Referencing spectra internal

The proton NMR spectrum of miconazole nitrate was obtained using a Bruker Instrument operating at 300, 400, or 500 MHz. Standard Bruker Software was used to execute the recording of DEPT, COSY, and HETCOR spectra. The sample was dissolved in DMSO-d6 and all resonance bands were referenced to the tetramethyl-silane (TMS) internal standard. The 1H NMR spectra of miconazole nitrate are shown in Figs. 5-7 and the COSY 1H NMR spectrum is shown in Fig. 8. The H NMR assignments for miconazole nitrate are provided in Table 3. 

The C-NMR spectrum of diloxanide furoate was obtained using a Bruker system operating at 75, 100 or 125 MHz. The sample was dissolved in CH30H-d4, and all resonance bands were referenced to the tetramethylsilane internal standard. 

The one-dimensional l3C-NMR spectrum of pantoprazole sodium dissolved in DMSO was obtained using a Jeol 500 Lambda NMR spectrometer. The spectrum shown in Figure 8 was recorded at 24°C and internally referenced to tetramethylsilane. The assignments for the various resonance bands are found in Table 4. 

NMR spectrum The one-dimensional NMR spectrum of buclizine dissolved in CDCI3, which was recorded at 24 °C and internally referenced fo TMS. The NMR assignmenfs are presenfed in... 

Whereas the emission spectrum for Fura-2 (Figure 3.3B), which peaks at 505-510 nm, hardly shifts wavelength when Ca + is bound, the absorption spectrum shifts toward shorter wavelengths. In studies of free concentrations where internal referencing is necessary, for example, in studies of single cells, it is therefore advantageous to excite alternately at 350 and 385 nm, and to measure the ratio of fluorescence intensity at —510 nm. 

Figure 4. Proton magnetic resonance spectroscopy of the anomeric proton region of peptidophosphomannan (10). Fifty mg of peptidophosphomannan was dissolved in H20 and held at room temperature for 1 hr. The solvent was removed under reduced pressure and the residue redissolved in 1 mL H20. The NMR spectrum was taken on a Varian XL-100 MHz spectrometer at 29°C with the instrument locked on deuterium and referenced to an internal standard of sodium 2,2-dimethyl-2-silapentane-5-sulfonate.

When preparing a sample it is common practice to add a suitable compound to act as an internal chemical shift reference in the spectrum, and the selection of this must be suitable for the analyte and the solvent. In proton and carbon NMR, the reference used in organic solvents is tetramethylsilane (TMS, 0.0 ppm), which has a number of favourable properties it has a sharp 12-proton singlet resonance that falls conveniently to one end of the spectrum, and it is volatile so can be readily removed and it is chemically inert. In a few cases, this material may be unsuitable, such as in the study of silanes or cyclopropanes. For routine work, it is often not necessary to add any internal reference as the residual lines of the solvent itself can serve this purpose (Table 3.2). For aqueous solutions, the water soluble equivalent of TMS is partially deuterated sodium 3-(trimethylsilyl)propionate-d4 (TSP-dt), which is also referenced to 0.0ppm. A volatile alternative is 1,4-dioxane ( H 3.75 ppm,... 

The reference compounds recommended by the International Union of Pure and Applied Chemistry (Harris et al. 2001) are included in Table 6.1. Several of them are liquids thus, a spectrum of the reference sample is acquired and referenced prior to the study of the sample under investigation. In practise, solid compounds with well-defined structures are often used as secondary reference materials, since it may be more convenient to test the setup of the experiment on the solid sample. 

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