Analytical chemistry

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Analytical chemistry is the analysis of material samples to gain an understanding of their chemical composition, structure and function.

Contents 1 Introduction 2 History 3 Types 4 Techniques 5 Methods 6 Trends 7 Specific Technologies and Instrumentation 8 See also 9 References

[edit] Introduction

Analytical chemistry is a sub discipline of chemistry that has the broad mission of understanding the chemical nature of all matter. This differs from other sub disciplines of chemistry in that it is not intended to understand the physical basis for the observed chemistry as with physical chemistry and it is not intended to control or direct chemistry as is often the case in organic chemistry. Analytical chemistry generally does not attempt to use chemistry or understand its basis; however, these are common outgrowths of analytical chemistry research. Analytical chemistry has significant overlap with other branches of chemistry, especially those that are focused on a certain broad class of chemicals, such as organic chemistry, inorganic chemistry or biochemistry, as opposed to a particular way of understanding chemistry, such as theoretical chemistry. For example the field of bioanalytical chemistry is a growing area of analytical chemistry that addresses all analytical questions in biochemistry, (the chemistry of life). Analytical chemistry and experimental physical chemistry, however, have a unique relationship in that they are very unrelated in their mission but often share the most in common in the tools used in experiments.

Analytical chemistry is 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. Although analytical chemistry addresses these types of questions it stops after they are answered. The logical next 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 are not analytical chemistry. Since analytical chemistry is based on firm experimental evidence and limits itself to some fairly simple questions to the general public it is most closely associated with hard numbers such as how much lead is in drinking water.

Modern analytical chemistry is dominated by instrumental analysis. There are so many different types of instruments today that it can seem like a confusing array of acronyms rather than a unified field of study. 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.

[edit] History

Much of early chemistry (1661-~1900AD) was analytical chemistry since the questions of what elements and chemicals were present in the world around us and what are their fundamental natures is very much in the realm of analytical chemistry. There was also significant early progress in synthesis and theory which of course are not analytical chemistry. 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 Rb and 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. 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.^[4]

[edit] Types

Traditionally, analytical chemistry has been split into two main types, qualitative and quantitative:

• Qualitative

Qualitative inorganic analysis seeks to establish the presence of a given element or inorganic compound in a sample.

Qualitative organic analysis seeks to establish the presence of a given functional group or organic compound in a sample.

• Quantitative

Quantitative analysis seeks to establish the amount of a given element or compound in a sample.

Most modern analytical chemistry is categorized by two different approaches such as analytical targets or analytical methods. Analytical Chemistry (journal) reviews two different approaches alternatively in the issue 12 of each year.

• By Analytical Targets
  • Bioanalytical chemistry
  • Material analysis
  • Chemical analysis
  • Environmental analysis
  • Forensics

• By Analytical Methods
  • Spectroscopy
  • Mass Spectrometry
  • Chromatography & Electrophoresis
  • Crystallography
  • Microscopy
  • Electrochemistry

[edit] Techniques

There are many techniques available for the analysis of materials; however, they are all based on the material's interaction with energy. This interaction permits the creation of a signal that is subsequently detected and processed for its information content.

The types of analysis techniques conform with the various types of energy:

• Spectroscopic Analysis

Spectroscopy measures the interaction of the material with electromagnetic radiation.

• Electrochemical Analysis

Electrochemistry measures the interaction of the material with an electric field.

• Mass Analysis

Gravimetric analysis measures the interaction of the material and a gravitational field.

Mass spectrometry measures the interaction of charged materials and electric and magnetic fields.

• Thermal Analysis

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

The detection and analysis of multiple simultaneous signals is the subject of cutting-edge research in analytical chemistry. In order to utilize the techniques available currently, complex material mixtures must be separated into simpler samples for individual analysis.

• Separation Science

Separation processes are used to decrease the complexity of material mixtures. The most utilized separation method is chromatography.

After the material is sufficiently isolated and a signal is generated, the signal must be detected and interpreted.

• Data Acquisition and Analysis

Specific data acquisition and data analysis techniques are required to obtain the information produced by the various techniques for material analysis named above. Research and development in this area of analytical chemistry involves interdisciplinary efforts in physics, electronics, optics, statistics and computer science.

• Hybrid Techniques

Combinations of the above techniques produce "hybrid" or "hyphenated" techniques. Several examples are in popular use today and new hybrid techniques are under development.

[edit] Methods

Analytical methods rely on scrupulous attention to cleanliness, sample preparation, accuracy and precision.

Many practitioners will keep all their glassware in acid to prevent contamination, samples will be re-run many times over, and equipment will be washed in specially pure solvents.

A standard method for analysis of concentration involves the creation of a calibration curve.

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.

[edit] 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).

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 stresssors, 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.

[edit] Specific Technologies and Instrumentation

• Atomic absorption spectroscopy (AAS)
• Atomic fluorescence spectroscopy (AFS)
• Alpha particle X-ray spectrometer (APXS)
• Capillary electrophoresis (CE)
• Chromatography
• Cyclic Voltammetry (CV)
• Differential scanning calorimetry (DSC)
• Electron paramagnetic resonance (EPR)
• Electron spin resonance (ESR)
• Field flow fractionation (FFF)
• Ion Microprobe (IM)
• Instrumental mass fractionation (IMF)
• Ion selective electrode (ISE) eg. determination of pH
• Laser Induced Breakdown Spectroscopy (LIBS)
• Mass spectrometry (MS)
• Mossbauer spectroscopy
• Nuclear magnetic resonance (NMR)
• Particle induced X-ray emission spectroscopy (PIXE)
• Raman spectroscopy
• Refractive index
• Resonance enhanced multi-photon ionization (REMPI)
• Scanning transmission X-ray microscopy (STXM)
• X-ray fluorescence spectroscopy (XRF)
• X-ray microscopy (XRM)

[edit] See also

• Important publications in analytical chemistry
• American Chemical Society: Division of Analytical Chemistry

[edit] 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 analyticalnext 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.