ISO_NWIPs-for-Ballot

ISO/NP

R is the chemical shift of the reference nuclei (δ R is zero for TMS). 330 Chemical shifts are normally expressed in parts per million (ppm). The signal position has to be defined 331 with the signal position of the reference compound (reference nucleus). 332 The magnetic field acting on the nuclei in a molecule is not only affected by the surrounding electrons 333 (nuclear shielding), there is also influence from other magnetic nuclei within the molecule (nuclei that 334 have nuclear spin are one such type of magnet themselves). This results in a splitting of the signal due 335 to coupling through the chemical bonds between the nuclear magnets. The total area of the split signals 336 is unchanged, and the method is still quantitative. 337 In first order spectra the spacing between two adjacent components of a split signal is known as the 338 spin-spin coupling constant ( J) . However, in higher order spectra this spacing does not represent the 339 actual J -coupling anymore. Accurate values for J can then be obtained only by a quantum mechanical 340 spectral analysis. J is measured in Hertz (Hz), and is independent of the strength of the external 341 magnetic field. As the number of nuclei that interact with each other increases, the splitting pattern 342 becomes more complex. 343 From the NMR spectrum, the following information can be obtained: chemical shift, spin-spin coupling 344 constant, and signal intensity so on. The information can be used to identify and analyse the structure of 345 a chemical substance, as well as for quantification. 346 Note: The relaxation time cannot necessarily be obtained from every spectrum, so three parameters are typically 347 obtained. The coupling constants are represented in spectra; however, it is sometimes difficult to determine them 348 directly, but peak shape is chemical shift. The intensities of 1 H are also susceptible to relaxation: If a short delay 349 between pulses is used, then 1 H intensities will be affected. The difference is due to 13C's typically longer 350 relaxation times, which requires a much longer delay between pulses for over 99% recovery. 351 One-dimensional 1 H NMR is characterized by the fact that the ratio of the numbers of nuclei in a 352 compound corresponds to the ratio of the signal areas observed on a spectrum when the measurements 353 are made under conditions that ensure the quantitative performance. Furthermore, when one- 354 dimensional 1 H NMR is performed under conditions that ensure quantitative performance, and a 355 reference standard material for qNMR that satisfies the requirements for International System of Units 356 (SI) traceability and has the property that the ratio of the numbers of nuclei in the compound observed 357 on the spectrum corresponds to the signal ratio is used, it is possible to obtain highly-reliable values for 358 the purity and content based on the amount of material (mol). This kind of measurement technique is 359 called 1 H qNMR. 360 4.2 1 H quantitative NMR ( 1 H qNMR) 361 The spectra obtained by proton nuclear magnetic resonance ( 1 H NMR) spectroscopy on a substance 362 dissolved in a solvent have the characteristics described below. These characteristics are utilized to 363 perform analysis of chemical structures. 364 The resonance signals have different chemical shifts that depend on the chemical structure of the 365 analyte. 366 The signals are split by spin-spin interactions arising from the number of 1 H bonded to the adjacent 367 carbon atoms. 368 The signal intensities (areas) are proportional to the number of 1 H resonating at each frequency. 369

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