ISO_NWIPs-for-Ballot

ISO/NP

e) Data processor equipment, to apply Fourier transformation to digitized the FID signals and convert 531 them to NMR spectra, to display, analyse and save them to recording devices; The signal processing 532 may be performed using software algorithms embedded in the spectrometer, or offline using 533 bespoke, specialist software. 534 f) Optional devices such as 535 auto-sample changer, which can automatically exchange the NMR tubes, 536 auto-tuning device, to perform automatic tuning of the electric circuits for the NMR probe and 537 sample each time the sample is exchanged, 538 temperature control device, to control the temperature of the sample being measured. 6.1 General 542 For 1 H qNMR, there are two methods: an internal standard method and an external standard method. 543 With the internal standard method, a small amount of a reference material for qNMR and the analyte 544 are dissolved together in a solvent, and the solution is placed into an NMR tube to perform 545 measurements. Using this method, the signals from the analyte and a reference material for qNMR are 546 measured under the same conditions. 547 In contrast, for the external standard method, a solution of the analyte dissolved in a solvent is prepared 548 separately from the solution of the reference material for qNMR dissolved in a solvent. Each of the 549 solutions is placed in a separate NMR tube. Since the measurement results for the sample solution and 550 the solution of a reference material for qNMR are not obtained in exactly the same environment, they 551 will have inherently larger associated uncertainties compared with results obtained by the internal 552 standard approach 553 Therefore, for 1 H qNMR use of an internal standard method is recommended when accurate and 554 precise results are required. However, in cases where measurements are difficult using the internal 555 standard method and an external standard method must be used, verification is performed using a 556 substance of known concentration to confirm that the target accuracy is achieved with the 557 measurement method, or some other outside verification of the accuracy of the external standard 558 method is carried out [see ref. 15]. 559 In order to obtain good quality spectra, it is necessary to prevent any suspended solids from being 560 introduced into the solution, such as solid impurities, dust, etc. The presence of such solids can cause 561 shimming errors (line width of the signals become wider and asymmetry of peaks), leading to a 562 decrease in quality of spectra. 563 It is also important to have a homogeneous concentration of the solution. Particularly with high 564 magnetic field apparatus, the signal resolution is adversely influenced by inhomogeneity of the solution 565 concentration. In addition, if the concentration is too high, the viscosity increases and actually broadens 566 resonances. 567 There are various types of NMR tubes. Typically, small diameter NMR tubes ( ≦ 5 mm) are used, and 568 with a local magnetic field with good uniformity, good quality spectra with excellent resolution can be 569 obtained. To obtain spectra with high resolution, as the magnetic field becomes higher, it is necessary to 570 539 540 541 6 Preparation for 1 H qNMR

© ISO 2017 – All rights reserved

20