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Elemental analysis offers scientists a method of determining the elements present in an organic compound, and in what quantity. Various fields of science rely on this type of analysis for research, quality control, and development. Medicine, engineering, and chemistry are just a few of the fields that utilize elemental analysis of organic compounds. Here, we discuss why it is important, and detail the most common method of elemental analysis of organic compounds, CHNSO analysis.
What is Elemental Analysis and Why Carry it Out for Organic Compounds?
Elemental analysis of a compound is the process by which a sample is analyzed to determine elements present and in what quantity. Sometimes, the sample’s isotopic composition is also defined. Elemental analysis can be categorized as being qualitative, where the presence of particular elements is determined, or quantitative, where the volume of a particular element present in the example is determined.
The process can be carried out on compounds in solid, liquid, or gas. Depending on the type of methodology used, samples occasionally have to be pre-reacted by techniques such as acid digestion and combustion. Usually, sample sizes required for the elemental analysis to be successful range from just a few milligrams or less to several grams.
Elemental analysis can provide vital information about the composition of a sample. In terms of organic compounds, such as bodily fluids, chemical compounds, drinking water, minerals, soil, or waste, elemental analysis can reveal key information that can be used to inform scientists about the health of a person or an environment, the safety and quality of drinking water, and the chemical nature of our physical world. It can hold clues to many questions in the field of organic chemistry. For this reason, chemical analysis of organic compounds is essential to a range of applications across scientific disciplines.
Chemists, chemical engineers, dentists, doctors, and veterinarians all make use of elemental analysis. Scientists developing foods, household chemicals, pharmaceuticals, and plastics also rely on elemental analysis of organic compounds for research and quality control.
All organic compounds contain some level of carbon and hydrogen and many of them also contain nitrogen. Therefore, techniques that can reliably and accurately characterize and measure these three elements are vital to the elemental analysis of organic compounds. Here, we discuss the most common method of elemental analysis, CHNSO elemental analysis.
CHNSO Analysis to Define Elemental Compositions of Organic Compounds
CHNSO elemental analysis, which takes its name from the organic elements it investigates: Carbon (C), Hydrogen (H), Nitrogen (N), Sulfur (S) and Oxygen (O), is the most common form of elemental analysis. It is used to determine the amounts of these five elements within a sample.
CHNSO elemental analyzers use combustion analysis to assess the purity and chemical composition of a wide range of sample types, including solids, liquids, volatile, and viscous samples.
The methodology used by CHNSO analysis requires high-temperature combustion in an environment rich in oxygen. The technique, based on the Pregl-Dumas method, carries out combustion under both static and dynamic conditions to produce gases which are then passed through absorbent traps to reduce the sample to just carbon dioxide, water, nitrogen, and sulfur dioxide.
Several methods can be employed to detect the gases emitted via combustion. The most common are GC separation followed by thermal conductivity detection, partial separation by GC followed by thermal conductivity detection, and a series of separate infra-red and thermal conductivity cells for individual compound detection.
Analyzers manufactured for CHNSO elemental analysis can differ depending on the application they are being used for as instrumental requirements are reflected by the type of sample, its size, and the concentration of the analyte.
Data produced by CHNSO elemental analysis help scientists determine the chemical composition and structure of an organic compound. Alternative methods such as chemistry spectroscopic techniques, chromatographic procedures, and mass spectrometry determine a compound’s structure and are now favored for this type of analysis. Elemental analysis remains the most popular technique for determining chemical composition. This is due in part to its benefits of being fast, simple, and inexpensive.
CHNS elemental analyzers have been used across a range of analytical laboratories for more than 40 years, and their place as the most commonly used method of elemental analysis of organic compounds looks secure for the years to come. The method has few limitations, is accessible across the globe, and is already an established piece of equipment in many laboratories. Currently, there is no major work underway to enhance the technique, although scientists learn more about the process as more samples are tested.
References and Further Reading
Accreditation and Quality Assurance, 2006. Evaluation of analytical instrumentation. Part XIX CHNS elemental analysers. 11(11), pp.569-576. https://link.springer.com/article/10.1007/s00769-006-0185-x
Fadeeva, V., Tikhova, V. and Nikulicheva, O., 2008. Elemental analysis of organic compounds with the use of automated CHNS analyzers. Journal of Analytical Chemistry, 63(11), pp.1094-1106. https://link.springer.com/article/10.1134/S1061934808110142
Sieper, H., Kupka, H., Williams, T., Rossmann, A., Rummel, S., Tanz, N. and Schmidt, H., 2006. A measuring system for the fast simultaneous isotope ratio and elemental analysis of carbon, hydrogen, nitrogen and sulfur in food commodities and other biological material. Rapid Communications in Mass Spectrometry, 20(17), pp.2521-2527. https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/abs/10.1002/rcm.2619