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RAPID MEASUREMENT OF 1H 90 PULSE INTHE SOLID STATE NMR VIA CROSS
POLARIZATION
Pellegrino Conte
Dipartimento di Scienze del Suolo, della Pianta edellAmbiente
Universit di Napoli Federico II
Via Universit 100, 80055 Portici (Na), ITALY
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Solid state NMR spectroscopy is widely applied inmany fields:
1. Analysis of structures and molecular dynamics oftechnologically relevant polymers
2. Analyses of environmentally significative organic and inorganicmaterials
3. Control of the quality of industrial products such aspharmaceutical ones and polymer blends
4. Studies of reactions in the solid state
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Solid state NMR spectroscopy in Soil Science
1. Analyses of the organic and inorganic soil components2. Quantification of the different chemicals belonging to natural
organic matter (humic substances)
3. Evaluation of the transformation of soil organic matter asaffected by soil management, soil formation, soiltransformation and so on
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Classical CPMAS 13C NMR sequence
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-1
0
1
0
2
Positive NMR Signals
Negatve NMR Signals
Null NMR Signals
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2.96 s
Classical 1H 90 pulse calibration on glycine
The 1H 90 pulse
is that obtainedby halving the180 pulsemeasured byinversion recovery
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Alternative method to measure 1H 90 pulse: P360 sequence
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Chemical Shift (ppm)
-1000100200300
176
43
A
B
Glycine
Classical CPMAS 13Cspectrum with 1H 90
pulse of 2.96 s
P360 CPMAS 13C spectrum.1H 360 pulse: 4 x 2.96 s=11.84 s
NH2
O
OH
176 ppm43 ppm
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Theoric pulse length
Pulse length affected bycircuit impedance
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Due to the circuitimpedance, the inversion
recovery experiment onglycine provided 1H 90pulse that was too long.
In fact, the P360 experimentrevealed a residual NMRsignal of both carbons ofglycine.
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4x90 pulse sequence to measure 1H 90 pulse
As suggested by the NMRproducers for the liquid stateNMR, distortion of pulses due tocircuit impedances can be
overcome by applying a pulse trainmade by small pulses
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4x90 pulse sequence to measure 1H 90 pulse
Bruker language
Classical CP sequence 4 x 90 sequence
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Chemical Shift (ppm)
-1000100200300
176
43
A
B
C
Glycine
Classical CPMAS 13Cspectrum with 1H 90pulse of 2.96 s
4x90 CPMAS 13C
spectrum.1
H 90 pulse:2.80 s
P360 CPMAS 13C spectrum.1H 360 pulse: 4 x 2.96s= 11.84 s
NH2
O
OH
176 ppm43 ppm
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Chemical Shift (ppm)
-1000100200300
79
33
24
14
SDS
A
B
C
Classical CPMAS 13Cspectrum with 1H 90pulse of 2.96 s
4x90 CPMAS 13C
spectrum. 1H 90 pulse:2.80 s
P360 CPMAS 13C spectrum.1H 360 pulse: 4 x 2.96s= 11.84 s
OC
H2
CH2
S
O O
O C
H2
CH3
n
n=9
79 ppm
33 ppm
24 ppm
14 ppm
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A
B
C
Chemical Shift (ppm)
-1000100200300
CMC
178
104
74
62
12
3
4
5
O
OH
O
6
OH
O
CH27
O
O
O
*
*
n
178 ppm
104 ppm
C2-C6
62 ppm
A. CP spectrum of CMCobtained with a protonpulse of 2.80 s
B. CMC spectrum acquiredwith the 4 x 90 pulsesequence and a 2.80 sproton pulse
C. as in B. but with a protonpulse of 2.78 s;
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Chemical Shift (ppm)
-1000100200300
HMB
132
17
A
B
C
CH3
CH3
CH3
CH3
CH3
CH3
-CH3-Car
A. CP spectrum ofHMB with 1H pulseof 2.80 s
B. 4 x 90 HMBspectrum with 1Hpulse of 2.80 s
C. 4 x 90 HMBspectrum with 1Hpulse of 2.83 s.
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Chemical Shift (ppm)
-1000100200300
pepsine
A
B
172
128
10792
74
71
61
54
40 33
25
A. CP spectrum ofpepsine obtained with
a proton pulse of2.80 s
B. pepsine spectrumacquired with the 4 x90 pulse sequence
and a 2.80 s protonpulse;
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Chemical Shift (ppm)
-1000100200300
HA
A
B
C
173
129
102
7252
33
A. CP spectrum of HAwith 1H pulse of2.80 s
B. 4 x 90 HAspectrum with 1Hpulse of 2.80 s
C. 4 x 90 HAspectrum with 1Hpulse of 2.78 s.
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CONCLUSIONS
1. The standard calibration by inversion recoveryprovided a too long 1H 90 pulse
2. Only few attempts were needed to find thecorrect 1H 90 pulse by 4x90 pulse sequence
3. The 4x90 pulse sequence was successfully and
rapidly applied on very complex organic systemssuch as a protein (pepsine) and a humic acid
4. The 4x90 pulse sequence can efficaciously
replace the standard calibration with theinversion recovery routine
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