Web Release Date: March 26,
Quantitative 1H NMR with External Standards: Use in Preparation of Calibration Solutions for Algal Toxins and Other Natural Products
Institute for Marine Biosciences, National Research Council of Canada, 1411 Oxford Street, Halifax N.S., Canada B3H 3Z1
Received for review November 1, 2004. Accepted February 22, 2005.
Abstract:
We examine the use of external standards for quantitative
measurement by 1H NMR of solution concentrations of
natural products and other low molecular weight, hydrogen-containing compounds and show that precision and
accuracy ca. 1% is obtainable with a commercial 11.7 T
spectrometer when standards and analytes are contained
in separate but identical sealed precision glass NMR
tubes. Numerous factors contributing to the intensity of
the NMR signals are evaluated. Precise measurements of
360
pulse lengths for each sample provide direct corrections for variations in probe Q-factor that enable
samples in different solvents to be compared, provided
single-coil excitation and detection is used throughout.
Samples need not be prepared in deuterated solvents if
the 1H spectra of the solvents are simple enough for peak
suppression by presaturation. The approach is particularly suitable for hazardous materials kept in sealed tubes
and for the preparation of certified calibration solution
reference materials for use with LC-MS and other techniques where deuterated solvents should be avoided.
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