the length of the
90°pulse width can suffer dramatically.
Conversely, a probe tuned appropriately
for a high dielectric sample will not
perform as well if the sample has a
comparatively low dielectric constant
(e.g., chloroform).
The performance cost for running
the NMR system in a poorly tuned
state is signifi cant for most standard
probes, but this is not the case for the
OneNMR Probe. The unique design
of the OneNMR probe is very tolerant
of dielectric differences, thereby
eliminating the need for sample
tuning for routine 1H and 13C studies.
A
Tuned to chloroform 10.75 µs 1.00
Tuned to 200 mM salt 15.00 µs 0.59
Figure 9. Relative
200mM salt for the (A) 500 MHz Dual Broadband Probe, and the (B) 500 MHz OneNMR Probe. Both
signal-to-noise measurement s were made using the pulse width and power levels calibrated for the
accurately tuned sample.
13
This feature allows high-quality data
collection on typical organic chemistry
samples without the cost in time, wear
and tear, and complexity required to
actively tune the probe for each sample.
Dual Broadband
PW90 S/N
C probe performance for a chloroform sample when tuned to chloroform and
B
Tuned to chloroform 6.95 µs 1.00
Tuned to 200 mM salt 7.55 µs 0.94
conditions. Repeating the experiment
with the OneNMR probe shows it to
be remarkably tolerant of these high
salt conditions retaining 94% of its
sensitivity with a much smaller impact
OneNMR
PW90 S/N
on pulse width.
To demonstrate this effect, a
standard 500 MHz, 5 mm DB probe
was accurately tuned on an organic
chemistry sample dissolved in
deuterochloroform. Carbon spectra
were acquired to establish baseline
performance for the 90° pulse width
and sensitivity. An aqueous 200 mM
NaCl sample was then inserted into
the probe and the system was tuned
to this sample. Using this tune setting,
the chloroform sample was returned
to the magnet, and the pulse width
and sensitivity data were once again
collected. The results (Figure 9) show
that a classic DB probe suffers a
signifi cant loss in sensitivity (39%)
Given the 13C performance results
presented above and the excellent 1H
specifi cations of the OneNMR probe,
one might anticipate that the proton
channel would suffer from this type
of intentionally mis-optimized tune
experiment. This is not the case. When
the same worst-case set of tuning
experiments were repeated using the
high frequency channel on the 500MHz
OneNMR probe, the performance
changes between the well-tuned
probe and the poorly tuned probe were
negligible. The proton 90° pulse width
increased by 5.9%, while the S/N ratio
decreased by only 5.3%.
and pulse performance under these
6
The HSQC experiment is a cornerstone
NMR experiment for organic chemistry.
It is also one of the more challenging
experiments with respect to the quality
of the NMR pulses used to collect
the data. This makes it a perfect test
experiment to demonstrate the ability of
the OneNMR probe to yield high-quality
data without the need for careful
tuning adjustments.
Figure 10 displays two gHSQC data sets
obtained on a mixture of two alkaloids
in deuterochloroform using the
500MHz OneNMR probe. These data
show that running a demanding 2D
experiment without tune optimization
has little effect on sensitivity. In fact,
comparison of the fi rst increment of
two adiabatic HSQC experiments with
the probe tuned, versus detuned as
described above, yielded a S/N change
of less than 9%.
Solvent Tuning Tolerance
Figure 10. gHSQC data spectra acquired on a mixture of two alkaloids in deuterochloroform using
the OneNMR probe. The data in the left panel were obtained with the RF coils carefully tuned to the
sample. The data in the right panel were obtained on the same sample but with both the proton and
carbon RF coils tuned on a sample of 200 mM NaCl in D2O. No attempt was made to compensate
for the mis-optimization of the RF pulses in the second experiment; the pulse widths, power levels,
and parameterization used for each experiment were identical, and displayed at the same absolute
contour level. T he experiment time for each data set was less than 5 minutes.
The ability of the OneNMR probe to
accept a wide range of solvents with
minimal change in probe tuning means
that, for routine organic chemistry
applications, the OneNMR probe can
be used to collect high-quality data
without adjusting the tuning circuit
from sample-to-sample.
The typical NMR solvents used in
organic chemistry do not represent a
large range of dielectric constants:
benzene (ε0 2.27) is at the low end of
the scale and water (ε0 80.1) is at the
high end. Given this situation, one
could easily tune the OneNMR probe to
the middle of your working range and
simply leave it there. The full range of
organic NMR solvents would then be
available for use without any need to
retune the probe, while maintaining
essentially all of the excellent
performance of the OneNMR probe.
This is especially useful for high
throughput applications.
Automatic Probe Tuning –
ProTune
ProTune is an advanced system for
automatic probe tuning and matching
which includes accessory hardware and
software components built into Agilent
VnmrJ software.
ProbeID
ProbeID is a new feature which allows
the console and software to recognize
and communicate directly with the
probe. Building this intelligence into the
probe allows you to work more
intuitively while the system does the
heavy lifting. Benefi ts of ProbeID
include ensuring that various
operational parameters remain within
the limits of the probe (such as RF
power and temperature). The software
can prevent the accidental selection of
incompatible probe fi les, which can
be helpful in automation and multi-
user environments.
ProbeID allows the factory to store
probe specifi cations, calibrations, and
probe-test data directly on the probe
itself. The probe will contain a copy of
the factory and installation test data,
tuning data, and probe fi les should they
ever be needed for reference or service.
With ProbeID, probe-specifi c data
always remains with the probe.
7
Summary
The OneNMR probe represents an
entirely new class of NMR probes,
unlike the classic broadband or indirect
detection probes available today.
The OneNMR probe has excellent
sensitivity on both channels, but this
is just a small part of the performance
capabilities. The probe exhibits
excellent RF-homogeneity on both
channels, excellent lineshape and pulse
performance, superior decoupling,
enhanced lock sensitivity, and
unprecedented salt and solvent tuning
tolerance. The performance benefi ts of
the OneNMR probe are unmatched by
any other probe.
Learn more
www.agilent.com/chem/nmr
Find a local Agilent customer center
www.agilent.com/chem/
contactus
USA and Canada
1-800-227-9770
agilent_inquiries@agilent.com
Europe
info_agilent@agilent.com
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This information is subject to change
without notice.
© Agilent Technologies, Inc., 20 12
Printed in the U SA, March 30, 2012
5990-7612EN
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