Referencing spectra external

Figure 7. 31P-CP/MAS solid-state spectrum of [PtCl2(PPhgCHs)t] at 36,442 MHz (a), 31P-CP/MAS solid-state spectrum of [PtCl2(PPh2CH2CH2Si(OEt)s] at 36.442 MHz (b), and 31P-CP/MAS solid-state spectrum of PtCl2[PPh2CH2CHgSi-(OEt)s] covalently immobilized on glass beads. All spectra referenced to external 85% HsPOk (18,). (Reproduced with permission from Ref. 40. Copyright 1982, Royal Society of London.)...

Figure 3. lH NMR spectrum of 14, Z-H, in S02CIF, referenced to external TMS (Reproducedfrom reference 38. Copyright 2006 American Chemical Society.)... 

Figure 4 Detail of the amide carbonyl resonances in the C-NMR spectrum (100 MHz) of poly (Lys-25) in 70% H2O/30% D2O solution. The spectrum was recorded on a Varian INOVA 400 NMR spectrometer. Chemical shifts were referenced to external tetramethylsilane.

Dicarbaundecaborane(13) is a white hygroscopic solid which is soluble in water, alcohols, and aromatic solvents. It is best stored cold in a dry, inert atmosphere. The proton-decoupled nB NMR spectrum (115 MHz, C6D6, referenced to external BF3OEt2) shows peaks at d 4.0 (2 B), - 4.4 (2 B), - 16.4 (1 B), - 17.0 (1 B), and - 27.4 (3 B). The complex is a diprotic acid with pK i of 2.98 and pKa2 of 14.25.6 Deprotonation of C2B9H13 with butyl lithium in benzene affords anhydrous Li2C2B9Hi... 

FIGURE 6.2 Top, the proton-decoupled 15N (30.4 MHz) NMR spectrum of formamide in CDC13 referenced to external NH3. Second, the proton-decoupled 15N NMR spectrum (30.4 MHz) of ethylenediamine in CDC13. The proton-coupled spectrum is shown in the inset. Third, the proton-decoupled 15N spectrum (30.4 MHz) of pyridine in CDC1> Fourth, the proton-decoupled 15N (30.4 MHz) spectrum of quinine in CDC13. 

The proton nuclear magnetic resonance spectrum of lomefloxacin mesylate obtained in D2O at 25° C is given in Figure 5 (9). The spectrum was obtained on a Bruker AM-500 NMR Spectrometer operating at 500.13 MHz and was referenced to external TSP [3-(trimethylsilyl)propionic-2,2,3,3-d4 acid]. The chemical shifts and spectral assignments are provided in Table 2 (9,10). The effect of increasing concentrations of Al3+ on the... 

Figure 2.39. The B NMR spectrum (128 MHz) of dansylamidophenylboronic acid 2.5 (a) as the free trigonal boronic acid (Avi/j 580 Hz) and (b) as the tetrahedral complex with the active site serine of the P99 f)-lactamase from Enterobacter cloacae (Avi/j 160 Hz). Spectra are referenced to external trimethylborate (adapted with permission from [11]).

Figure 6.11. A gradient-selected HSQC spectrum of the carbopeptoid 6.3 at natural N abundance plotted at high and at low contour levels to show the thermal noise floor. No ti-noise artefacts remain from the parent resonances ( N is referenced to external liquid ammonia).

FIGURE 7.1. The proton-decoupled 15N (30.4-MHz) NMR spectrum of formamide in CDC13 referenced to external NH3. 

It is technically possible, but very difficult, to measure the exact frequency of a radio signal, and in practice the frequency of the energy absorbed by a test compound (usually called the resonance frequency) is measured relative to that of a reference compound. This reference may be mixed with the sample (direct referencing), or if contamination of the sample is undesirable it may be placed in a separate container within the sample tube (external referencing). In proton and 13C NMR, the reference compound usually used is TMS (tetra-methyl silane) or its water-soluble derivative DSS (2,2-dimethylsilapentane 5-sulphonic acid). These compounds give a sharp proton peak at the right-hand side of a typical NMR spectrum (Figure 2.39). 

The NMR spectra of adsorbed xenon were obtained on a Bruker MSL-300 spectrometer operating at 83.0 MHZ and 295K. Typically, 2000-40000 signal acquisitions were accumulated for each spectrum with a recycle delay of 0.3s between 90 pulses. The Xe NMR chemical shifts were referenced to that of external xenon gas extrapolated to zero pressure using Jameson s equation [11]. All resonance signals of xenon adsorbed in zeolites were shifted downfield from the reference but were taken to be positive in this report. 

FIGURE 43. 29Si NMR MAS spectrum of Si50(PC>4)6. The chemical shift is referenced to the M signal of the Q8M8 external standard (+11.5 ppm). Delay between 30 ° pulses is 20 s, number of scans is 2242 and the frequency is 39.74 MHz. Reproduced by permission of Elsevier Science from Reference 147... 

Upon initial installation using the hardware approach of Fig. 44, the probe-head-injected intensity calibration path must be referenced against the ideal external calibration protocol to account for the probe optic s contribution to the measured spectrum. This is validated in all cases, as the probe optic is spectrally stable (unless fouled), and if this is anticipated, antifouling methods should be employed. The probe-head-injected neon wavelength calibration path is optically equivalent to the ideal external neon path for purposes of wavelength calibration being fed to the analyzer through the same optical fiber. Some industrial installations allocate one of the channels of a multichannel system, as shown in Fig. 45, to a sample compartment. This sample compartment can be used to either contain a permanent Raman standard, such as a sample of cyclohexane, or to run standard samples to improve or validate a calibration model. 

The 282.3 MHz F spectrum for FPAE 2 prepared using a 3% molar excess of decafiuorobiphenyl was recorded. The peaks in the spectrum were referenced externally to a,a,a-trifluorotoluene at -63.7 ppm. The spectrum is dominated by the peaks centered at -139.0 and -153.7 ppm corresponding to the F2 and FI fluorine atoms, respectively, in FPAE 2 (Scheme 1). These assignments were confirmed by examining the F spectrum of the model compound, 4,4 -diphene... 

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