Natural Isotope Abundance

Isotope Natural abundance (%) Nuclear spin Electric quadrupole moment NMR frequency fora 23.5 kO field (MHz) Relative sensitivity... [Pg.12]

Atom Isotope Natural abundance Monoisotopic Average mass mass ... [Pg.355]

Isotope Natural Abundance (% total carbon) Remarks... [Pg.299]

In the case of pharmaceutical solids that are dominated by carbon and proton nuclei, the dipole-dipole interactions may be simplified. The carbon and proton nuclei may be perceived as dilute and abundant based upon then-isotopic natural abundance, respectively (Table 1). Homonuclear 13C—13C dipolar interactions essentially do not exist because of the low concentration of 13C nuclei (natural abundance of 1.1%). On the other hand, H—13C dipolar interactions contribute significantly to the broad resonances, but this heteronuclear interaction may be removed through simple high-power proton decoupling fields, similar to solution-phase techniques. [Pg.98]

NMR active isotope Natural abundance Gyromagnetic ratio y fH = 100) Corresponding NMR inactive" isotope Natural abundance Gyromagnetic ratio y ( H=T00)... [Pg.374]

Element Isotope Natural abundance (%) or half-life Standard isotope ratio or energy... [Pg.216]

Polyatomic Ion Interfered Isotope (Natural Abundance %) Required Resolution... [Pg.470]

Make a preliminary estimate of the intensity for each element, based on isotopic natural abundances. [Pg.123]

Although several other important nuclides can be detected by NMR, proton ( H) remains the most widely used because of its high sensitivity, high isotopic natural abundance (99.985%), and ubiquitous presence in organic compounds. Of comparable importance is carbon ( C), 1.108% abundance, which, because of substantial improvements in instrument sensitivity, is now utilized as routinely as proton. Fluorine ( F), 100% abundance, is less used since it is present in only about 10% of pharmaceutical compounds. Another consequence of the intrinsic low sensitivity of NMR is that virtually all samples require signal averaging to reach an acceptable signal-to-noise level. Depend-... [Pg.906]

The technique of stable Isotope dilution permits one to determine very accurately the trace element content of a particular sample as well as using stable Isotopes as metabolic tracers The concept of Isotope dilution for trace element determinations Is both simple and elegant A known quantity of an enriched stable Isotope Is added to the sample to be analyzed By measuring the amount of that Isotope (added) relative to another Isotope (not added) of the element, one can easily calculate the amount of analyte present originally In the sample Thus, the normal relative amounts of the two Isotopes (natural abundance) have been altered, or "diluted" ... [Pg.92]

T. Preston (1992) The measurement of stable isotope natural abundance variations. Plant Cell Environ. 15, 1091-1097... [Pg.653]

Element Atomic Weight (amu) Isotope % Natural Abundance Mass (amu)... [Pg.190]

The multiple-quantum (MQ)/MAS NMR is one of the 2D NMR methods, which is capable of averaging out the second-order quadrupolar interaction in nuclei with spin > 1/2 such as H, "B, O, etc. The "B MQ/ MAS NMR measurements on boron as contained in silyl-carborane hybrid Si-based polymer networks considered here. The molded samples are cut into small pieces to insert them into a 4-mm NMR rotor and spun at 12 kHz in a MAS probe. The observation frequency of the "B nucleus (spin number I = 3/2 and isotope natural abundance = 80.42%) is 96.3 MHz. Excitation of both the echo (—3Q) and anti echo (+3Q) coherences is achieved by using a three-pulse sequence with a zero quantum filter (z-filter). The widths of the first, second, and third pulses are 3.0 4.1 ps, 1.1-1.6 ps, and 19-28 ps, respectively. The z-filter is 20 ps. The recycle delay time is 6-15 s and the data point of FI (vertical) axis is 64 and for each the number of scans is 144. Then, the total measurement time is 15-38 h. The phase cycling used in this experiment consists of 12 phases. Boron phosphate (BPO4 3 = 0 ppm) is used as an external standard for "B. The chemical shift value of BPO4 is —3.60 ppm from BF3 O(C2H5)2 which is used as a standard reference in " B NMR in the liquid state. The transmitter frequency of " B is set on peak of BPO4 for a trustworthy chemical shift after Fourier transform." " ... [Pg.208]

Isotope Natural abundance (%) Magnetic moment (m/Mn) Magnetogyric ratio Y (10 radT s ) NMR frequency (H, Hz)"-" Relative receptivity D( C) ... [Pg.204]

Isotope Natural abundance [%] Identifier Spin (quantum number) Relative ratio (y(n... [Pg.116]

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