A non-invasive NMR relaxometric characterization of the cyclododecane-solvent system inside porous...

Special issue research article

Received: 17 June 2014 Revised: 12 August 2014 Accepted: 16 August 2014 Published online in Wiley Online Library: 16 September 2014

(wileyonlinelibrary.com) DOI 10.1002/mrc.4144

Anon-invasiveNMR relaxometric characterizationof the cyclododecane–solvent system insideporous substrates†

F. Presciutti,a,b* B. Doherty,b,c C. Anselmi,b,c B. G. Brunetti,b A. Sgamellottia,b,c

and C. Milianib,c

With the aim of deepening the knowledge on the behavior of cyclododecane (CDD) as a temporary consolidant agent for weatheredstones, NMR longitudinal and transverse relaxation decays have been exploited to follow the distribution of cyclododecanesolutions into porous matrices. By measuring as function of time the relaxation decay constants of CDD solutions dropped ontoporous supports, it has been possible to differentiate the step encompassing the solvent evaporation, which determines theconsolidant migration within the matrix, from that governing the consolidant sublimation, which is related to the consolidationeffectiveness over time. Copyright © 2014 John Wiley & Sons, Ltd.

Keywords: temporary consolidant; cyclododecane; relaxation decays; single-side NMR sensor; Heritage Science

* Correspondence to: F. Presciutti, Dipartimento di Chimica, Università degli Studi diPerugia, Perugia, Italy. E-mail: [email protected]

† This article is published in Magnetic Resonance in Chemistry as a special issue on theNMR in Cultural Heritage by Donatella Capitani and Noemi Proietti (Istituto diMetodologie Chimiche, CNR Area della Ricerca di Roma, Monterotondo (Rome) Italy).

a Dipartimento di Chimica, Università degli Studi di Perugia, Perugia, Italy

b Centro di eccellenza SMAArt (Scientific Methodologies applied to Archaeology andArt) c/o Dipartimento di Chimica, Università degli Studi di Perugia, Perugia, Italy

c Istituto CNR di Scienze e Tecnologie Molecolari (ISTM) c/o Dipartimento diChimica, Università degli Studi di Perugia, Perugia, Italy

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Introduction

In the field of Heritage Science, there is a continuous search forinnovative materials that may prove to be useful and versatileas a protective and/or consolidant of weathered stone objects.However, the problem exists that often these materials are notalways adequately analytically characterized and tested beforetheir subsequent employment. One such compound, whichsince 1995 has proved successful, is cyclododecane (CDD), thatdue to its chemico–physico properties may be used as a tempo-rary protective, consolidant, adhesive and binder and has beenefficiently applied to wall paintings, ceramics, plastics, paperand metals. In fact, CDD is a solid substance, which, at roomtemperature and over a certain time period, spontaneously sub-limes, guaranteeing the principle of reversibility of the treatmentwithout requiring the use of other substances for its adequateremoval. This fact is of fundamental interest to conservators,especially in cases of emergency, that when due to naturalevents, it is necessary to quickly secure works of art, or when,rather more simply, they must be removed from a site andtransported to another for restoration interventions.

Our main interest in recent years has been to test CDD both asa feasible protective[1] and consolidant,[2] using three substratesobserving different porosities, namely, Carrara marble, Leccestone and mortar along with three solvents with different boilingpoints, (cyclohexane, n-heptane and n-decane). Because of the in-trinsic peculiarity of the sublimation process, the application ofnon-invasive techniques, specifically portable FTIR spectrometryequipped with a fiber optic extension and portable unilateral1HNMR profilometry, have been exploited in order to avoid anykind of interference and acceleration of the rate of sublimation.In the first case,[1] the sublimation rates of CDD film coatings ona Carrara marble substrate as an indication of its protective actionhas been evaluated. The sublimation of CDD was followedthrough characteristic C–H stretching overtone bands by infrared

Magn. Reson. Chem. 2015, 53, 27–33

spectroscopy determining the overall efficiency and duration ofthe film formedwith each different solvent. The NMR profiling tech-nique has been able to further ascertain the non-penetration ofCDD within the marble matrix as well as to estimate the thicknessof each resulting film and to follow each separate sublimationprocess that corresponds well with data collected by infrared.The kinetics of sublimation show a quasi-linear trend and similarbehavior that results independent of the solvent employed tocreate the film.

In second study,[2] the consolidant action of CDD solutions afterdropping into porous substrates such as Lecce stone and mortarswas disclosed. The applied organic materials can be suitably moni-tored by infrared spectroscopy over the solution evaporationprocess as it emerges from the stone matrix. NMR in-depthprofilometry allowed the monitoring of CDD solutions penetrationdepth as well as the visualization of their behavior inside thesamples. It was observed that CDD solutions adopt a differentsublimation pattern depending on the chosen lithotype, yet differ-ences too have been found regarding its penetration depth. Never-theless, a pertinent difficulty encountered in these systems hasbeen to adequately distinguish between the evaporation of the

Copyright © 2014 John Wiley & Sons, Ltd.

Figure 1. (a) Longitudinal relaxation decay collected at different times of cyclododecane (CDD) in n-heptane solution. (b) Transverse relaxation decaycollected at different times of cyclododecane CDD in n-heptane solution. (c) Longitudinal relaxation decay collected at different times of cyclododecaneCDD in n-decane solution. (d) Transverse relaxation decay collected at different times of cyclododecane in n-decane solution.

Table 1. (a) Exponential fitting of transversal and longitudinal decays collected at different times of the cyclododecane in n-heptanesolution and (b) exponential fitting of transversal and longitudinal decays collected at different times of the cyclododecane in n-decanesolution

(a) CDD in n-heptane T2 T1

h0 T2a= 51.7±0.3 886±29

h24 78% T2a= 0.44±0.09 22% T2b =3.7±0.1 44± 1

h36 78% T2a= 0.39±0.09 22% T2b =3.38±0.09 39±1

(b) CDD in n-decane T2 T1

h0 T2a= 54.6±0.4 886±26

h24 48% T2a= 0.55±0.01 52% T2b =41.2±0.4 299±4

h48 82% T2a= 0.541±0.006 18% T2b =5.59±0.08 45.7± 0.5

h72 79% T2a= 0.509±0.006 21% T2b =4.58±0.06 44.4± 0.4

h84 76% T2a= 0.41±0.08 24% T2b =3.1±0.3 38.1± 0.8

F. Presciutti et al.

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carrier solvent and sublimation of the pure CDD. In order to over-come this problem, this contribution necessarily explores aimedNMR studies concerning the estimation of relaxation decay con-stants (longitudinal, T1 and transverse T2) of solid CDD, CDD solu-tions and CDD solutions dropped onto porous supports with themain objective in differentiating between the step encompassingthe solvent evaporation from that governing the sublimation.Longitudinal and transverse relaxation decays can describe

many properties of a system, and this typology of study has alsofound many applications in the field of Heritage Science.[3,4] Inparticular, regarding the study of porous matrix, as stones or muralpaintings, NMR decays are related to the dimensions of the pores and

wileyonlinelibrary.com/journal/mrc Copyright © 2014 Jo

can ultimately give information on the effectiveness of protective orconsolidant.[5–7] In the field of conservation of paper they can give in-formation concerning the degradation state[8] and may also be usefulin suggesting suitable cleaning interventions for example for fattystains, often present in ancient paper, thanks to the individuation ofthe nature of the oil responsible of the stain.[9] In a wooden matrix,T1 and T2 can indicate the degree of degradation,[10] the moistercontent and the direction of strain of thewood.[11] The spin–spin decayrelated to a 1H stratigraphy of a painting can suggest the presence ofdifferent layers constituted by different organic materials allowing forsubsequent selective microsampling.[12–14] Moreover the spin–spinand spin–lattice relaxations can also be affected by the interaction

hn Wiley & Sons, Ltd. Magn. Reson. Chem. 2015, 53, 27–33

Figure 2. (a) NMR proton density distribution collected at different times of CDD in n-heptane solution dropped inside Lecce stone. (b) Transverserelaxation decay collected (in the position of the maximum of the proton density distribution) at different times of cyclododecane in n-heptanesolution dropped inside Lecce stone. (c) Longitudinal relaxation decay collected (in the position of the maximum of the proton densitydistribution) at different times of CDD in n-heptane solution dropped inside Lecce stone.

Table 2. Exponential fitting of transversal and longitudinal decayscollected at different times of the cyclododecane in n-heptane solution,dropped inside the Lecce stone

T2 T1

h0 T2a = 30.8± 0.2 177±10

h24 56% T2a = 0.92± 0.02 44% T2b =27.4± 0.2 111±6

h48 65% T2a = 0.88± 0.01 35% T2b =26.0± 0.2 69±3

h120 80% T2a = 0.43± 0.01 20% T2b =4.7± 0.1 40±2

h168 79% T2a = 0.36± 0.08 21% T2b =3.2± 0.1 38±1

NMR relaxometric characterization of the cyclododecane–solvent system

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between the binder and pigment.[15] Finally, these two parameters canbe used to describe plastic, polymer, rubber and gum, all verycommon materials in modern and contemporary art.[16,17]

In this contribution, the longitudinal and transversal decays areuseful in distinguishing between solution and solid CDD contribu-tions. Particularly when solid CDD is present in the pores, it canact as a successful temporary consolidant. Because the perma-nence of the CDD inside the porosity following the application ofa permanent treatment that could block its free sublimation canultimately cause stress and breaking of the porous wall, it is ofcritical importance to develop a working methodology that maybe used directly in situ on non-movable artworks, while simulta-neously highlighting the advantages of portable instrumentationfor the online monitoring of conservation treatments.

Magn. Reson. Chem. 2015, 53, 27–33 Copyright © 2014 John W

Experimental

Unilateral NMR

All NMR measurements were performed using an ACT (AachenCenter of Technology) NMR-MOUSE® controlled by a BrukerMinispec (Bruker BioSpin, Rheinstetten, Germany) operating at17.6MHz 1H resonance frequency with a field strength of 0.411Tand a gradient G of 20 Tm-1 along the depth direction and a π/2pulse of 4μs. This sensor generates, in the probed area(15×20mm) and 3mm away from the radiofrequency (RF) coil,[18]

a magnetic field with an extremely uniform gradient to resolve thenear surface structure of arbitrary large objects. Proton-driven NMRprofiles were carried out by repositioning, thanks to a lift thatmoves the sensor with a spatial resolution of 10μm, the single-sided sensor in steps of 100μm with a spatial resolution of150μm. The amplitude of each experimental point in the stratigra-phy was obtained as the average of the intensity of the first fourechoes acquired with a CPMG sequence. In the position wherethe maximum of intensity was registered, longitudinal and trans-verse relaxation decays were collected. The transverse relaxationdecays of 1H were measured using the Carr–Purcell–Meiboom–Gill(CPMG)[19,20] pulse sequence with echo times of 34μs and acquisi-tion times of 6μs, which, in the presence of the field gradient G,defines a nominal resolution of about 150μm. The magnetic fieldof the NMR-MOUSE is highly inhomogeneous, implying that theRF pulses are disturbed by resonance offsets in the selectedvolume. This also causes that the echo decay from the CPMG

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Figure 3. (a) NMR proton density distribution collected at different times of CDD in n-decane solution dropped inside Lecce stone. (b) Transverse relaxationdecay collected (in the position of the maximum of the proton density distribution) at different times of cyclododecane in n-decane solution dropped insideLecce stone. (c) Longitudinal relaxation decay collected (in the position of the maximum of the proton density distribution) at different times of CDD in n-decane solution dropped inside Lecce stone.

Table 3. Exponential fitting of transversal and longitudinal decays col-lected at different times of the cyclododecane in n-decane solution,dropped inside the Lecce stone

T2 T1

h0 33% T2a = 1.48±0.06 67% T2b =42.3±0.3 180±17

h48 48% T2a = 1.33±0.07 52% T2b =38.0±0.3 109±5

h90 67% T2a = 0.99±0.02 33% T2b =32.2±0.3 70±4

h168 77% T2a = 0.90±0.01 23% T2b =30.8±0.5 50±2

h236 78% T2a = 0.37±0.08 22% T2b =3.34±0.05 39±1


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sequence only approximates the decay in a homogeneous mag-netic field, and the T2 relaxation times are in the present casereferred to as T2eff.

[21] The recycle delay, number of scans, andnumber of echoes were adjusted to provide the optimum signal-to-noise ratio and to optimize the CPMG decay curve. The longitu-dinal relaxation decay was measured as already described inprevious article.[13] The experimental data were fit according tothe following equation:

Y ¼ C0 þX

Wi exp �t=Ti½ �

where n is the number of components of the decay of the magne-tization,Wi is the weight of the ith component, C0 is the offset valuewhich accounts for the noise of the measurement, and Ti is therelaxation time of the ith component.


Sample preparation

Commercially pure CDD was characterized both in spray and pelletform. The former was just applied on a Petri dish, and the latter wasfirst melted and then left to form a solid coating at room tempera-ture. A further investigation regards the study of the CDD dissolvedin a solution of n-heptane and of n-decane (2/3:w/v). Finally, a 3-mlsolution of CDD in the same two solvents (2/3:w/v) were dropped byPasteur pipette directly onto the surface of the Lecce stone andmortar models.[2] Lecce stone is a calcarenite, around 95% of whichis composed by CaCO3 and the rest by silicates. Its open porosity isaround 37% (pore radius: 8% 2μm, 35% 1μm, 17% 0.5μm, 12%0.25μm, 10% 0.12μm, 7% 0.064μm and the rest of porosity showdimensions smaller than the last one.). The mortar models were ob-tained by mixing 75% Ca(OH)2 and 25% SiO2 (quartz). Its open po-rosity is around 39% (pore radius: 36% 8μm, 18% 16μm, 9%32μm, 5% 4 and 2μm, and the rest of porosity is characterized bydimensions smaller than the last one). Cyclohexane was excludedas a useful solvent for this system because of its rapid rate of evap-oration, which does not permit penetration of the solution insidethe matrix.[2] Each sample was stored at room temperature and at30 to 40% relative humidity in order to monitor CDD sublimation.

Results and discussion

As had already been noted,[2] the CDD solution dripped onto the sur-face of a porous matrix penetrates inside this and then, depending


Figure 5. (a) NMR proton density distribution collected at different times of CDD in n-decane solution dropped inside mortar matrix. (b) Transverserelaxation decay collected (in the position of the maximum of the proton density distribution) at different times of CDD in n-decane solution droppedinside mortar matrix. (c) Longitudinal relaxation decay collected (in the position of the maximum of the proton density distribution) at different times ofcyclododecane in n-decane solution dropped inside mortar matrix.

Figure 4. (a) NMR proton density distribution collected at different times of cyclododecane in n-heptane solution dropped inside mortar matrix. (b)Transverse relaxation decay collected (in the position of the maximum of the proton density distribution) at different times of CDD in n-heptane solutiondropped inside mortar matrix. (c) Longitudinal relaxation decay collected (in the position of the maximum of the proton density distribution) at differenttimes of cyclododecane in n-heptane solution dropped inside mortar matrix.


Magn. Reson. Chem. 2015, 53, 27–33 Copyright © 2014 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/mrc

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Table 4. Exponential fitting of transversal and longitudinal decayscollected at different times of the cyclododecane in n-heptane solution,dropped inside a mortar matrix

T2 T1

h0 77% T2a= 0.84±0.01 23% T2b = 47±1 73±5

h24 80% T2a= 0.66±0.06 20% T2b = 5±1 42±2

h48 76% T2a= 0.39±0.4 24% T2b = 3.0±0.4 39±1

Table 5. Exponential fitting of transversal and longitudinal decayscollected at different times of the cyclododecane in n-decane solution,dropped inside a mortar matrix

T2 T1

h0 64% T2a = 0.61± 0.02 36% T2b =41.2± 0.7 191±27

h24 72% T2a = 0.73± 0.02 28% T2b = 50±1 90±6

h96 84% T2a = 0.8± 0.1 16% T2b = 44±1 58±3

h192 74% T2a = 0.49± 0.03 26% T2b =3.8± 0.2 42±1

h216 71% T2a = 0.39± 0.03 29% T2b =3.1± 0.1 38±1


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on the relative porosity, it either tends to rise towards the surface byevaporation of the solvent or tends to disappear without anypreferential direction. In order to try to separate the solventcontribution from that due to the sublimation of the solidifiedCDD inside the porous matrix, the system was characterizedusing the relaxation times as screening factors. The first stepregarded the collection of the relaxation times T1eff and T2eff ofboth the pure CDD commercial products. The collected decaytimes are perfectly superimposable, and the values of the fittingobtained are as follows: 78% T2aeff = 0.40 ± 0.08 and 22% T2beff =3.28 ± 0.09, and T1eff = 39 ± 1.To study the interaction with the solvent, the CDD was dissolved

n-heptane and n-decane, and then a 3-ml solution was placed on aPetri dish where the T1eff and T2eff were measured every 12h. Theresults obtained are shown in Fig. 1a–d, and the fittings of thedecay times are reported in Table 1.As expected, the resulting relaxation times of the two solutions

are rather long, so gradually, as the solvent evaporates and theCDD solidifies, the decays are shortened up to the value of theCDD pure and remain such until the signal/noise ratio is satisfied.As it is possible to observe, the solution in n-heptane takes abouthalf the time to solidify compared to that in the n-decane becauseof its lower boiling point.In Fig. 2a is possible to observe the profiles obtained by

dripping a solution of CDD in n-heptane on the surface of a sam-ple of Lecce stone.As noted in our previous study,[2] the solution penetrates into the

stone and then rises toward the surface where a maximum signalcan be observed, in this case after 48h, and then this signal startsto decrease until it disappears completely. As can be seen in Fig. 2band c, the decays are long in the first hours supporting the hypoth-esis that the liquid solution moves through the sample from theinside outwards, then, when the signal starts to decrease, thedecays become notably shorter, indicating the formation of a solidphase with T1eff and T2eff values coinciding with those of the pureCDD, as can be noted in Table 2. The same behavior can beobserved for the solution in n-decane though, as expected for its


higher boiling point, the system remains liquid longer, and themaximum signal is recorded after 168 h (Fig. 3a). At 236 h, the signalon the surface decreases, and the T1eff and T2eff already correspondto those of the pure CDD (Fig. 3b and c and Table 3) and remainsuch until the signal/noise ratio remains acceptable.

Finally, this behavior on a matrix with pores as large asthe mortar has also been verified. As hypothesized in theprevious study,[2] in this case, the solvent evaporates in everydirection without solution migration to the surface but, as canbe seen in Figs 4a and 5a, leaves the solid CDD settled moreinside. As can be observed in Fig. 4b and c and in Table 4, inthe case of the solution in n-heptane after 48 h, the solvent isalready completely evaporated and the CDD solid starts tosublime. Regarding n-decane, the kinetics of evaporation ofthe solvent is not accelerated by the increased size of the pores;in fact, as can be observed in Fig. 5b and c and Table 5, theCDD solidifies almost in the same time as that observed forLecce stone.

Conclusion

In this work, it has been demonstrated that the technique ofNMR relaxometry is highly suitable to study, in a completelynon-invasive way, systems of this type. It is shown that solidCDD, whether it is applied through spraying or melting, showsentirely comparable relaxation times. The interaction of CDDwith the solvent has been analyzed, and it has been observed,as a result of evaporation of the solvent, that here the solidCDD is characterized by the same relaxation times as thatobserved for the pure CDD. Proportionate results are obtainedtoo for matrices with small and very large pores. It has thus beenshown that it is possible to separate the contribution of thesolvent from that of the solid CDD that is deposited inside thepores. By collecting T1eff and T2eff relaxation times, it is feasibleto determine the exact length of time when the solvent iscompletely evaporated and, following such, how long the CDD,which at this point is solidified inside the porosity, takes tosublime completely. Therefore, it is possible to evaluate theconsolidation capability of the CDD and decide the right timefor the permanent treatment. In our experience the phases thatcharacterize the process are strongly influenced by many factorssuch as nature and porosity of the stone, temperature, humidity,and ventilation; therefore, it is not possible to draw a conclusionabout the duration of the single phases. For this reason, themonitoring of the treatment is strongly recommended. This kindof study becomes very important when it is applied directly onimmovable artworks because it allows one to follow in a non-invasive way the entire process, guaranteeing the safety of theobject itself.

Acknowledgements

This work was carried out within Eu-ARTECH, an IntegratedInfrastructures Initiative supported by the 6th Framework Pro-gramme of the European Union (Contract RII3-CT-2004-506171). Part of this work was supported by the regional project‘Sviluppo e tutela conservativa—Progetto1—primo atto inte-grativo APQ-Umbria Tutela e Prevenzione nei Beni Culturali’.The authors gratefully acknowledge the support of CHARISMA,a project by the EU commission within the program capacities(FP7Research Infrastructures GA N.228330).



References[1] C. Anselmi, F. Presciutti, B. Doherty, B. G. Brunetti, A. Sgamellotti,

C. Miliani. Appl. Phys. A 2011, 104(1), 401–406.[2] C. Anselmi, F. Presciutti, B. Doherty, B. G. Brunetti, A. Sgamellotti,

C. Miliani. J. Cultural Heritage 2014. doi:10.1016/j.culher.2014.03.006.[3] D. Capitani, V. Di Tulio, N. Proietti. Prog. Nucl. Magn. Reson. Spectrosc.

2012, 64, 29–69.[4] B. Blumich, F. Casanova, J. Perlo, F. Presciutti, C. Anselmi, B. Doherty.

Acc. Chem. Res. 2010, 43, 761.[5] N. Proietti, D. Capitani, S. Cozzolino, M. Valentini, E. Pedemonte,

E. Princi, S. Vicini, A. L. Segre. J. Phys. Chem. B 2006, 110, 23719–23728.[6] V. Di Tullio, N. Proietti, D. Capitani, I. Nicolini, A. M. Mecchi. Anal. Bioanal.

Chem. 2011, 400, 3151–3164.[7] V. Di Tullio, N. Proietti, M. Gobbino, D. Capitani, R. Olmi, S. Priori,

C. Riminesi, E. Giani. Anal. Bioanal. Chem. 2010, 396, 1885–1896.[8] K. Castro, E. Princi, N. Proietti, M. Manso, D. Capitani, S. Vicini,

J. M. Madariaga, M. L. De Carvalho. Nucl. Instrum. Methods Phys. Res. B2011, 269, 1401–1410.

[9] E. Del Federico, S. A. Centeno, C. Kehlet, P. Currier, D. Stockman,A. Jerschow. Anal. Bioanal. Chem. 2010, 396(1), 213–220.

Magn. Reson. Chem. 2015, 53, 27–33 Copyright © 2014 John W

[10] S. Viel, D. Capitani, N. Proietti, F. Ziarelli, A. L. Segre. Appl. Phys. A 2004,79, 357–361.

[11] L. Senni, M. Caponero, C. Casieri, F. Felli, F. De Luca.Wood Sci. Technol.2010, 44, 165–175.

[12] F. Presciutti, J. Perlo, F. Casanova, S. Glöggler, C. Miliani, B. Blümich,B. G. Brunetti, A. Sgamellotti. Appl. Phys. Lett. 2008, 93(3), 033505.

[13] N. Proietti, F. Presciutti, V. Di Tullio, B. Doherty, A. M. Marinelli,B. Provinciali, N. Macchioni, D. Capitani, C. Miliani. Anal. Bioanal.Chem. 2011, 399(9), 3117.

[14] V. Di Tullio, D. Capitani, F. Presciutti, G. Gentile, B. G. Brunetti, N. Proietti.Anal. Bioanal. Chem. 2013, 405, 8669–8675.

[15] E. Del Federico, S. A. Centeno, C. Kehlet, K. Ulrich, A. Yamazaki-Kleps,A. Jerschow. Appl. Magn. Res. 2012, 42(3), 363–376.

[16] K. Ulrich, S. A. Centeno, J. Arslanoglu, E. Del Federico. Prog. OrganicCoatings 2011, 71, 283–289.

[17] C. Kehlet, E. Del Federico, H. Schahbaz, A. Catalano, J. Dittmer,N. C. Nielsen. Anal. Methods 2013, 5, 4480.

[18] J. Perlo, F. Casanova, B. Blümich. J. Magn. Reson. 2005, 176, 64.[19] H. Y. Carr, E. M. Purcell. Phys. Rev. 1954, 94, 630.[20] S. Meiboom, D. Gill. Rev. Sci. Instrum. 1958, 29, 688.[21] B. Blümich, F. Casanova, J. Perlo. Prog. Nucl. Magn. Reson. Spectrosc.

2008, 52, 197.

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