Purity assessment problem in quantitative NMR—impurity resonance overlaps with monitor signal multiplets from stereoisomers
- 28 April 2006
- journal article
- research article
- Published by Springer Science and Business Media LLC in Analytical and Bioanalytical Chemistry
- Vol. 385 (4), 760-765
- https://doi.org/10.1007/s00216-006-0415-4
Abstract
This paper describes the situation that can emerge when the signals to be evaluated in quantitative NMR measurements—so-called “monitor signals”—consist of several resonance lines from the stereoisomers of the analyte in addition to an impurity signal underneath. The monitor signal problem is demonstrated in the purity assessment of two samples of 2-(isopropylamino)-4-(ethylamino)-6-chloro-1,3,5-triazine (atrazine), a common herbizide which served as analyte in a CCQM intercomparison. It is shown that, in DMSO-d6 solution, a mixture of stereoisomers leads to several individual overlapping singlets, which are further split by spin–spin coupling. A measurement protocol was developed for finding and identifying an impurity that has a signal that is positioned precisely beneath the methyl signal chosen as the monitor signal in one of the samples. Quantitative NMR purity assessment is still possible in this special case, but with higher uncertainty.Keywords
This publication has 6 references indexed in Scilit:
- Structure analytical methods for quantitative reference applicationsAccreditation and Quality Assurance, 2005
- Validation of quantitative NMRJournal of Pharmaceutical and Biomedical Analysis, 2005
- An uncertainty budget for the determination of the purity of glyphosate by quantitative nuclear magnetic resonance (QNMR) spectroscopyAccreditation and Quality Assurance, 2004
- Primary methods for the measurement of amount of substanceMetrologia, 2001
- NMR als primäre analytische MeßmethodeNachrichten aus Chemie, Technik und Laboratorium, 1998
- NOTECatalan Review, 1998