Analytical chemistry studies and uses instruments and methods used 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.
Analytical chemistry consists of classical, wet chemical methods and
modern, instrumental methods. Classical qualitative methods use
separations such as precipitation, extraction, and distillation.
Identification may be based on differences in color, odor, melting
point, boiling point, radioactivity or reactivity. Classical
quantitative analysis uses mass or volume changes to quantify amount.
Instrumental methods may be used to separate samples using
chromatography, electrophoresis or field flow fractionation. Then
qualitative and quantitative analysis can be performed, often with the
same instrument and may use light interaction, heat interaction,
electric fields or magnetic fields . Often the same instrument can
separate, identify and quantify an analyte.
Analytical chemistry is also focused on improvements in experimental
design, chemometrics, and the creation of new measurement tools.
Analytical chemistry has broad applications to forensics, medicine,
science and engineering.
2 Classical methods
2.1 Qualitative analysis
2.1.1 Chemical tests
2.1.2 Flame test
2.2 Quantitative analysis
2.2.1 Gravimetric analysis
2.2.2 Volumetric analysis
3 Instrumental methods
3.2 Mass spectrometry
3.3 Electrochemical analysis
3.4 Thermal analysis
3.6 Hybrid techniques
5.1 Standard curve
5.2 Internal standards
5.3 Standard addition
6 Signals and noise
6.1 Thermal noise
6.2 Shot noise
6.3 Flicker noise
6.4 Environmental noise
6.5 Noise reduction
8 See also
10 Further reading
11 External links
Gustav Kirchhoff (left) and
Robert Bunsen (right)
Analytical chemistry has been important since the early days of
chemistry, providing methods for determining which elements and
chemicals are present in the object in question. During this period
significant contributions to analytical chemistry include the
development of systematic elemental analysis by
Justus von Liebig
Justus von Liebig and
systematized organic analysis based on the specific reactions of
The first instrumental analysis was flame emissive spectrometry
Robert Bunsen and
Gustav Kirchhoff who discovered
rubidium (Rb) and caesium (Cs) in 1860.
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.
The separation sciences follow a similar time line of development and
also become increasingly transformed into high performance
instruments. In the 1970s many of these techniques began to be used
together as hybrid techniques to achieve a complete characterization
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 initiate 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.
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
The presence of copper in this qualitative analysis is indicated by
the bluish-green color of the flame
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
A qualitative analysis determines the presence or absence of a
particular compound, but not the mass or concentration. By definition,
qualitative analyses do not measure quantity.
Further information: Chemical test
There are numerous qualitative chemical tests, for example, the acid
test for gold and the
Kastle-Meyer test for the presence of blood.
Further information: Flame test
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
Further information: Quantitative analysis (chemistry)
Quantitative analysis is the measurement of the quantities of
particular chemical constituents present in a substance.
Further information: Gravimetric analysis
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 loss of water.
Further information: 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 chemistry during secondary education
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.
Main article: Instrumental analysis
Block diagram of an analytical instrument showing the stimulus and
measurement of response
This section needs expansion. You can help by adding to it. (April
Further information: Spectroscopy
Spectroscopy measures the interaction of the molecules with
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, dual
polarization interferometry, nuclear magnetic resonance spectroscopy,
Mössbauer spectroscopy and so on.
Further information: Mass spectrometry
An accelerator mass spectrometer used for radiocarbon dating and other
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
Further information: Electroanalytical method
Electroanalytical methods measure the potential (volts) and/or current
(amps) in an electrochemical cell containing the analyte. These
methods can be categorized according to which aspects of the cell are
controlled and which are measured. The four main categories are
potentiometry (the difference in electrode potentials is measured),
coulometry (the transferred charge is measured over time), amperometry
(the cell's current is measured over time), and voltammetry (the
cell's current is measured while actively altering the cell's
Calorimetry and Thermal analysis
Calorimetry and thermogravimetric analysis measure the interaction of
a material and heat.
Separation of black ink on a thin layer chromatography plate
Further information: Separation process, Chromatography, and
Separation processes are used to decrease the complexity of material
mixtures. Chromatography, electrophoresis and Field Flow Fractionation
are representative of this field.
Combinations of the above techniques produce a "hybrid" or
"hyphenated" technique. Several examples are in
popular use today and new hybrid techniques are under development. For
example, gas chromatography-mass spectrometry, gas
chromatography-infrared spectroscopy, liquid chromatography-mass
spectrometry, liquid chromatography-NMR spectroscopy. liquid
chromagraphy-infrared spectroscopy and capillary electrophoresis-mass
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.
Fluorescence microscope image of two mouse cell nuclei in prophase
(scale bar is 5 µm)
Further information: Microscopy
The visualization of single molecules, single cells, biological
tissues and nanomaterials is an important and attractive approach in
analytical science. Also, hybridization with other traditional
analytical tools is revolutionizing analytical science.
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 the
computer and camera industries.
Microfluidics and 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
Main article: Approximation error
Error can be defined as numerical difference between observed value
and true value.
In error the true value and observed value in chemical analysis can be
related with each other by the equation
E = absolute error,
O = observed value,
T = true value.
Error of a measurement is an inverse measure of accurate measurement
i.e. smaller the error greater the accuracy of the measurement. Errors
are expressed relatively as:
displaystyle frac E T
× 100 = % error,
displaystyle frac E T
× 1000 = per thousand error
See also: Analytical quality control
A calibration curve plot showing limit of detection (LOD), limit of
quantification (LOQ), dynamic range, and limit of linearity (LOL)
A general 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 of 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.
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. An ideal internal standard is isotopically-enriched
analyte which gives rise to the method of isotope dilution.
The method of standard addition is used in instrumental analysis to
determine concentration of a substance (analyte) in an unknown sample
by comparison to a set of samples of known concentration, similar to
using a calibration curve.
Standard addition can be applied to most
analytical techniques and is used instead of a calibration curve to
solve the matrix effect problem.
Signals and noise
One of the most important components of analytical chemistry is
maximizing the desired signal while minimizing the associated
noise. The analytical figure of merit is known as the
signal-to-noise ratio (S/N or SNR).
Noise can arise from environmental factors as well as from fundamental
Main article: Johnson–Nyquist noise
Thermal noise results from the motion of charge carriers (usually
electrons) in an electrical circuit generated by their thermal motion.
Thermal noise is white noise meaning that the power spectral density
is constant throughout the frequency spectrum.
The root mean square value of the thermal noise in a resistor is given
displaystyle v_ RMS = sqrt 4k_ B TRDelta f ,
where kB is Boltzmann's constant, T is the temperature, R is the
displaystyle Delta f
is the bandwidth of the frequency
Main article: Shot noise
Shot noise is a type of electronic noise that occurs when the finite
number of particles (such as electrons in an electronic circuit or
photons in an optical device) is small enough to give rise to
statistical fluctuations in a signal.
Shot noise is a
Poisson process and the charge carriers that make up
the current follow a Poisson distribution. The root mean square
current fluctuation is given by
displaystyle i_ RMS = sqrt 2,e,I,Delta f
where e is the elementary charge and I is the average current. Shot
noise is white noise.
Main article: flicker noise
Flicker noise is electronic noise with a 1/ƒ frequency spectrum; as f
increases, the noise decreases.
Flicker noise arises from a variety of
sources, such as impurities in a conductive channel, generation and
recombination noise in a transistor due to base current, and so on.
This noise can be avoided by modulation of the signal at a higher
frequency, for example through the use of a lock-in amplifier.
Noise in a thermogravimetric analysis; lower noise in the middle of
the plot results from less human activity (and environmental noise) at
Environmental noise arises from the surroundings of the analytical
instrument. Sources of electromagnetic noise are power lines, radio
and television stations, wireless devices, Compact fluorescent
lamps and electric motors. Many of these noise sources are narrow
bandwidth and therefore can be avoided.
Temperature and vibration
isolation may be required for some instruments.
Noise reduction can be accomplished either in computer hardware or
software. Examples of hardware noise reduction are the use of shielded
cable, analog filtering, and signal modulation. Examples of software
noise reduction are digital filtering, ensemble average, boxcar
average, and correlation methods.
Analytical chemistry has applications including in forensic science,
bioanalysis, clinical analysis, environmental analysis, and materials
Analytical chemistry research is largely driven by
performance (sensitivity, detection limit, selectivity, robustness,
dynamic range, 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. 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. The use of plasma- and laser-based methods is
increasing. An interest towards absolute (standardless) analysis has
revived, particularly in emission spectrometry.
Great effort is being 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
Many developments improve the analysis of biological systems. Examples
of rapidly expanding fields in this area are genomics, DNA sequencing
and related research in genetic fingerprinting and DNA microarray;
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, which deals
with metabolites; transcriptomics, including mRNA and associated
fields; lipidomics - lipids and its associated fields; peptidomics -
peptides and its associated fields; and metalomics, dealing with metal
concentrations and especially with their binding to proteins and other
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 extended analytical chemistry into 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.
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 portal
List of chemical analysis methods
List of materials analysis methods
Important publications in analytical chemistry
Sensory analysis - in the field of Food science
Quality of analytical results
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