ASTM E386-90(2011)
(Practice)Standard Practice for Data Presentation Relating to High-Resolution Nuclear Magnetic Resonance (NMR) Spectroscopy (Withdrawn 2015)
Standard Practice for Data Presentation Relating to High-Resolution Nuclear Magnetic Resonance (NMR) Spectroscopy (Withdrawn 2015)
ABSTRACT
This practice elaborates on the different types, definition of basic operational terms, conventions, referencing procedures and substances, and terms and recommended means for signal-to-noise ratio determination and data presentation in the area of high-resolution nuclear magnetic resonance (NMR) spectroscopy. Some of the basic definitions apply to wide-line NMR or to NMR of metals, but this practice is generally not intended to cover these latter areas of NMR. Also, this version does not include definitions pertaining to double resonance, nor to rotating frame experiments.
SCOPE
1.1 This standard contains definitions of basic terms, conventions, and recommended practices for data presentation in the area of high-resolution resolution nuclear magnetic resonance (NMR) spectroscopy. Some of the basic definitions apply to wide-line NMR or to NMR of metals, but in general it is not intended to cover these latter areas of NMR in this standard. This version does not include definitions pertaining to double resonance nor to rotating frame experiments.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
WITHDRAWN RATIONALE
This standard contains definitions of basic terms, conventions, and recommended practices for data presentation in the area of high-resolution resolution nuclear magnetic resonance (NMR) spectroscopy. Some of the basic definitions apply to wide-line NMR or to NMR of metals, but in general it is not intended to cover these latter areas of NMR in this standard. This version does not include definitions pertaining to double resonance nor to rotating frame experiments.
Formerly under the jurisdiction of Committee E13 on Molecular Spectroscopy and Separation Science, this practice was withdrawn in September 2015 and replaced by Practice E2977 for Measuring and Reporting Performance of Fourier-Transform Nuclear Magnetic Resonance (FT-NMR) Spectrometers for Liquid Samples.1
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E386 − 90(Reapproved 2011)
Standard Practice for
Data Presentation Relating to High-Resolution Nuclear
Magnetic Resonance (NMR) Spectroscopy
This standard is issued under the fixed designation E386; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope magnetic field at which the system operates is called H (Note
o
1)anditsrecommendedunitofmeasurementisthetesla(T)(1
1.1 This standard contains definitions of basic terms,
T=10 gauss).
conventions, and recommended practices for data presentation
2.4.1 The foregoing quantities are approximately connected
in the area of high-resolution resolution nuclear magnetic
by the following relation:
resonance (NMR) spectroscopy. Some of the basic definitions
apply to wide-line NMR or to NMR of metals, but in general
γ
ν 5 H (1)
o o
it is not intended to cover these latter areas of NMR in this 2π
standard. This version does not include definitions pertaining
where γ=the magnetogyric ratio, a constant for a given
to double resonance nor to rotating frame experiments.
nuclide (Note 2).The amplitude of the magnetic component of
1.2 The values stated in SI units are to be regarded as
the radio-frequency field is called H . Recommended units are
standard. No other units of measurement are included in this
millitesla and microtesla.
standard.
NOTE 2—This quantity is normally referred to as B by physicists. The
usage of H to refer to magnetic field strength in chemical applications is
2. Terminology Nomenclature and Basic Definitions
sowidelyacceptedthatthereappearstobenopointinattemptingtoreach
a totally consistent nomenclature now.
2.1 nuclear magnetic resonance (NMR) spectroscopy—that
NOTE3—Thisexpressioniscorrectonlyforbarenucleiandwillbeonly
form of spectroscopy concerned with radio-frequency-induced
approximatelytruefornucleiinchemicalcompounds,sincethefieldatthe
transitions between magnetic energy levels of atomic nuclei.
nucleus is in general different from the static magnetic field. The
discrepancy amounts to a few parts in 10 for protons, but may be of
2.2 NMR apparatus; NMR equipment—an instrument com-
−3
magnitude 1×10 for the heaviest nuclei.
prising a magnet, radio-frequency oscillator, sample holder,
and a detector that is capable of producing an electrical signal
2.5 NMR absorption line—a single transition or a set of
suitable for display on a recorder or an oscilloscope, or which
degenerate transitions is referred to as a line.
is suitable for input to a computer.
2.6 NMR absorption band; NMR band— a region of the
2.3 high-resolution NMR spectrometer—anNMRapparatus
spectruminwhichadetectablesignalexistsandpassesthrough
that is capable of producing, for a given isotope, line widths
one or more maxima.
that are less than the majority of the chemical shifts and
2.7 reference compound (NMR)—a selected material to
coupling constants for that isotope.
whose signal the spectrum of a sample may be referred for the
NOTE 1—By this definition, a given spectrometer may be classed as a
measurement of chemical shift (see 2.9).
high-resolutioninstrumentforisotopeswithlargechemicalshifts,butmay
2.7.1 internal reference (NMR)—a reference compound that
not be classed as a high-resolution instrument for isotopes with smaller
is dissolved in the same phase as the sample.
chemical shifts.
2.7.2 external reference (NMR)—areferencecompoundthat
2.4 basic NMR frequency, ν —the frequency, measured in
o
is not dissolved in the same phase as the sample.
hertz (Hz), of the oscillating magnetic field applied to induce
transitions between nuclear magnetic energy levels. The static
2.8 lock signal—the NMR signal used to control the field-
frequency ratio of the spectrometer. It may or may not be the
same as the reference signal.
2.8.1 internal lock—a lock signal which is obtained from a
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
material that is physically within the confines of the sample
mittee E13.15 on Analytical Data.
tube, whether or not the material is in the same phase as the
Current edition approved Nov. 1, 2011. Published January 2012. Originally
sample (an annulus for the purpose of this definition is
approved in 1969. Last previous edition approved in 2004 as E386–90(2004).
DOI: 10.1520/E0386-90R11. considered to be within the sample tube).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E386 − 90 (2011)
2.8.2 external lock—a lock signal which is obtained from a 3. Types of High-Resolution NMR Spectroscopy
material that is physically outside the sample tube. The
3.1 sequential excitation NMR; continuous wave (CW)
material supplying the lock signal is usually built into the
NMR—a form of high-resolution NMR in which nuclei of
probe.
different field/frequency ratio at resonance are successively
excited by sweeping the magnetic field or the radio frequency.
NOTE 4—An external lock, if also used as a reference, is necessarily an
external reference.An internal lock, if used as a reference, may be either
3.1.1 rapid scan Fourier transform NMR; correlation
an internal or an external reference, depending upon the experimental
spectroscopy—a form of sequential excitation NMR in which
configuration.
the response of a spin system to a rapid passage excitation is
2.8.3 homonuclear lock—a lock signal which is obtained
obtained and is converted to a slow-passage spectrum by
from the same nuclide that is being observed.
mathematical correlation with a reference line, or by suitable
2.8.4 heteronuclear lock—a lock signal which is obtained
mathematical procedures including Fourier transformations.
from a different nuclide than the one being observed.
3.2 broad-band excitation NMR—a form of high-resolution
2.9 chemical shift, δ—the defining equation for δ is the
NMRinwhichnucleiofthesameisotopebutpossiblydifferent
following:
chemical shifts are excited simultaneously rather than sequen-
tially.
∆ν
δ 5 310 (2)
3.2.1 pulse Fourier transform NMR—a form of broad-band
ν
R
excitation NMR in which the sample is irradiated with one or
whereν isthefrequencywithwhichthereferencesubstance
R
more pulse sequences of radio-frequency power spaced at
isinresonanceatthemagneticfieldusedintheexperimentand
uniform time intervals, and the averaged free induction decay
∆ν is the frequency of the subject line minus the frequency of
following the pulse sequences is converted to a frequency
the reference line at constant field. The sign of ∆ν is to be
domain spectrum by a Fourier transformation.
chosen such that shifts to the high frequency side of the
3.2.1.1 pulse Fourier difference NMR—a form of pulse
reference shall be positive.
Fourier transform NMR in which the difference frequencies
2.9.1 If the experiment is done at constant frequency (field
between the sample signals and a strong reference signal are
sweep) the defining equation becomes
extracted from the sample response prior to Fourier transfor-
∆ν ∆ν
mation.
δ 5 3 1 2 310 (3)
S D
ν ν
R R
3.2.1.2 synthesized excitation Fourier NMR— a form of
pulse Fourier NMR in which a desired frequency spectrum for
2.9.2 In case the experiment is done by observation of a
the exciting signal is Fourier synthesized and used to modulate
modulation sideband, the audio upper or lower sideband
the exciting radio frequency.
frequency must be added to or subtracted from the radio
3.2.2 stochastic excitation NMR—a form of broad band
frequency.
excitation NMR in which the nuclei are excited by a range of
2.10 spinning sidebands—bands, paired symmetrically
frequencies produced by random or pseudorandom noise
about a principal band, arising from spinning of the sample in
modulation of the carrier, and the frequency spectrum is
a field (dc or rf) that is inhomogeneous at the sample position.
obtained by Fourier transforming the correlation function
Spinning sidebands occur at frequencies separated from the
between the input and output signals.
principal band by integral multiples of the spinning rate. The
3.2.3 Hadamard transform NMR—a form of broad band
intensities of bands which are equally spaced above and below
excitation NMR in which the phase of the excitation signal is
the principal band are not necessarily equal.
switched according to a binary pseudorandom sequence, and
2.11 satellites—additional bands spaced nearly symmetri-
the correlation of the input and output signals by a Hadamard
cally about a principal band, arising from the presence of an
matrix yields an interference pattern which is then Fourier-
isotope of non-zero spin which is coupled to the nucleus being
transformed.
observed. An isotope shift is normally observed which causes
the center of the satellites to be chemically shifted from the
4. Operational Definitions
principal band. The intensity of the satellite signal increases
4.1 Definitions Applying to Sequential Excitation (CW)
with the abundance of the isotope responsible.
NMR:
2.12 NMR line width—the full width, expressed in hertz
4.1.1 field sweeping (NMR)—systematically varying the
(Hz), of an observed NMR line at one-half maximum height
magnetic field strength, at constant applied radio-frequency
(FWHM).
field, to bring NMR transitions of different energies succes-
2.13 spin-spin coupling constant (NMR), J—a measure, sively into resonance, thereby making available an NMR
expressed in hertz (Hz), of the indirect spin-spin interaction of
spectrum consisting of signal intensity versus magnetic field
different magnetic nuclei in a given molecule. strength.
4.1.2 frequency sweeping (NMR)—systematically varying
n
NOTE5—Thenotation J isusedtorepresentacouplingover nbonds
AB
the frequency of the applied radio frequency field (or of a
between nuclei A and B. When it is necessary to specify a particular
3 15
isotope, a modified notation may be used, such as, J ( NH). modulation sideband, see 4.1.4), at constant magnetic field
E386 − 90 (2011)
NOTE 9—Other parameters, such as rate of roll-off, width of passband,
strength, to bring NMR transitions of different energies suc-
orwidthandrejectionofcenterfrequencyincaseofanotchfilter,maybe
cessively into resonance, thereby making available an NMR
required to define filter characteristics adequately.
spectrum consisting of signal intensity versus applied radio
4.2.10 data acquisition rate; sampling rate; digitizing
frequency.
rate—the number of data points recorded per second.
4.1.3 sweep rate—therate,inhertz(Hz)persecondatwhich
4.2.11 dwell time—the time between the beginning of sam-
the applied radio frequency is varied to produce an NMR
pling of one data point and the beginning of sampling of the
spectrum. In the case of field sweep, the actual sweep rate in
next successive point in the FID.
microtesla per second is customarily converted to the equiva-
4.2.11.1 aperture time—the time interval during which the
lent in hertz per second, using the following equation:
sample-and-hold device is receptive to signal information. In
∆ν γ ∆H
5 · (4) most applications of pulse NMR, the aperture time is a small
∆t 2π ∆t
fraction of the dwell time.
4.1.4 modulation sidebands—bands introduced into the
NOTE 10—Sampling Time has been used with both of the above
NMR spectrum by, for example, modulation of the resonance
meanings. Since the use of this term may be ambiguous, it is to be
signals. This may be accomplished by modulation of the static
discouraged.
magneticfield,orbyeitheramplitudemodulationorfrequency
4.2.12 detection method—a specification of the method of
modulation of the basic radio frequency.
detection.
4.1.5 NMR spectral resolution—the width of a single line in
4.2.12.1 single-phase detection—a method of operation in
the spectrum which is known to be sharp, such as, TMS or
whichasinglephase-sensitivedetectorisusedtoextractsignal
benzene( H).Thisdefinitionincludessamplefactorsaswellas
information from a FID.
instrumental factors.
4.2.12.2 quadrature detection—a method of operation in
4.1.6 NMR integral (analog)—a quantitative measure of the
whichdualphase-sensitivedetectionisusedtoextractapairof
relative intensities of NMR signals, defined by the areas of the
FID’s which differ in phase by 90°.
spectral lines and usually displayed as a step function in which
4.2.13 spectral width—the frequency range represented
the heights of the steps are proportional to the areas (intensi-
without foldover. (Spectral width is equal to one half the data
ties) of the resonances.
acquisition rate in the case of single-phase detection; but is
4.2 Definitions Applying to Multifrequency Excitation
equal to the full data acquisition rate if quadrature detection is
(Pulse) NMR:
used.)
4.2.1 pulse (v)—to apply for a specified period of time a
4.2.14 foldover; foldback—the appearance of spurious lines
perturbation (for example, a radio frequency field) whose
in the spectrum arising from either (a) limitations in data
amplitude envelope is nominally rectangular.
acquisition rate or (b) the inability of the spectrometer detector
4.2.2 pulse (n)—a perturbation applied as described above.
to distinguish frequencies above the carrier frequency from
4.2.3 pulse width—the duration of a pulse.
those below it.
4.2.4 pulse flip angle—the angle (in degrees or radians)
NOTE11—Thesetwomeaningsof foldoverareincommonuse.Type (a)
through which the magnetization is rotated by a pulse (such as
is often termed “aliasing.” Type (b) foldover is obviated by the use of
a 90-deg pulse or π/2 pulse).
quadrature detection.
4.2.5 pulse amplitude—the radio frequency field, H,in
4.2.15 data acquisition time—the period of time during
tesla.
whichdataareacquiredanddigitized;equalnumericallytothe
NOTE 6—This may be specified indirectly, as described in 8.3.2.
product of the dwell time and the number of data points
4.2.6 pulse phase—the phase of the radio frequency field as
acquired.
measured relative to chosen axes in the rotating coordinate
4.2.16 computer-limited spectral resolution—the spectral
system.
width divided by the number of data points.
Note—This will be a measure of the observed line width
NOTE 7—The phase may be designated by a subscript, such as, 90° or
x
only when it is much greater than the spectral resolution
(π/2) .
x
defined in 4.1.5.
4.2.7 free induction decay (FID)—the time response signal
4.2.17 pulse sequence—a set of defined pulses and time
following application of an r-f pulse.
spacings between these pulses.
4.2.8 homogeneity spoiling pulse; homo-spoil pulse; inho-
mogeniz
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