A white paper written by Exeter Analytical describes how CHN microanalysis provides a powerful and straightforward method for determining whether a sample is pure - a key aspect of sample characterisation.
The paper discuss how by providing a precise and accurate analysis of the percentage Carbon, Hydrogen and Nitrogen in an organic sample - CHN microanalysis can compliment techniques such as Mass Spectrometry (MS) and Nuclear Magnetic Resonance (NMR) Spectrometry, thus enhancing the reliability of your analytical results.
Many organisations today benefit from the relative ease with which NMR can be used to determine target compound validity or elucidate the structure of an unknown in the absence of crystal data. Similarly Mass spectrometry is a powerful analytical technique used by many laboratories to identify unknown compounds, quantify known materials, and elucidate the molecular structure and chemical composition of organic and inorganic substances.
However both NMR and MS techniques have limitations when it comes to assessing sample purity. If the impurity in the sample is inorganic (e.g. silica from sample purification by flash chromatography using an acidified mobile phase) then it will be invisible to traditional 1H, 13C or 15N NMR techniques. Likewise organic contaminants present at less than c. 1% of the sample are typically invisible to NMR. Data is provided showing how CHN analysis can help determine low levels of impurities. Further data is provided showing how CHN microanalysis can be used to determine the presence of residual solvent in samples at levels that has little or no effect on the Mass or NMR spectra.