Analytical chemistry

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

Types

Analytical chemistry can be 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 quantitative. Quantitative analysis can be further split into different areas of study. The material can be analyzed for the amount of an element, or for the amount of an element in a specific chemical species. The latter is of particular interest in biological systems; the molecules of life contain carbon, hydrogen, oxygen, nitrogen, and others, in many complex structures.

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.

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.

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. (Total Analysis System or lab on a chip)

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

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.
Metalomics - similar to proteomics and metabolomics, but dealing with metal concentrations and especially with their binding to proteins and other molecules.

Important publications in analytical chemistry
High performance liquid chromatography (HPLC)
Gas-liquid chromatography (GC)
Nuclear magnetic resonance (NMR)
Mass spectrometry (MS)
Laser Induced Breakdown spectroscopy (LIBS)
Scanning Transmission X-ray Microscopy (STXM)
Resonance Enhanced Multi-Photon Ionization (REMPI)
Instrumental mass fractionation (IMF)
Ion Microprobe (IM)
Mossbauer spectroscopy
Raman spectroscopy
X-Ray fluorescence spectroscopy (XRF)
Alpha Particle X-Ray spectrometer (APXS)
TES and miniTES
Particle Induced X-ray Emission spectroscopy (PIXE)
MGS
EPE
THEMIS

Analytical chemistry

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Types

Techniques

Methods

Trends

See also