ISO_NWIPs-for-Ballot

ISO/NP

When NMR is used for structural analysis, the detection sensitivity if a priority, so SNR is improved 398 by increasing the number of transients without using an adequately long repetition time. As a result, 399 the ratio of the signal areas to the numbers of 1 H within the molecule is no longer consistently the same. 400 However, under conditions that ensure a quantitative performance, the ratio between the signal areas 401 for resonance signals i and j, showing different chemical shifts within the same molecule, is described 402 by Formula (5). 403 404 where 405 S i is the signal area (intensity) of resonance signal i in the molecule; 406 N i is the number of protons corresponding to resonance signal i in the molecule; 407 S j is the signal area (intensity) of resonance signal j in the molecule; 408 N j is the number of protons corresponding to resonance signal j in the molecule. 409 This quantification relationship can also be applied to the signals derived from two different molecules 410 within the same measurement system. This is because k (Formula 5) applies to all compounds in the 411 sample. 412 In this case, it is assumed that when a sample solution is measured, the excitation pulse angle and the 413 volume of the solution are constant, and do not depend on the target analyte. In such a case, from 414 Formulae (4) and (5), the following Formulae (6), (7) and (8) can be obtained, in which the observed 415 signal area S is proportional to values that depend only on the compound being measured, such as the 416 mass m , molear mass M , and content or purity P of the analyte. 417 j i j i N N S S (5)

S S

k k

N N

c c

418 419

(6) (7) (8)

a

a

a

s

s

s

a S S c N N

c

s

a

s

s

a

© ISO 2017 – All rights reserved 420 421 where 422 P a is the content or purity of the analyte; 423 P s is the purity of the reference material for qNMR; 424 S a is the signal area of the analyte; 425 S s is the signal area of the reference material for qNMR; 426 s P a s s a a s s a S S P a m m M M N N

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