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Analytical chemistry is the study of the chemical composition of natural and artificial materials. Properties studied in analytical chemistry include geometric features such as molecular morphologies and distributions of species, as well as features such as composition and species identity. Unlike the sub disciplines inorganic chemistry and organic chemistry, analytical chemistry (like physical chemistry) is not restricted to any particular type of chemical compound or reaction.The contributions made by analytical chemists have played critical roles in the sciences ranging from the development of concepts and theories (pure science) to a variety of practical applications, such as biomedical applications, environmental monitoring, quality control of industrial manufacturing and forensic science (applied science).

Contents

Overview

Analytical chemistry is a sub-discipline of chemistry that has the broad mission of understanding the chemical composition of all matter and developing the tools and experiments to make either qualitative or quantitative measurements. In a nutshell, analytical chemistry applies measurement science principles along with an understanding of chemical systems to provide useful information; and it has significant overlap with other branches of chemistry through the measurement methods that it provides. For example, the field of bioanalysis is a growing area of analytical chemistry that addresses analytical questions in biochemistry, (the chemistry of life). Experimental physical chemistry and analytical chemistry show similarity in that both have a measurement science focus. While there is occasional overlap between these two disciplines, the goal of physical chemistry experiments is to determine the dynamics of how energy affects the chemical system by making kinetic, thermodynamic, and spectroscopic measurements, while analytical chemistry sometimes uses such energy-based measurements to determine matter-related properties such as chemical identity and quantity. Analytical chemistry is also focused on improvements in experimental design and the creation of new measurement tools to provide better chemical information.

Traditionally, analytical chemistry was particularly concerned with the questions of "what chemicals are present, what are their characteristics and in what quantities are they present?" These questions are often involved in questions that are more dynamic such as what chemical reaction an enzyme catalyzes or how fast it does it, or even more dynamic such as what is the transition state of the reaction. The next logical steps of understanding what it means, how it fits into a larger system, how can this result be generalized into theory, or how it can be used all result from information provided by analytical chemistry methods.

Analytical chemists work to improve the reliability of existing techniques to meet the demands for better chemical measurements which arise constantly in our society. They adapt proven methodologies to new kinds of materials or to answer new questions about their composition. They carry out research to discover completely new principles of measurement and are at the forefront of the utilization of major discoveries such as lasers and microchip devices for practical purposes. They make important contributions to many other fields as diverse as forensic chemistry, archaeology, and space science.

Modern analytical chemistry

Modern analytical chemistry is dominated by instrumental analysis. Many analytical chemists focus on a single type of instrument. Academics tend to either focus on new applications and discoveries or on new methods of analysis. The discovery of a chemical present in blood that increases the risk of cancer would be a discovery that an analytical chemist might be involved in. An effort to develop a new method might involve the use of a tunable laser to increase the specificity and sensitivity of a spectrometric method. Many methods, once developed, are kept purposely static so that data can be compared over long periods of time. This is particularly true in industrial quality assurance (QA), forensic and environmental applications. Analytical chemistry plays an increasingly important role in the pharmaceutical industry where, aside from QA, it is used in discovery of new drug candidates and in clinical applications where understanding the interactions between the drug and the patient are critical.

History

"Analytical" chemistry has been important since the early days of chemistry, providing methods for determining which elements and chemicals are present in the world around us. During this period significant analytical contributions to chemistry include the development of systematic elemental analysis by Justus von Liebig and systematized organic analysis based on the specific reactions of functional groups.

The first instrumental analysis was flame emissive spectrometry developed by Robert Bunsen and Gustav Kirchhoff who discovered rubidium (Rb) and caesium (Cs) in 1860.[1]

Most of the major developments in analytical chemistry take place after 1900. During this period instrumental analysis becomes progressively dominant in the field. In particular many of the basic spectroscopic and spectrometric techniques were discovered in the early 20th century and refined in the late 20th century.[2]

The separation sciences follow a similar time line of development and also become increasingly transformed into high performance instruments.[3] In the 1970s many of these techniques began to be used together to achieve a complete characterization of samples.

Starting in approximately the 1970s into the present day analytical chemistry has progressively become more inclusive of biological questions (bioanalytical chemistry), whereas it had previously been largely focused on inorganic or small organic molecules. Lasers have been increasingly used in chemistry as probes and even to start and influence a wide variety of reactions. The late 20th century also saw an expansion of the application of analytical chemistry from somewhat academic chemical questions to forensic, environmental, industrial and medical questions, such as in histology.[4]

Approaches

Most modern analytical chemistry can be categorized in terms of the analytical target (problem or field of application), and the analytical methods used. The journal Analytical Chemistry provides reviews of recent research in either analytical targets or analytical methods, alternating by year.

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By Analytical Targets

By Analytical Methods

Traditional analytical techniques

Although modern analytical chemistry is dominated by sophisticated instrumentation, the roots of analytical chemistry and some of the principles used in modern instruments are from traditional techniques many of which are still used today. These techniques also tend to form the backbone of most undergraduate analytical chemistry educational labs. Examples include:

Titration

Titration involves the addition of a reactant to a solution being analyzed until some equivalence point is reached. Often the amount of material in the solution being analyzed may be determined. Most familiar to those who have taken college chemistry is the acid-base titration involving a color changing indicator. There are many other types of titrations, for example potentiometric titrations. These titrations may use different types of indicators to reach some equivalence point.

Gravimetry

Gravimetric analysis involves determining the amount of material present by weighing the sample before and/or after some transformation. A common example used in undergraduate education is the determination of the amount of water in a hydrate by heating the sample to remove the water such that the difference in weight is due to the water lost.

Inorganic qualitative analysis

Inorganic qualitative analysis generally refers to a systematic scheme to confirm the presence of certain, usually aqueous, ions or elements by performing a series of reactions that eliminate ranges of possibilities and then confirms suspected ions with a confirming test. Sometimes small carbon containing ions are included in such schemes. With modern instrumentation these tests are rarely used but can be useful for educational purposes and in field work or other situations where access to state-of-the-art instruments are not available or expedient.

Instrumental Analysis

Block diagram of an analytical instrument showing the stimulus and measurement of response

Spectroscopy

Spectroscopy measures the interaction of the molecules with electromagnetic radiation. Spectroscopy consists of many different applications such as atomic absorption spectroscopy, atomic emission spectroscopy, ultraviolet-visible spectroscopy, x-ray fluorescence spectroscopy, infrared spectroscopy, Raman spectroscopy, nuclear magnetic resonance spectroscopy, photoemission spectroscopy, Mössbauer spectroscopy and so on.

Mass Spectrometry

Mass spectrometry measures mass-to-charge ratio of molecules using electric and magnetic fields. There are several ionization methods: electron impact, chemical ionization, electrospray, fast atom bombardment, matrix assisted laser desorption ionization, and others. Also, mass spectrometry is categorized by approaches of mass analyzers: magnetic-sector,quadrupole mass analyzer, quadrupole ion trap, Time-of-flight, Fourier transform ion cyclotron resonance, and so on.

Crystallography

Crystallography is a technique that characterizes the chemical structure of materials at the atomic level by analyzing the diffraction patterns of usually x-rays that have been deflected by atoms in the material. From the raw data the relative placement of atoms in space may be determined.

Electrochemical Analysis

Electroanalytical methods measure the potential (volts) and/or current (amps) in an electrochemical cell containing the analyte.[5][6] These methods can be categorized according to which aspects of the cell are controlled and which are measured. The three main categories are potentiometry (the difference in electrode potentials is measured), coulometry (the cell's current is measured over time), and voltammetry (the cell's current is measured while actively altering the cell's potential).

Thermal Analysis

Calorimetry and thermogravimetric analysis measure the interaction of a material and heat.

Separation

Separation processes are used to decrease the complexity of material mixtures. Chromatography and electrophoresis are representative of this field.

Hybrid Techniques

Combinations of the above techniques produce "hybrid" or "hyphenated" techniques.[7][8][9][10][11] Several examples are in popular use today and new hybrid techniques are under development. For example, Gas chromatography-mass spectrometry, LC-MS, GC-IR, LC-NMR, LC-IR, CE-MS, and so on.

Hyphenated separation techniques refers to a combination of two (or more) techniques to detect and separate chemicals from solutions. Most often the other technique is some form of chromatography. Hyphenated techniques are widely used in chemistry and biochemistry. A slash is sometimes used instead of hyphen, especially if the name of one of the methods contains a hyphen itself.

Examples of hyphenated techniques:

  1. LC-MS (or HPLC-MS)
  2. HPLC/ESI-MS
  3. LC-DAD
  4. CE-MS
  5. CE-UV
  6. GC-MS
  7. LC-IR

Microscopy

The visualization of single molecules, single cells, biological tissues and nano- micro materials is very important and attractive approach in analytical science. Also, hybridization with other traditional analytical tools is revolutionizing analytical science. Microscopy can be categorized into three different fields: optical microscopy, electron microscopy, and scanning probe microscopy. Recently, this field is rapidly progressing because of the rapid development of computer and camera industries.

Lab-on-a-chip

Devices that integrate (multiple) laboratory functions on a single chip of only millimeters to a few square centimeters in size and that are capable of handling extremely small fluid volumes down to less than pico liters.

Methods and data analysis

Standard Curve

A standard method for analysis of concentration involves the creation of a calibration curve. This allows for determination of the amount of a chemical in a material by comparing the results of unknown sample to those of a series known standards. If the concentration of element or compound in a sample is too high for the detection range of the technique, it can simply be diluted in a pure solvent. If the amount in the sample is below an instrument's range of measurement, the method of addition can be used. In this method a known quantity of the element or compound under study is added, and the difference between the concentration added, and the concentration observed is the amount actually in the sample.

Internal Standards

Sometimes an internal standard is added at a known concentration directly to an analytical sample to aid in quantitation. The amount of analyte present is then determined relative to the internal standard as a calibrant.

Trends

Analytical chemistry research is largely driven by performance (sensitivity, selectivity, robustness, linear range, accuracy, precision, and speed), and cost (purchase, operation, training, time, and space). Among the main branches of contemporary analytical atomic spectrometry, the most widespread and universal are optical and mass spectrometry (see Prospects in Analytical Atomic Spectrometry). In the direct elemental analysis of solid samples, the new leaders are laser-induced breakdown and laser ablation mass spectrometry, and the related techniques with transfer of the laser ablation products into inductively coupled plasma. Advances in design of diode lasers and optical parametric oscillators promote developments in fluorescence and ionization spectrometry and also in absorption techniques where uses of optical cavities for increased effective absorption pathlength are expected to expand. Steady progress and growth in applications of plasma- and laser-based methods are noticeable. An interest towards the absolute (standardless) analysis has revived, particularly in the emission spectrometry.

A lot of effort is put in shrinking the analysis techniques to chip size. Although there are few examples of such systems competitive with traditional analysis techniques, potential advantages include size/portability, speed, and cost. (micro Total Analysis System (µTAS) or Lab-on-a-chip). Microscale chemistry reduces the amounts of chemicals used.

Much effort is also put into analyzing biological systems. Examples of rapidly expanding fields in this area are:

  • Genomics - DNA sequencing and its related research. Genetic fingerprinting and DNA microarray are very popular tools and research fields.
  • Proteomics - the analysis of protein concentrations and modifications, especially in response to various stressors, at various developmental stages, or in various parts of the body.
  • Metabolomics - similar to proteomics, but dealing with metabolites.
  • Transcriptomics- mRNA and its associated field
  • Lipidomics - lipids and its associated field
  • Peptidomics - peptides and its associated field
  • Metalomics - similar to proteomics and metabolomics, but dealing with metal concentrations and especially with their binding to proteins and other molecules.

Analytical chemistry has played critical roles in the understanding of basic science to a variety of practical applications, such as biomedical applications, environmental monitoring, quality control of industrial manufacturing, forensic science and so on.

The recent developments of computer automation and information technologies have innervated analytical chemistry to initiate a number of new biological fields. For example, automated DNA sequencing machines were the basis to complete human genome projects leading to the birth of genomics. Protein identification and peptide sequencing by mass spectrometry opened a new field of proteomics. Furthermore, a number of ~omics based on analytical chemistry have become important areas in modern biology.

Also, analytical chemistry has been an indispensable area in the development of nanotechnology. Surface characterization instruments, electron microscopes and scanning probe microscopes enables scientists to visualize atomic structures with chemical characterizations.

Analytical chemistry is pursuing the development of practical applications and commercial instruments rather than elucidating scientific fundamentals. This may be an arguable difference from overlapping science areas such as physical chemistry and biophysics, although there isn't any distinct boundaries among disciplines in contemporary science and technology. However, this aspect may attract many engineers' interest; thus, it is not difficult to see papers from engineering departments in analytical chemistry journals.

Among active contemporary analytical chemistry research fields, micro total analysis system is considered as a great promise of revolutionary technology. In this approach, integrated and miniaturized analytical systems are being developed to control and analyze single cells and single molecules. This cutting-edge technology has a promising potential of leading a new revolution in science as integrated circuits did in computer developments.

Academic resources

See also

Notes and references

  1. ^ ANALYTICAL SCIENCES 2001, VOL.17 SUPPLEMENT [1], Basic Education in Analytical Chemistry
  2. ^ Talanta Volume 51, Issue 5, p921-933 [2], Review of analytical next term measurements facilitated by drop formation technology
  3. ^ TrAC Trends in Analytical Chemistry Volume 21, Issues 9-10, Pages 547-557 [3], History of gas chromatography
  4. ^ Talanta, Volume 36, Issues 1-2, January-February 1989, Pages 1-9 [4] History of analytical chemistry in the U.S.A.
  5. ^ Bard, A.J.; Faulkner, L.R. Electrochemical Methods: Fundamentals and Applications. New York: John Wiley & Sons, 2nd Edition, 2000.
  6. ^ Skoog, D.A.; West, D.M.; Holler, F.J. Fundamentals of Analytical Chemistry New York: Saunders College Publishing, 5th Edition, 1988.
  7. ^ Wilkins CL (1983). "Hyphenated techniques for analysis of complex organic mixtures". Science 222 (4621): 291–6. doi:10.1126/science.6353577. PMID 6353577.  
  8. ^ Holt RM, Newman MJ, Pullen FS, Richards DS, Swanson AG (1997). "High-performance liquid chromatography/NMR spectrometry/mass spectrometry: further advances in hyphenated technology". Journal of mass spectrometry : JMS 32 (1): 64–70. doi:10.1002/(SICI)1096-9888(199701)32:1<64::AID-JMS450>3.0.CO;2-7. PMID 9008869.  
  9. ^ Ellis LA, Roberts DJ (1997). "Chromatographic and hyphenated methods for elemental speciation analysis in environmental media". Journal of chromatography. A 774 (1-2): 3–19. doi:10.1016/S0021-9673(97)00325-7. PMID 9253184.  
  10. ^ Guetens G, De Boeck G, Wood M, Maes RA, Eggermont AA, Highley MS, van Oosterom AT, de Bruijn EA, Tjaden UR (2002). "Hyphenated techniques in anticancer drug monitoring. I. Capillary gas chromatography-mass spectrometry". Journal of chromatography. A 976 (1-2): 229–38. doi:10.1016/S0021-9673(02)01228-1. PMID 12462614.  
  11. ^ Guetens G, De Boeck G, Highley MS, Wood M, Maes RA, Eggermont AA, Hanauske A, de Bruijn EA, Tjaden UR (2002). "Hyphenated techniques in anticancer drug monitoring. II. Liquid chromatography-mass spectrometry and capillary electrophoresis-mass spectrometry". Journal of chromatography. A 976 (1-2): 239–47. doi:10.1016/S0021-9673(02)01227-X. PMID 12462615.  
  12. ^ Elsevier. "Analytica Chimica Acta". http://www.sciencedirect.com/science/journal/00032670. Retrieved 13 July 2009.  

External links


Study guide

Up to date as of January 14, 2010
(Redirected to Topic:Analytical chemistry article)

From Wikiversity

Contents

Welcome to the Department of Analytical Chemistry, part of the School of Chemistry.

Chemistry is the study of matter at the atomic and molecular scale.

The Department of Analytical Chemistry is interested in developing course materials and sustainable communities for Analytical Chemistry.

Textbook resources can be found on Wikibooks. Here, the focus is on developing course notes to supplement textbooks.

Participants in online learning should look at the modules listed below and see which ones they are interested in.

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Feel free to join in! Things will be evolving as we go along. Feel free to make changes as you see fit!

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Remember, Wikiversity has adopted the "learning by doing" model for education. Lessons should center on learning activities for Wikiversity participants. We learn by doing.

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Preliminaries

These topics constitute the essentials of chemistry. Knowledge of these topics should be mastered.

Chemical element

Course notes

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Simple English

Analytical chemistry is a branch of chemistry. It tries to analyze chemicals in different things. A sample job would be trying to see how much zinc is in a piece of brass. There are several tools, like chromatography, that analytical chemists use. Flame tests can be used for a basic analysis.


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