CRAMPS technique

Although the CRAMPS technique (Combined Rotation and Multiple-Pulse Spectroscopy) was developed in the 1970 s23,24,25 it lasted up to 1988 before Bronnimann26 was able to produce well resolved H NMR spectra of the silica surface. Bronnimann s technique was further developed by Haukka and co-workers27,28 in 1993. 

Figure 11 Line narrowing by the CRAMPS technique of the 270 MHz H NMR spectrum of a dehydrated HY zeolite, (a) Static f>owder spectrum (b) MAS spectrum at 2.5 kHz rotation frequency (sealed glass ampoule). (From Ref. 25c.)...

To remove H- H dipolar effects one can apply the CRAMPS technique, in which a multiple-pulse sequence is used to average the dipolar interaction [51,52] while MAS is employed simultaneously to average the chemical shift anisotropy (CSA) [53]. Figure 11 illustrates the CRAMPS approach. 

With oil shales, the application of the CRAMPS technique is virtually nonexistent. To the author s knowledge, the only published CRAMPS spectra of an oU shale and its kerogen concentrate are shown in Fig. 20. Hie H spectra of the kerogen concentrate exhibit a narrower line width than the raw oil shale, analogous to that observed in the C spectra (Fig. 16). 

One should note that the CRAMPS technique is not necessarily a panacea for H NMR studies on surfaces, or for any other type of sample. Dynamics associated with motion and/or chemical reactions with a time constant that is comparable to the cycle time of the multiple-pulse sequence interferes with a multiple pulse averaging of H- H dipolar interactions [3b,4f]. Of course, an analogous problem can also arise with MAS, for which the critical period is i as. where v as is the MAS frequency [26]. To quench this kind of dynamic interference with the linenarrowing efficiency of any cyclic technique, like MAS and/or a multiple-pulse sequence, one would have to... 

While in the past the CRAMPS technique was so demanding technically that very few laboratories were... 

With the recent progress in NMR hardware development, the novel methodological approaches have appeared. Figure 2.1 shows the new sequences such as PMLG [13], DUMBO [14], SAM-3 [15] which are easy to setup and can be performed under high spinning rate of samples [16]. Modem CRAMPS techniques can be applied in direct and indirect dimension what gives opportunity to carry out correlation experiments. 

C. Coelho, J. Rocha, P.K. Madhu, L. Mafia, Practical aspects of Lee—Goldburg based CRAMPS techniques for high-resolution H NMR spectroscopy in solids implementation and apphcations, J. Magn. Reson. 194 (2) (2008) 264—282. 

One final technical improvement in soHd-state nmr is the use of combined rotational and multiple pulse spectroscopy (CRAMPS) (2), a technique which also requires a special probe and permits the acquisition of high resolution H and X nucleus nmr from soHds. The combination of these methods permits adapting most of the 1-D and 2-D experiments previously described for Hquids to the soHd phase. 

WARNING Anaphylactic Rxns w/ use use only if oral Fe not possible administer where resuscitation techniques available Uses Fe deficiency when cannot supl PO Action Fe supl Dose Adul. Iron defic anemia Estimate Fe deficiency, give 25-100 mg IM/IV /d until total dose total dose (mL) = [-.0442 x (desired Hgb - observed Hgb) x LBW] + (0.26 x LBW) Iron replacement, blood loss Total dose (mg) = blood loss (mL) x Hct (as decimal fraction) max 100 mg/d Peds >4 mo. As for adults max 0.5 mL (wt <5 kg), 1 mL (5-10 kg), 2 mL (>10 kg) p dose IM or direct IV Caution [C, M] Contra Anemia w/o Fe deficiency. Disp Inj SE Anaphylaxis, flushing, dizziness, inj site inf Rxns, metallic taste Interactions X Effects W/ chloramphenicol, X absorption of oral Fe EMS Anaphylactic Rxns common taking oral Fe t risk of tox and SEs OD May cause N/V, HA, muscle/joint pain and fev symptomatic and supportive Iron Sucrose (Venofer) [Iron Supplement] Uses Fe deficiency anemia w/ chronic HD in those receiving erythropoietin Actions Fe r lacement. Dose 5 mL (100 mg) IV on dialysis, 1 mL (20 mg)/min max Caution [C, M] Contra Anemia w/o Fe deficiency Disp Inj SE Anaphylaxis, -1- BP, cramps, N/V/D, HA Interactions i Absorption OF oral Fe supls EMS See Iron Dextran OD See Iron Dextran... 

Lastly, the positions of hydrogen atoms have been located in a series of low-surface-area aluminium oxide-hydroxides. Hence, the long known solid-state structures of diaspore (a-AlOOH) and boehmite (y-AlOOH) have been recently probed using H CRAMPS [45] along with X-ray and neutron diffraction techniques [46]. For diaspore results point to the presence of Alaf/Xa-OH) groups with 6-fold and 4-fold coordination at aluminium and oxygen, respectively, while Al2(/x-OH) moieties with 6-coordinate aluminium and 3-coordinate oxygen are revealed in boehmite [46]. 

In general, multiple pulse techniques sufficiently average the dipolar interactions, compress the chemical shift scale, but they do not affect heteronuclear dipolar interactions and the chemical shift anisotropy. A combination of both multiple pulse techniques and magic angle spinning, so-called CRAMPS (Combined Rotational And Multiple Pulse Spectroscopy) is found to yield satisfactory results in the solid state H NMR of solids 186). The limitations of all these techniques, from the analytical point of view, arises from the relatively small chemical shift range (about 10 ppm) as compared with some other frequently studied nuclei. However, high resolution H NMR of solids is useful in studies of molecular dynamics. 

Besides 29Si-NMR, that distinguishes between siloxane bridges, single and double silanols, especially H-NMR-CRAMPS (Combined Rotation and Multiple Pulse Spectroscopy) is a very powerful tool. This technique allows to differentiate the Si-OH and (after hydrolysis) the Ti-OH species, yielding thereby useful information on the structure of the surface groups3. Due to spectral overlap, this distinction is very difficult to observe by infrared spectroscopy. 

Two recent studies have examined the NMR spectra of coal macerals and lithotypes respectively. Retcofsky and VanderHardt (12) reported the aromaticities of the vitrinite, exinite, micrinite, and fusinite from Hershaw hvAb coal using non-spinning cross-polarization techniques. The fa values of 0.85, 0.66, 0.85, and 0.93 -0.96 for these macerals demonstrate clear variations between the materials at a given rank. Gerstein et. al. (13) used carbon-13 CP/MAS proton combined rotation and multiple pulse spectroscopy (CRAMPS) to examine Iowa vitrain (Star coal) and a Virginia vitrain (Pocahontas 4 coal) with aromaticities of 0.71 and 0.86 respectively. 

CRAMPS NMR [138]. The differences in the intermolecular distances of the carboxylic acid groups involved in different types of hydrogen bonding have been visualised using ODESSA (one-dimensional exchange spectroscopy by sideband alteration) and 2D EXSY (exchange spectroscopy). The ODESSA technique [139] can measure internuclear distances (up to 9 A) between chemically equivalent nuclei with the same isotropic chemical shift. Potential applications of this approach are widespread. 

Combined Rotation and Multiple Pulse Spectroscopy (CRAMPS) is a technique in which the dipolar interaction is averaged through a multiple-pulse sequence [54, 55]. The simultaneous spinning around the magic angle, as in MAS NMR, averages the chemical shift anisotropy. Under appropriate conditions, CRAMP spectra can be of greater resolution than MAS NMR spectra. While CRAMPS is not exclusively a surface-sensitive technique, the majority of catalytic applications have focused on the study of adsorbed species, and the information on surface structure that can be extracted from their spectra. 

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