Nuclear magnetic resonance internal standards

EHement Stable Rel. Atomic Nuclear magnetic resonance International standard Gas for... 

D2O = deutered water. HPLC = high performance liquid chromatography. IS = internal standard. MeOH = methanol. MS = mass spectrometry. NMR = nuclear magnetic resonance. PDA = photodiode array detector. TEA = triethylamine. MTBE = methyl tert-butyl ether. 

Low Resolution Nuclear Magnetic Resonance (LR-NMR) systems are routinely used for food quality assurance in laboratory settings [25]. NMR based techniques are standardized and approved by the American Oil Chemist s Society (AOCS) (AOCSd 16b-93, AOCS AK 4-95), the International Union of Pure and Applied Chemistry (IUPAC) (solid fat content, IUPAC Norm 2.150) and the International Standards Organization (ISO) (oil seeds, ISO Dis/10565, ISO CD 10632). In addition to these standardized tests, low resolution NMR is used to measure moisture content, oil content and the state (solid or liquid) of fats in food. Table 4.7.1 summarizes common food products that are analyzed by low-resolution NMR for component concentration. 

The nuclear magnetic resonance spectrum of sodium valproate as shown in Figure 3 was obtained on a Varian Associates T-60 NMR Spectrometer in deuterium oxide containing tetramethylsilane as the internal standard. The spectral peak assignments (2) are presented in Table I. 

Since the product slowly darkens on exposure to air, it should be stored under nitrogen in a refrigerator. The compound solidifies on cooling m.p. 16.0-16.5°. Nuclear magnetic resonance spectrum (neat, tetramethylsilane internal standard) singlets at d 7.00 (aromatic protons), 3.93 (CH2), and 2.24 p.p.m. (NH). 

A nuclear magnetic resonance method for chlorpromazine has been reported [178]. For tablets, capsules, and bulk chemical, the sample is shaken with CHCI3 containing cyclohexane or piperanol as an internal standard. For injectable solutions, tetramethylammonium bromide was used as the internal standard. The NMR spectrum was recorded between 0 and 7.0 ppm, and the drug resonance at 2.7 ppm (relative to TMS) measured. The signals for the respective internal standards were at 1.5, 6.0, and 3.3 ppm. 

Figure 5. H nuclear magnetic resonance spectrum of procaine (TMS used as the internal standard).

A single measurement of a calibration sample can give the concentration of the test solution by a simple ratio. This is often done in techniques where a calibration internal standard can be measured simultaneously (within one spectrum or chromatogram) with the analyte and the system is sufficiently well behaved for the proportionality to be maintained. Examples are in quantitative nuclear magnetic resonance with an internal proton standard added to the test solution, or in isotope dilution mass spectrometry where an isotope standard gives the reference signal. For instrument responses As and /sample for internal standard and sample, respectively, and if the concentration of the internal standard is Cjs, then... 

All NMR spectra were recorded on a Varian A-60 spectrometer at room temperature by Nuclear Magnetic Resonance Specialties, Inc., New Kensington, Pa. Benzene soluble fractions were recorded in deuterated chloroform solution (CDCls) while dimethyl sulfoxide-dc (DMSO-dr.) was the solvent employed for other fractions. (Deuterated chloroform with enrichment of 99.8% was purchased from Bio-Rad Laboratories and dimethyl sulfoxide-dr, with enrichment of 99.6% from Merck, Sharp, and Dohme of Canada.) The internal standard used with the CDCla solutions was tetramethvlsilane and hexamethyl-disiloxane (chemical shift 7 c.p.s.) with DMSO-d . Prior to preparation for NMR recording, the samples were thoroughly dried in a vacuum at 110°C. The NMR tubes were sealed to minimize the absorption of atmospheric moisture. The chemical shifts given in c.p.s. are referred to tetramethylsilane. 

International Standard Organization (ISO) 10565. 1999. Oilseeds-Simultaneous Determination of Oil and Moisture Contents - Method Using Pulsed Nuclear Magnetic Resonance Spectrometry. International Organization for Standardization, Geneva. 

H NMR spectrum The proton nuclear magnetic resonance (1H NMR) spectrum of omeprazole were 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 DMSO-d6 and all resonance bands were referenced to tetramethylsilane (TMS) as internal standard. The H NMR spectra of omeprazole are shown in Figs. 4.9-4.12 and the COSY H NMR is... 

A 400 MHz nuclear magnetic resonance (NMR) method for the identification of rocuronium bromide was reported by Fielding [10]. The aH spectra were referenced to an internal TMS standard, while the solvent signals at 77.0 ppm (CDCI3) or 39.6 ppm (DMSO-dg) were used as references for the 13C data. Based on the NMR spectra, it was concluded that... 

Nuclear magnetic resonance (NMR) spectrometry [4] Both the 1H NMR and 13C NMR spectra of zaleplon have been obtained in DMSO- as a solvent and using tetramethylsilane as the internal standard (IS). The assignments for both the 1H and 13C NMR spectra make use of the following numbering scheme ... 

Where the result does not depend on such factors, or a normalisation to an internal standard is carried out by the spectrometer or accompanying software automatically (e.g. in Nuclear Magnetic Resonance - NMR), further normalisation should not be carried out. 

Fig. 1. —Nuclear Magnetic Resonance Spectrum of lA3,4-Tetra-0-acetyl-5-[(ben-zyloxycarbonyI)amino]-5-deoxy-a-D-xylopyranose (207). (Taken at 100 MHz in chloroform at 35° acetyl protons omitted the decoupled signals are indicated above tetra-methylsilane as internal standard.)...

Thorn K. A., Folan D. W., and MacCarthy P. (1992) Characterization of the International Humic Substances Society Standard and Reference Fulvic Acids by Solution State Carbon-13 and Hydrogen-1 Nuclear Magnetic Resonance Spectrometry. Water Resources Investigations Report 89-4196, U.S.G.S. Denver, 93pp. 

Thom, K.A. Folan, D.W. MacCarthy, P. Characterization of the international humic substances society standard and reference fulvic and humic acids by solution state carbon-13 O C) and hydrogen-1 OH) nuclear magnetic resonance spectroscopy , U.S. Geological Survey, Water Resource Investigations Report, Denver, Co, 1989 89-4196, pp. 1-4. 

Nuclear magnetic resonance (- -H NMR) spectra were recorded on either a Varian T-60 or a Varian FT-80A with Me Si as an internal standard. Infrared spectra were obtained on a Perkin-Elmer 735B infrared spectrophotometer. All boiling points and melting points are uncorrected. Thin layer chromatography (TLC) utilized silica gel 60 F-254 chromatoplates (0.2-5 mm thickness). 

Instruments Batch experiments for obtaining CL profiles were performed using a Microtec NITI-ON Lumicounter 2500 (Chiba, Japan). Proton nuclear magnetic resonance ( H-NMR) spectra were obtained on a JEOL JNM-EX270 spectrometer (Tokyo, Japan) with tetramethylsilane as an internal standard. Mass spectra (FAB-MS) were measured on a JEOL JMS-LXIOOO (Tokyo, Japan) with w-nitrobenzyl alcohol as a matrix. 

The field of application for the isotope dilution method with radioactive tags, extends to measurements using stable isotope. Mass spectrometry or nuclear magnetic resonance are used to determine the variations in the isotopic concentrations. Chemical labelling using externally introduced tags consists of the addition to a sample of the same analyte but containing a stable isotope (e.g. H, C, N) as an internal standard. This method is as much used for molecular species as for atoms (around 60 have stable isotopes). 

The nuclear magnetic resonance (NMR) spectra were recorded on a Varian A-60 spectrometer, using deuterated dimethyl sulfoxide (DMSO) as solvent and tetramethylsilane as internal standard. IR spectra were obtained on a Perkin-Elmer 237B IR spectrophotometer. 

The last method to be presented for the analysis of the carbon-bonded fluorine in fluorouracil is F Nuclear Magnetic Resonance spectrometry (3). A fluorouracil reference standard and an internal standard. 

A) Schematic diagram of a simple nuclear magnetic resonance (NMR) spectrometer. The sample is placed in solution in a long, thin tube and spins in a probe sitting in a magnetic and surrounded by radio-frequency (RF) coils B) proton NMR spectrum of ethanol (QH O) with tetramethylsilane (TMS) added as internal standard. On the 8-scale of chemical shifts,... 

Melting points were measured in open capillary tubes in a Scientific Glass Co. melting point apparatus. Melting points and boiling points are uncorrected. The nuclear magnetic resonance spectral data presented were obtained with a Varian model T-60 spectrophotometer using dimethylsulfoxide or tetramethylsilane as an internal standard. A Perkin-Elmer Model 137 Sodium Chloride spectrophotometer was used to record infrared spectra. 

The sample was prepared by the neat technique on KBr plate or by the KBr pellet technique. The proton nuclear magnetic resonance (NMR) spectra were obtained at 60 MHz with a JEOL-PMX 60 spectrometer. Deuterochloro-form and carbon tetrachloride were used as solvents with tetramethyl-silane (TMS) as the internal reference standard. The X-ray diffraction patterns of the powdered samples were taken in the region of 5 to 3 o by a Rigakudenki Model DC-8 X-ray diffractometer, using Ni-filtered Cu-Ka radiation. 

As with the convention for proton nuclear magnetic resonance, the cmr shifts are reported in parts per million (ppm) downfield from standard tetra-methylsilane (TMS). If the chemical shifts were originally reported relative to some other internal standard, these values were converted to a TMS reference for uniformity and ease of comparison. The equation used was Stms = cDcig + 77.0 = 192.4 - Scss = + 6.9. Deuteriochloroform... 

Fio. 4. Nuclear magnetic resonance spectrum taken in CCU solution with benzene as internal standard at a radiofrequency of 25 megacycles. The chemical shifts are given in cycles per second. 

H and C NMR spectra were recorded with a 300 MHz or 500 MHz spectrometer. Chemical shifts are reported in parts per million (ppm) relative to tetramethylsi-lane (TMS) as the internal standard. Nuclear magnetic resonance (NMR) data are... 

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