ISO_NWIPs-for-Ballot

ISO/NP

b) Preferably specify the amounts of sample and reference material for qNMR to be weighed out, such 731 that they give signal areas with as nearly equivalent levels as possible. 732 c) To prepare the sample solution, add an appropriate volume of deuterated solvent to the vessel 733 containing the sample and the reference material for qNMR in order to dissolve them. 734 d) Place a suitable volume of the prepared sample solution into an NMR tube for measurement. 735 736 6.9 Measurement conditions for 1 H qNMR 737 Depending on the NMR apparatus used, the settings for parameters such as the target nucleus for 738 measurement, digital resolution, observed spectrum region, spinning, pulse flip angle, 13 C decoupling, 739 repetition time, number of transients, dummy scan, temperature, etc. are usually set to conditions that 740 are suitable for quantitative analysis, as shown below. For accurate quantitative analysis, signal 741 separation and an adequate signal-to-noise ratio (SNR) are required [see ref. 18]. 742 When using both analyte and qNMR reference materials for qNMR for which the purity is assured, such 743 as Certified Reference Materials (CRMs), if purity measurements of the analyte are performed and it is 744 confirmed that the target quantitative accuracy is obtained, it is acceptable to change the parameter 745 settings. However, if specified measurement conditions for 1 H qNMR are given in separate standards, 746 those should be followed. 747 Furthermore, to ensure quantitative accuracy to two significant digits or more when measuring the 748 purity of low molecular weight organic compounds, the following conditions a) to j) are recommended 749 for the default settings [see ref. 11]: 750 a) NMR apparatus: nuclear magnetic resonance spectrometer with a proton ( 1 H) resonance 751 frequency of ≥300 MHz; 752 b) Digital resolution: less than or equal to 0,25 Hz; 753 c) Observation spectrum region : approximately double the value of chemical shift of the signal peak 754 analysed; 755 d) Spinning: OFF; 756 e) Pulse flip angle: 90°; 757 If a repetition time that satisfies the conditions for accurate quantification is ensured (at least 7 758 times longer than T 1 ), a pulse flip angle of 90° is recommended in order to make it possible to obtain 759 the highest SNR per unit time. However, if signals are observed over a wide range, decreasing the 760 pulse angle can suppress the decrease in excitation efficiency for signals that are separated from the 761 excitation centre, so it is worthwhile to try a smaller pulse flip angle in this case. 762 f) 13 C decoupling: depending on the sample; 763 g) Repetition time delay: spin-lattice relaxation time T 1 multiplied by a factor of 7 or more; 764

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