Elemental analysis

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Modern simultaneous CHNS combustion analyzer Elementar modern elemental analyzer 2011.jpg
Modern simultaneous CHNS combustion analyzer

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 is present). Elemental analysis falls within the ambit of analytical chemistry, the instruments involved in deciphering the chemical nature of our world.

Contents

History

The Kaliapparat for elementary analysis in the Liebig Museum in Giessen, Germany. Liebigmuseum Elementaranalyse.jpg
The Kaliapparat for elementary analysis in the Liebig Museum in Giessen, Germany.

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 the gravimetric determination of specific absorbent 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. However, it still gives very useful complementary information.

Elemental Analyzer System Elemental Analyzer System.jpg
Elemental Analyzer System

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 determines 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, 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 the 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

Related Research Articles

<span class="mw-page-title-main">Analytical chemistry</span> Study of the separation, identification, and quantification of matter

Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separation isolates analytes. Qualitative analysis identifies analytes, while quantitative analysis determines the numerical amount or concentration.

<span class="mw-page-title-main">Atomic absorption spectroscopy</span> Type of spectroanalytical ciao

Atomic absorption spectroscopy (AAS) and atomic emission spectroscopy (AES) is a spectroanalytical procedure for the quantitative determination of chemical elements by free atoms in the gaseous state. Atomic absorption spectroscopy is based on absorption of light by free metallic ions.

<span class="mw-page-title-main">Chalcogen</span> Group of chemical elements

The chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive elements polonium (Po) and livermorium (Lv). Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. The word "chalcogen" is derived from a combination of the Greek word khalkόs (χαλκός) principally meaning copper, and the Latinized Greek word genēs, meaning born or produced.

Chemistry is the physical science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions.

<span class="mw-page-title-main">Electron ionization</span> Ionization technique

Electron ionization is an ionization method in which energetic electrons interact with solid or gas phase atoms or molecules to produce ions. EI was one of the first ionization techniques developed for mass spectrometry. However, this method is still a popular ionization technique. This technique is considered a hard ionization method, since it uses highly energetic electrons to produce ions. This leads to extensive fragmentation, which can be helpful for structure determination of unknown compounds. EI is the most useful for organic compounds which have a molecular weight below 600. Also, several other thermally stable and volatile compounds in solid, liquid and gas states can be detected with the use of this technique when coupled with various separation methods.

A radioactive tracer, radiotracer, or radioactive label is a synthetic derivative of a natural compound in which one or more atoms have been replaced by a radionuclide. By virtue of its radioactive decay, it can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products. Radiolabeling or radiotracing is thus the radioactive form of isotopic labeling. In biological contexts, experiments that use radioisotope tracers are sometimes called radioisotope feeding experiments.

<span class="mw-page-title-main">Chemical structure</span> Organized way in which molecules are ordered and sorted

A chemical structure of a molecule is a spatial arrangement of its atoms and their chemical bonds. Its determination includes a chemist's specifying the molecular geometry and, when feasible and necessary, the electronic structure of the target molecule or other solid. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together and can be represented using structural formulae and by molecular models; complete electronic structure descriptions include specifying the occupation of a molecule's molecular orbitals. Structure determination can be applied to a range of targets from very simple molecules to very complex ones.

<span class="mw-page-title-main">Gravimetric analysis</span> Quantitative determination of a chemical species based on its mass

Gravimetric analysis describes a set of methods used in analytical chemistry for the quantitative determination of an analyte based on its mass. The principle of this type of analysis is that once an ion's mass has been determined as a unique compound, that known measurement can then be used to determine the same analyte's mass in a mixture, as long as the relative quantities of the other constituents are known.

<span class="mw-page-title-main">Nuclear magnetic resonance spectroscopy</span> Laboratory technique

Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique based on re-orientation of atomic nuclei with non-zero nuclear spins in an external magnetic field. This re-orientation occurs with absorption of electromagnetic radiation in the radio frequency region from roughly 4 to 900 MHz, which depends on the isotopic nature of the nucleus and increased proportionally to the strength of the external magnetic field. Notably, the resonance frequency of each NMR-active nucleus depends on its chemical environment. As a result, NMR spectra provide information about individual functional groups present in the sample, as well as about connections between nearby nuclei in the same molecule. As the NMR spectra are unique or highly characteristic to individual compounds and functional groups, NMR spectroscopy is one of the most important methods to identify molecular structures, particularly of organic compounds.

In analytical chemistry, ashing or ash content determination is the process of mineralization by complete combustion for preconcentration of trace substances prior to a chemical analysis, such as chromatography, or optical analysis, such as spectroscopy.

Combustion analysis is a method used in both organic chemistry and analytical chemistry to determine the elemental composition of a pure organic compound by combusting the sample under conditions where the resulting combustion products can be quantitatively analyzed. Once the number of moles of each combustion product has been determined the empirical formula or a partial empirical formula of the original compound can be calculated.

In a chemical analysis, the internal standard method involves adding the same amount of a chemical substance to each sample and calibration solution. The internal standard responds proportionally to changes in the analyte and provides a similar, but not identical, measurement signal. It must also be absent from the sample matrix to ensure there is no other source of the internal standard present. Taking the ratio of analyte signal to internal standard signal and plotting it against the analyte concentrations in the calibration solutions will result in a calibration curve. The calibration curve can then be used to calculate the analyte concentration in an unknown sample.

In analytical chemistry, quantitative analysis is the determination of the absolute or relative abundance of one, several or all particular substance(s) present in a sample.

Physical organic chemistry, a term coined by Louis Hammett in 1940, refers to a discipline of organic chemistry that focuses on the relationship between chemical structures and reactivity, in particular, applying experimental tools of physical chemistry to the study of organic molecules. Specific focal points of study include the rates of organic reactions, the relative chemical stabilities of the starting materials, reactive intermediates, transition states, and products of chemical reactions, and non-covalent aspects of solvation and molecular interactions that influence chemical reactivity. Such studies provide theoretical and practical frameworks to understand how changes in structure in solution or solid-state contexts impact reaction mechanism and rate for each organic reaction of interest.

<span class="mw-page-title-main">Mass (mass spectrometry)</span> Physical quantities being measured

The mass recorded by a mass spectrometer can refer to different physical quantities depending on the characteristics of the instrument and the manner in which the mass spectrum is displayed.

This glossary of chemistry terms is a list of terms and definitions relevant to chemistry, including chemical laws, diagrams and formulae, laboratory tools, glassware, and equipment. Chemistry is a physical science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions; it features an extensive vocabulary and a significant amount of jargon.

<span class="mw-page-title-main">Atomic emission spectroscopy</span> Analytical method using radiation to identify chemical elements in a sample

Atomic emission spectroscopy (AES) is a method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular wavelength to determine the quantity of an element in a sample. The wavelength of the atomic spectral line in the emission spectrum gives the identity of the element while the intensity of the emitted light is proportional to the number of atoms of the element. The sample may be excited by various methods.

<span class="mw-page-title-main">Isotope</span> Different atoms of the same element

Isotopes are distinct nuclear species of the same chemical element. They have the same atomic number and position in the periodic table, but differ in nucleon numbers due to different numbers of neutrons in their nuclei. While all isotopes of a given element have similar chemical properties, they have different atomic masses and physical properties.

Nuclear forensics is the investigation of nuclear materials to find evidence for the source, the trafficking, and the enrichment of the material. The material can be recovered from various sources including dust from the vicinity of a nuclear facility, or from the radioactive debris following a nuclear explosion.

Structural chemistry is a part of chemistry and deals with spatial structures of molecules and solids. For structure elucidation a range of different methods is used. One has to distinguish between methods that elucidate solely the connectivity between atoms (constitution) and such that provide precise three dimensional information such as atom coordinates, bond lengths and angles and torsional angles.

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. Bibcode:2011FuPrT..92.1587S. 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. 16 (5). RSCPublishing: 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%5B%5D: chemical analysis
  8. "Neutron Activation Analysis". Analytical Chemistry Group. Archived from the original on 2 January 2018. Retrieved 28 November 2012.
  9. "CHN Elemental Microanalysis". www.ucl.ac.ke. Archived from the original on 2017-10-09. Retrieved 2017-11-03.