Precision of integrals in quantitative NMR |
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| Affiliation: | 1. Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, SP, Av. Bandeirantes, 3900 Bairro Monte Alegre, CEP 14040-901 Ribeirão Preto, SP, Brazil;2. Núcleo de Pesquisas em Produtos Naturais e Sintéticos, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, s/n°, Bairro Monte Alegre, CEP 14040-903 Ribeirão Preto, SP, Brazil;1. Department of Physics, Sri Sarada College for Women (Autonomous), Salem, 16 Tamil Nadu, India;2. Department of Physics, Periyar University, Salem, 16 Tamil Nadu, India;1. Department of Inorganic Chemistry and Technology, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia;2. Department of Physical and Organic Chemistry, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia;3. Jožef Stefan International Postgraduate School, Jamova 39, 1000 Ljubljana, Slovenia;1. Department of Chemistry, College of Science, King Faisal University, P.O. Box 380 Al Hofuf, Al Ahsa 31982, Saudi Arabia;2. Chemistry Department, Faculty of Science, Sohag University, Sohag 82534, Egypt;3. Chemistry Department, Faculty of Science, Benha University, 13518 Benha, Egypt |
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| Abstract: | Quantitative applications of NMR use the integral of a line. This random variable has an expectation value (the area of interest) and a standard deviation due to incomplete noise averaging by the integration process. The presence of such fluctuations adversely affects the precision with which integrals can be determined. The autocorrelation function of the noise in the frequency domain has been computed. An expression of the standard deviation of the integral has been derived. The effect of an exponential apodization was investigated. It was found that the precision of the integral decreases roughly as the inverse square root of the integration range, and that it is hardly improved by exponential multiplication. Sine-bell apodization is also shown to be ineffective in improving precision, while zero-filling has no influence. These conclusions are validated by computer simulations. |
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