Elemental analysis


Elemental analysis is a process where a sample of some material (e.g., soil, waste or drinking water, bodily fluids, minerals, chemical compounds) is analyzed for its elemental and sometimes isotopic composition.[citation needed] Elemental analysis can be qualitative (determining what elements are present), and it can be quantitative (determining how much of each are present). Elemental analysis falls within the ambit of analytical chemistry, the set of instruments involved in deciphering the chemical nature of our world.

Contents

History


Antoine Lavoisier is regarded as the inventor of elemental analysis as a quantitative, experimental tool to assess the chemical composition of a compound. At the time elemental analysis was based on gravimetric determination of specific absorbant materials before and after selective adsorption of the combustion gases.[1][2] Today fully automated systems based on thermal conductivity or infrared spectroscopy detection of the combustion gases, or other spectroscopic methods are used.

CHNX analysis


For organic chemists, elemental analysis or "EA" almost always refers to CHNX analysis—the determination of the mass fractions of carbon, hydrogen, nitrogen, and heteroatoms (X) (halogens, sulfur) of a sample.[citation needed] This information is important to help determine the structure of an unknown compound, as well as to help ascertain the structure and purity of a synthesized compound. In present day organic chemistry spectroscopic techniques (NMR, both 1H and 13C), mass spectrometry and chromatographic procedures have replaced EA as the primary technique for structural determination, although it still gives very useful complementary information. It is also the fastest and most inexpensive method to determine sample purity.

The most common form of elemental analysis, CHNS analysis, is accomplished by combustion analysis. Modern elemental analyzers are also capable of simultaneous determination of sulfur along with CHN in the same measurement run.[3][4][5][6]

Quantitative analysis


Quantitative analysis is the determination of the mass of each element or compound present.[7] Other quantitative methods include gravimetry, optical atomic spectroscopy, and neutron activation analysis.

Gravimetry is where the sample is dissolved and then the element of interest is precipitated and its mass measured or the element of interest is volatilized and the mass loss is measured.

Optical atomic spectroscopy includes flame atomic absorption, graphite furnace atomic absorption, and inductively coupled plasma atomic emission spectroscopy, which probe the outer electronic structure of atoms.

Neutron activation analysis involves the activation of a sample matrix through the process of neutron capture. The resulting radioactive target nuclei of the sample begin to decay, emitting gamma rays of specific energies that identify the radioisotopes present in the sample. The concentration of each analyte can be determined by comparison to an irradiated standard with known concentrations of each analyte.[8]

Qualitative analysis


To qualitatively determine which elements exist in a sample, the methods are mass spectrometric atomic spectroscopy, such as inductively coupled plasma mass spectrometry, which probes the mass of atoms; other spectroscopy which probes the inner electronic structure of atoms such as X-ray fluorescence, particle-induced X-ray emission, X-ray photoelectron spectroscopy, and Auger electron spectroscopy; and chemical methods such as the sodium fusion test and Schöniger oxidation.

Analysis of results


The analysis of results is performed by determining the ratio of elements from within the sample, and working out a chemical formula that fits with those results. This process is useful as it helps determine if a sample sent is a desired compound and confirms the purity of a compound. The accepted deviation of elemental analysis results from the calculated is 0.3%.[9]

See also


References


  1. ^ Pregl, Fritz (1917). Quantitative Micro-Analysis of Organic Substances. Berlin: Springer. ISBN 978-3-86444-914-7.
  2. ^ "Fritz Pregl - Nobel Lecture: Quantitative Micro-Analysis of Organic Substances" . www.nobelprize.org. Retrieved 2016-07-04.
  3. ^ "Aarhus University: Elemental Analysis Facility" . 3 July 2016. Archived from the original on 15 July 2015. Retrieved 3 July 2016.
  4. ^ sciences, Faculté des. "G.G. Hatch Stable Isotope Laboratory - Techniques - Quantitative Analysis" . www.isotope.uottawa.ca. Archived from the original on 2016-03-04. Retrieved 2016-07-04.
  5. ^ Sahu, Ramesh Chandra; Patel, Rajkishore; Ray, Bankim Chandra (2011-08-01). "Removal of hydrogen sulfide using red mud at ambient conditions". Fuel Processing Technology. 92 (8): 1587–1592. doi:10.1016/j.fuproc.2011.04.002 .
  6. ^ Käldström, Mats; Meine, Niklas; Farès, Christophe; Rinaldi, Roberto; Schüth, Ferdi (2012). "Fractionation of 'water-soluble lignocellulose' into C5/C6 sugars and sulfur-free lignins" (PDF). Green Chemistry. RSCPublishing. 16 (5): 2454–2462. doi:10.1039/C4GC00168K . S2CID 52969790 . Archived from the original (PDF) on 2019-02-25.
  7. ^ From Columbia Encyclopedia on answers.com: http://www.answers.com/library/Columbia+Encyclopedia-cid-2284496[permanent dead link]: chemical analysis
  8. ^ "Neutron Activation Analysis" . Analytical Chemistry Group. Retrieved 28 November 2012.
  9. ^ "CHN Elemental Microanalysis" . www.ucl.ac.ke. Retrieved 2017-11-03.







Categories: Elemental analysis | Analytical chemistry | Materials science




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