cuvette
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A cuvette ( French: cuvette = "little vessel") is a small tube-like container with straight sides and a circular or square cross section. It is sealed at one end, and made of a clear, transparent material such as
plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
,
glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...
, or
fused quartz Fused quartz, fused silica or quartz glass is a glass consisting of almost pure silica (silicon dioxide, SiO2) in amorphous (non-crystalline) form. This differs from all other commercial glasses in which other ingredients are added which change ...
. Cuvettes are designed to hold samples for
spectroscopic Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...
measurement, where a beam of light is passed through the sample within the cuvette to measure the
absorbance Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative lo ...
,
transmittance Transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is th ...
,
fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
intensity, fluorescence polarization, or fluorescence lifetime of the sample. This measurement is done with a spectrophotometer.


Overview

Traditional
ultraviolet–visible spectroscopy UV spectroscopy or UV–visible spectrophotometry (UV–Vis or UV/Vis) refers to absorption spectroscopy or reflectance spectroscopy in part of the ultraviolet and the full, adjacent visible regions of the electromagnetic spectrum. Being relative ...
or
fluorescence spectroscopy Fluorescence spectroscopy (also known as fluorimetry or spectrofluorometry) is a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electron ...
uses samples that are liquid. Often the sample is a
solution Solution may refer to: * Solution (chemistry), a mixture where one substance is dissolved in another * Solution (equation), in mathematics ** Numerical solution, in numerical analysis, approximate solutions within specified error bounds * Soluti ...
, with the substance of interest dissolved within. The sample is placed in a cuvette and the cuvette is placed in a spectrophotometer for testing. The cuvette can be made of any material that is transparent in the range of
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...
s used in the test. The smallest cuvettes can hold 70 microliters, while the largest can hold 2.5 milliliters or more. The width determines the length of the light path through the sample, which affects the calculation of the absorbance value. Many cuvettes have a light path of , which simplifies calculation of the coefficient of absorption. Most cuvettes have two transparent sides opposite one another so the spectrophotometer light can pass through, although some tests use
reflection Reflection or reflexion may refer to: Science and technology * Reflection (physics), a common wave phenomenon ** Specular reflection, reflection from a smooth surface *** Mirror image, a reflection in a mirror or in water ** Signal reflection, in ...
so only need a single transparent side. For fluorescence measurements, two more transparent sides, at right angles to those used for the spectrophotometer light, are needed for the excitation light. Some cuvettes have a glass or plastic cap for use with hazardous solutions, or to protect samples from air.


Technique

Scratches on the sides of the cuvette the light passes through scatter light and cause errors. A rubber or plastic rack protects the cuvette from accidentally hitting and being scratched by the machine casing. The solvent and temperature can also affect measurements. Cuvettes to be used in circular dichroism experiments should never be mechanically stressed, as the stress will induce
birefringence Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefring ...
in the quartz and affect measurements. Analyses will perform by using a conventional scanning spectrophotometer and the usual laboratory cuvette (special vial) that fits into the sample cavity of the instrument. Fingerprints and droplets of water disrupt light rays during measurement, so low-lint
gauze Gauze is a thin, translucent fabric with a loose open weave. In technical terms "gauze" is a weave structure in which the weft yarns are arranged in pairs and are crossed before and after each warp yarn keeping the weft firmly in place. ...
or cloth may be used to wipe clean the outer surface of a cuvette before use. Paper towel or similar may scratch the cuvette. Mild
detergent A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more ...
or
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
may be applied, followed by rinsing with tap water. Acid and alkali are avoided due to their corrosive effects on glass, and
acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...
is unsuitable when working with plastic cuvettes. If solution is transferred into a cuvette using a
Pasteur pipette An eye dropper, also called Pasteur pipette or simply dropper, is a device used to transfer small quantities of liquids. They are used in the laboratory and also to dispense small amounts of liquid medicines. A very common use was to dispense e ...
containing air, bubbles may form inside the cuvette, reducing the purity of a solution and scattering light beams. The finger-clad finger method is used to remove bubbles. The solution contained in the cuvette should be high enough to be in the path of the light source. In case the sample needs incubation at a high temperature, care must be taken to avoid temperatures too hot for the cuvette.


Types

Historically, reusable quartz cuvettes were required for measurements in the
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
range, because glass and most plastics absorb ultraviolet light, creating interference. Today there are disposable plastic cuvettes made of specialized plastics that are transparent to ultraviolet light. Glass, plastic and quartz cuvettes are all suitable for measurements made at longer wavelengths, such as in the
visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
range. "Tandem cuvettes" have a glass barrier medium that extends two-thirds of the way up in the middle, so that measurements can be taken with two solutions separated and again when they are mixed. Cuvettes are made from quartz, and plastic (disposable) depending upon UV transmission requirements.


Plastic

Plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
cuvettes are often used in fast spectroscopic
assay An assay is an investigative (analytic) procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity of a ...
s, where high speed is more important than high accuracy. Plastic cuvettes with a usable wavelength range of 380–780  nm (the visible spectrum) may be disposed of after use, preventing contamination from re-use. They are cheap to manufacture and purchase. Disposable cuvettes can be used in some laboratories where the beam light is not high enough to affect the absorption tolerance and consistency of the value. Most often Polymethylmethacrylate (PMMA) and Polystyrene (PS) material use to make the plastic cuvettes.


Glass

Crown glass has an optimal wavelength range of 340–2500 nm. Glass cuvettes are typically for use in the wavelength range of visible light, whereas fused quartz tends to be used for ultraviolet applications.


Quartz

Quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
cells provide more durability than plastic or glass. Quartz excels at transmitting UV light, and can be used for wavelengths ranging from 190 to 2500 nm.


Fused quartz

Fused quartz Fused quartz, fused silica or quartz glass is a glass consisting of almost pure silica (silicon dioxide, SiO2) in amorphous (non-crystalline) form. This differs from all other commercial glasses in which other ingredients are added which change ...
cells are used for wavelengths below 380 nm, i.e.
ultraviolet light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
.


Infrared quartz

IR quartz has a usable wavelength range of 220 to 3,500 nm. It is more resistant to chemical attack from the sample solution than other types designed for fluorescence measurements.


Sapphire

Sapphire Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sapphir ...
cuvettes are the most expensive, though provide the most durable, scratch-resistant, and transmissible material. The transmission extends from UV light to mid-infrared, ranging from 250 to 5,000 nm. Sapphire can withstand the extreme natural condition of some sample solutions and variances in temperature.


History

In 1934,
James Franklin Hyde James Franklin Hyde (born 11 March 1903) was an American chemist and inventor. He has been called the “Father of Silicones” and is credited with the launch of the silicone industry in the 1930s. His most notable contributions include his cre ...
created a combined
silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
cell, which was free from other extraneous elements, as a liquefying technique of other glass products. In the 1950s, Starna Ltd. improved the method to completely melt a segment of glass using heat without deforming its shape. This innovation has altered the production of inert cuvettes without any thermosetting resin. Before the rectangular cuvette was created, ordinary test tubes were used. As innovation motivated changes in technique, cuvettes were constructed to have focal points over ordinary test tubes.


Additional images

File:Measured absorbance of solution filled in a cuvette.jpg, UV-VIS spectrophotometer used with cuvette File:Placing a cuvette in the spectrophotometry machine.jpg, Pointing the clear side of cuvette toward the light source


See also

*
Calibration curve In analytical chemistry, a calibration curve, also known as a standard curve, is a general method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration. ...


References


External links


Spectrophotometry Handbooks

Standard Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near-Infrared Spectrophotometers
{{Laboratory equipment Laboratory glassware