2.1 General Tables
7
2.1.3 Volume Susceptibilities and Corrections for External
References in NMR Spectroscopy [2, 3]
The local magnetic field depends on the volume susceptibility χ of the medium. The
observed chemical shifts δ obs must be corrected for the difference between the
magnetic susceptibilities of the reference and probe if the reference is inserted in a
cylindrical capillary into the sample tube (external reference). For superconducting
magnets, in which the magnetic field is parallel to the sample tube, the corrected
value δ corr is:
In instruments with permanent magnets and electromagnets, the magnetic field is
perpendicular to the sample tube. Here the following equation applies:
Example: If the sample is a D 2 O solution and TMS sealed in a capillary is
used as external reference, δ corr = δ obs + 0.62 for superconducting magnets and
δ corr = δ obs - 0.31 for instruments with permanent magnets or electromagnets.
Compound
Volume susceptibility × 10 6
acetic acid
-0.553
acetone
-0.457
acetonitrile
-0.532
ammonium chloride
(satd. in H 2 O)
-0.769
ammonium nitrate
(satd. in H 2 O)
-0.722
benzene
-0.615
bromobenzene
-0.744
bromoform
-0.941
carbon disulfide
-0.693
carbon tetrachloride
-0.684
chlorobenzene
-0.684
chloroform
-0.735
cyclohexane
-0.608
dibromomethane
-0.935
diethyl ether
-0.531
diisopropyl amine
-0.598
dimethyl sulfoxide
-0.618
1,4-dioxane
-0.612
ethanol
-0.576
Compound
Volume susceptibility × 10 6
ethyl acetate
-0.553
n-hexane
-0.568
methanol
-0.529
methylene chloride
-0.728
nitric acid
(1 M in H 2 O)
-0.715
nitric acid
(70% w/w in H 2 O)
-0618
nitrobenzene
-0.604
nitromethane
-0.391
pyridine
-0.605
sodium nitrite
(satd. in H 2 O)
-0.729
sulfuric acid (100%)
-0.723
toluene
-0.619
1,1,2,2-tetrachloroethane
-0.853
tetramethylsilane
-0.543
trifluoroacetic acid
-0.583
water, H 2 O
-0.716
water, D 2 O
-0.705
δ
δ
π χ
χ
δ
χ
χ
(
)
(
)
=
−
−
=
−
−
2
3
2.09
corr
obs
reference
s ample
obs
reference
s ample
δ
δ
π χ
χ
δ
χ
χ
(
)
(
)
=
+
−
=
+
−
4
3
4.19
corr
obs
reference
s ample
obs
reference
s ample
7
2.1.3 Volume Susceptibilities and Corrections for External
References in NMR Spectroscopy [2, 3]
The local magnetic field depends on the volume susceptibility χ of the medium. The
observed chemical shifts δ obs must be corrected for the difference between the
magnetic susceptibilities of the reference and probe if the reference is inserted in a
cylindrical capillary into the sample tube (external reference). For superconducting
magnets, in which the magnetic field is parallel to the sample tube, the corrected
value δ corr is:
In instruments with permanent magnets and electromagnets, the magnetic field is
perpendicular to the sample tube. Here the following equation applies:
Example: If the sample is a D 2 O solution and TMS sealed in a capillary is
used as external reference, δ corr = δ obs + 0.62 for superconducting magnets and
δ corr = δ obs - 0.31 for instruments with permanent magnets or electromagnets.
Compound
Volume susceptibility × 10 6
acetic acid
-0.553
acetone
-0.457
acetonitrile
-0.532
ammonium chloride
(satd. in H 2 O)
-0.769
ammonium nitrate
(satd. in H 2 O)
-0.722
benzene
-0.615
bromobenzene
-0.744
bromoform
-0.941
carbon disulfide
-0.693
carbon tetrachloride
-0.684
chlorobenzene
-0.684
chloroform
-0.735
cyclohexane
-0.608
dibromomethane
-0.935
diethyl ether
-0.531
diisopropyl amine
-0.598
dimethyl sulfoxide
-0.618
1,4-dioxane
-0.612
ethanol
-0.576
Compound
Volume susceptibility × 10 6
ethyl acetate
-0.553
n-hexane
-0.568
methanol
-0.529
methylene chloride
-0.728
nitric acid
(1 M in H 2 O)
-0.715
nitric acid
(70% w/w in H 2 O)
-0618
nitrobenzene
-0.604
nitromethane
-0.391
pyridine
-0.605
sodium nitrite
(satd. in H 2 O)
-0.729
sulfuric acid (100%)
-0.723
toluene
-0.619
1,1,2,2-tetrachloroethane
-0.853
tetramethylsilane
-0.543
trifluoroacetic acid
-0.583
water, H 2 O
-0.716
water, D 2 O
-0.705
δ
δ
π χ
χ
δ
χ
χ
(
)
(
)
=
−
−
=
−
−
2
3
2.09
corr
obs
reference
s ample
obs
reference
s ample
δ
δ
π χ
χ
δ
χ
χ
(
)
(
)
=
+
−
=
+
−
4
3
4.19
corr
obs
reference
s ample
obs
reference
s ample