Instrumental techniques such as NMR and Mass Spectroscopy are routinely used to elucidate the structures of organic materials, but all have their limitations, particularly when it comes to contamination from inorganic species.
It is therefore essential to use a range of methods when fully characterising a sample, of which CHN analysis forms a part.
CHN Analysis
The determination of Carbon, Hydrogen and Nitrogen can play a very important role in the various processes of synthesis, separation, purification and the structural identification of organic compounds, both for research and quality control purposes.
CHN analysers provide a quick cost-effective method to check sample purity and to determine the empirical formula of new carbon-based compounds.
Sulphur and Halogen Analysis
In many organic materials, it is also necessary to analyse for Sulfur or Halogen atoms. Analysis of these elements usually relies on combusting the material in an Oxygen-rich atmosphere, the products of the combustion being absorbed in an aqueous-based solution. A variety of techniques can then be used to determine the Sulfur or Halogen content.
These techniques include:
- Classical Potentiometric Titrations
- Ion Chromatography
- ICP
Butterworth has been using Ion Chromatography for the analysis of Fluorine, Chlorine, Bromine and Iodine since its introduction in the late 1970s, to negate the problems of co-precipitation associated with titrimetric analysis.
Metals Analysis
The determination of metals in pharmaceutical samples, where they are active components is of particular importance. Oxygen combustion can be used, as a preparation technique metals such as Phosphorus. However, a more accurate method is by Closed Vessel Microwave Digestion followed by ICP or AAS, the advantages of which include:
- Automated digestion procedure allowing multiple sample preparations
- Accurate matrix matching
The use of either ICP-OES or ICP-MS enables the analyst to select the optimum Wavelength/Mass Number for any element to prevent interference from other components present in the sample matrix.