Editing Cuvette

{{Short description|Small container used in laboratories}}
{{About|a tool used in laboratories|the region of the Republic of the Congo| Cuvette Region}}
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[[File:DNS containing solution in a cuvette.jpg|thumb|[[Dansyl chloride]] solution in a cuvette|220x220px]]
In [[laboratory|laboratories]], a '''cuvette''' ({{Langx|fr|cuvette|lit=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]], [[glass]], or [[fused quartz]]. Cuvettes are designed to hold samples for [[Spectroscopy|spectroscopic]] measurement, where a beam of light is passed through the sample within the cuvette to measure the [[absorbance]], [[transmittance]], [[fluorescence spectroscopy|fluorescence]] intensity, [[fluorescence anisotropy|fluorescence polarization]], or fluorescence lifetime of the sample. This measurement is done with a [[Spectrophotometry|spectrophotometer]].

== Overview ==
[[File:2 sizes of cuvette.jpg|alt=A one milliliter and three milliliter cuvette.|thumb|1 mL and 3&nbsp;mL cuvettes]]
Traditional [[ultraviolet–visible spectroscopy]] or [[fluorescence spectroscopy]] uses samples that are liquid.  Often the sample is a [[Solution (chemistry)|solution]], 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]]s used in the test.

The smallest cuvettes can hold 70&nbsp;microliters, while the largest can hold 2.5&nbsp;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 {{convert|10|mm|in|sigfig=2|abbr=on}}, which simplifies calculation of the [[Attenuation coefficient|coefficient of absorption]]. Most cuvettes have two transparent sides opposite one another so the spectrophotometer light can pass through, although some tests use [[Reflection (physics)|reflection]] 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.<ref>{{Cite journal |author=Perkin Elmer Inc. |date=2006 |title=An Introduction to Fluorescence Spectroscopy |journal=Spectroscopy |via=Retrieved 15 August 2013}}</ref> Some cuvettes have a glass or plastic cap for use with hazardous solutions, or to protect samples from air.<ref>{{Cite web |url=http://chemed.chem.purdue.edu/genchem/lab/equipment/spec20/cuvette.html |title=Cleaning and proper use of the cuvettes for the Spec 20 |date=2016-03-17 |website=chemed.chem.purdue.edu}}</ref>

== Technique ==
[[File:A cuvette in a spectrophotometer.jpg|alt=transparent side direct to the light in spectrometer|thumb|A cuvette in a spectrophotometer]]
Scratches on the sides of the cuvette that the light passes through scatter light and cause errors.<ref>{{Cite web |url=http://chemed.chem.purdue.edu/genchem/lab/equipment/spec20/cuvette.html |title=Cuvette |website=chemed.chem.purdue.edu |access-date=2016-03-17}}</ref> 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.<ref>{{Cite web |url=http://www.pharmaguideline.com/2011/05/handling-cleaning-storage-of-cuvettes.html |title=Handling, Cleaning & Storage of Cuvettes of Spectrophotometer |last=Choudhary |first=Ankur |date=2011-09-27 |website=www.pharmaguideline.com |language=en-US |access-date=2017-06-19}}</ref> Cuvettes to be used in [[circular dichroism]]<ref>[http://www.bioch.ox.ac.uk/aspsite/services/equipmentbooking/biophysics/introfluor.pdf Circular Dichroism (CD) Spectroscopy]. Applied Photophysics Ltd., 2011. Retrieved 15 August 2013.</ref> experiments should never be mechanically stressed, as the stress will induce [[birefringence]]<ref>Weisstein, Eric W. [http://scienceworld.wolfram.com/physics/Birefringence.html "Birefringence"]. ''scienceworld.wolfram.com'', Wolfram Research, 1996–2007. Retrieved 15 August 2013.</ref> in the quartz and affect measurements. Analyses are performed by using a conventional scanning spectrophotometer and the usual laboratory cuvette (special vial) that fits into the sample cavity of the instrument.<ref name="ramesh">{{Cite web |last=ramesh |date=2022-11-18 |title=Ultraviolet (UV) Visible Spectroscopy Principle |url=https://pharmaelix.com/ultraviolet-visible-spectroscopy-fundamentals/ |access-date=2022-11-19 |website=PharmaeliX |language=en-US}}</ref>

Fingerprints and droplets of water disrupt light rays during measurement, so low-lint [[gauze]] 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]] or [[ethanol]] may be applied, followed by rinsing with tap water.  Acid and alkali are avoided due to their corrosive effects on glass, and [[acetone]] is unsuitable when working with plastic cuvettes. If solution is transferred into a cuvette using a [[Pipette|Pasteur pipette]] 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.<ref>{{Cite web |url=http://www.cmscientific.com/cuvette_info.php |title=What Is A Cuvette? – How To Use A Cuvette |website=www.cmscientific.com |language=en |access-date=2017-06-19}}</ref> 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]] 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]] 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.<ref name="ramesh"/>

[[File:Cuvette with penny.jpg|thumb|133x133px|A disposable plastic cuvette]]

=== Plastic ===
[[Plastic]] cuvettes are often used in fast spectroscopic [[assay]]s, where high speed is more important than high accuracy. Plastic cuvettes with a usable wavelength range of 380–780&nbsp;[[Nanometer|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 [[Tolerance analysis|absorption tolerance]] and consistency of the value.<ref>{{Cite news |url=http://www.fireflysci.com/news/2015/5/27/guide-to-disposable-cuvettes |title=Guide to Disposable Cuvettes |work=FireflySci Cuvette Shop |access-date=2017-06-21 |language=en-US}}</ref>

Most often Polymethylmethacrylate (PMMA) and Polystyrene (PS) material are used to make the plastic cuvettes.

[[File:Quart cuvette 2.jpg|alt=A quartz cuvette|thumb|Quartz cuvette|177x177px]]
[[File:Cuvette with PTFE Cover.jpg|thumb|221x221px|A UV quartz cuvette]]

=== Glass ===
[[Crown glass (optics)|Crown glass]] has an optimal wavelength range of 340–2500&nbsp;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]] 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&nbsp;nm.<ref name=":0" />

==== Fused quartz ====
[[Fused quartz]] cells are used for wavelengths below 380&nbsp;nm, i.e. [[ultraviolet|ultraviolet light]].

==== Infrared quartz ====
[[Infrared|IR]] quartz has a usable wavelength range of 220 to 3,500&nbsp;nm. It is more resistant to chemical attack from the sample solution than other types designed for fluorescence measurements.<ref name=":1">{{Cite web |url=http://www.precisioncells.com/news/article/30/Difference-Between-Quartz-and-Glass-Cuvettes |title=FireflySci |last=Architects |first=Active Media |website=www.precisioncells.com |access-date=2017-06-23}}</ref>

=== Sapphire ===
[[Sapphire]] 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&nbsp;nm. Sapphire can withstand the extreme natural condition of some sample solutions and variances in temperature.<ref name=":0">{{Cite news |url=http://www.fireflysci.com/news/2015/7/6/how-to-select-cuvettes-for-uv-vis-measurements-cuvette-material-guide |title=How to Select Cuvettes for UV VIS Measurements & Cuvette Material Guide |work=FireflySci Cuvette Shop |access-date=2017-06-21 |language=en-US}}</ref>

== History ==
In 1934, [[James Franklin Hyde]] created a combined [[Silicon dioxide|silica]] 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.<ref>{{Cite news |url=http://www.quartz-cuvette.com/Cuvette_Specifications.html |title=Cuvette Specifications. Transmission Spectra. Spectrophotometer Cells |work=quartz-cuvette |access-date=2017-06-21 |language=en-US}}</ref> 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.{{clarification needed |date=January 2018}}

== Additional images ==
<gallery>
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
</gallery>

== See also ==
* [[Calibration curve]]

== References ==
<references />

== External links ==
{{wiktionary | cuvette}}
{{Commons category|Cuvettes}}
* [http://www.gelifesciences.com/file_source/GELS/Service%20and%20Support/Documents%20and%20Downloads/Handbooks/pdfs/Spectrophotometry.pdf Spectrophotometry Handbooks]
* [http://files.instrument.com.cn/bbs/upfile/200797103147.pdf Standard Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near-Infrared Spectrophotometers]{{Dead link|date=July 2020 |bot=InternetArchiveBot |fix-attempted=yes }}

{{Laboratory equipment}}

[[Category:Laboratory glassware]]