The integral of the peak associated with the reference sample is used to calibrate the instrument response. One or more peaks associated with the sample of interest are then used to determine the sample concentration or purity. Sample = designates the sample of interest.N = Normalisation factor (the number of nuclei represented by the peak).The purity can be calculated with the following equation. When quantitative methods are validated there are standard requirements for accuracy, precision, range, and linearity over that range. Table 1 below shows general requirements for a Category I NMR method when measuring a drug substance (there are other specifications for finished products and impurities). These requirements were tested by measuring the purity of one reference standard, methylsulfonylmethane (MSM), with another, maleic acid. Maleic acid is a common reference standard so this was used as the reference to measure the known purity of MSM (99.5%). A spectrum of the mixture in D 2O is shown in Figure 3. The knowledge of the assay of a substance is crucial information and of interest in many applications. For example in pharmaceutical or chemical laboratories, in the production of reference materials, or to follow the conversion of reagents in reactors. In the past decades quantitative nuclear magnetic resonance spectroscopy (qNMR) has been established as a standard method for assay determination, as it takes advantage of the fact that NMR provides a linear signal response. This results in the NMR signal intensity being proportional to the number of nuclei, which allows for an easy one-point calibration against a known standard. The type of qNMR method, which we present in this blog post, utilizes an internal standard as a reference. The other method, using an external standard, will be presented in an upcoming blog post.įor optimum performance of the internal standard qNMR method it is required that the reference material has a known assay, the integrated signals are not overlapping, and that analyte and standard are sufficiently soluble in the desired solvent.

One example of this is the determination of the assay of diclofop-methyl with dimethyl sulfone as internal standard. As it can be absorbed by the soil it is important to have a reference material with known assay with which one can determine the contamination of soil sample Diclofop-methyl is a post-emergence herbicide used, for example, for wild oats and wild millets.

Sample purity mestrenova