Lezione tenuta al Convegno di Freising nel 2006

7/28/2019 Lezione tenuta al Convegno di Freising nel 2006

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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

[email protected]


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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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-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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-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


-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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-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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-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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-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

Lezione tenuta al Convegno di Freising nel 2006

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