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A cuvette (from French cuvette = "little vessel") is a small tube of circular or square cross section, sealed at one end, made of plastic, glass, or fused quartz (for UV light) and designed to hold samples for spectroscopic experiments. Some cuvettes will be clear only on opposite sides, so that they pass a single beam of light through that pair of sides; often the unclear sides have ridges or are rough to allow easy handling. Cuvettes to be used in fluorescence spectroscopy must be clear on all four sides because fluorescence is measured at a right-angle to the beam path to limit contributions from beam itself. Some cuvettes, known as tandem cuvettes, have a glass barrier that extends 2/3 up inside, so that measurements can be taken with two solutions separated, and again when they are mixed. Typically, cuvettes are 10 mm across, to allow for easy calculations of coefficients of absorption. A cuvette may have a glass or Telfon cap to cover on the top or may open to the atmosphere. To measure the sample, the transparent side must be placed toward the light in spectrophotometer. For accurate measurement, these testing tubes should be cleaned and without any scratches. Cuvettes to be used in circular dichroism experiments should never be mechanically stressed, as the stress will induce birefringence in the quartz and affect the measurements made.

Nomenclature
Tests for UV/Vis spectrophotometry are frequently require samples in a fluid form, in spite of the fact that the absorbance of gasses and even of solids can likewise be measured. Samples are normally set in a transparent cell container, known as a cuvette. Cuvettes are regularly rectangular fit, generally with an inner width of 1 cm. (This width turns into the way length, L, in the Beer-Lambert law.) Test tubes can be replaced for cuvettes in some proper experiments. The best cuvettes are made of specified quartz, but glass or plastic cuvettes are more common in the normal laboratory. For the experiment, which require an accuracy in data analysis of absorption and reflection of wavelength, glass and most plastics may limit the UV, which may constrains the ability of acute wavelength that can be absorbed.

History
A few people in the past misunderstood that technicians burrow out a solid block of quartz to make a cuvette, however this is an incorrect conception. Corning chemist J. Franklin Hyde made combined silica in 1934 from liquid chemicals, which is free of extraneous elements instead of liquefying dry mineral fixings like other glass type products. In the 1950s, the establishing individuals from Starna Ltd. in the UK created and idealized the method of completely melding optically cleaned segment parts by using only heat, and without deformation of its shape. This creation altered the production of completely inert cuvettes without any pastes or thermosetting resin, also provide exacting dimensional and optical resiliences. Before rectangular cuvettes were created, researchers use standard test tubes for their examinations. As innovation enhanced and strategies were found to paste and fire intertwine glass plates, the techniques changed. Cuvettes had a huge amount of focal points over utilizing test tubes. When utilizing a cuvette with flat optical walls, there is zero chance of light to scatter everywhere of the surface as when it will hit a round surface instead. Moreover, it is considerably less difficulty to get a nice uniform complete when cleaning flat plates. This gives the plates a nice even thickness approximate within a resistance of +/ - 0.02 mm. Round surfaces require a fire polish to enhance optically clear. This polish can twist the glass or quartz and give incorrect readings.

Types of cuvettes
The standard glass cuvettes and UV cuvettes for spectrophotometers and fluorometers come with different supported wavelength, materials, and the matching tolerance in the unit of nanometer, which consequently have different techniques to measure the reflection and absorbance of light. Inexpensive cuvettes have a round shape similar to test tubes. Cuvettes to be used in circular dichroism experiments should never be mechanically stressed, as the stress will induce polarization of the glass and affect the measurements made. Choosing suitable cuvettes for UV-VIS can be complicated since there are a few materials of cuvette, which will work for various motivation behind the investigation. Some essential instruction is required to consider critical elements while choosing an UV-VIS cuvette. For UV spectrophotometers, quartz cuvettes are considered as the standard since these synthetic materials can be produced into semi-smaller and miniaturized scale cuvettes for a small specimen. There is some cautious considerations while picking small-scale cuvettes since the signal transmitted beam of the spectrophotometer can not be lower than the beam height determined by the cuvette maker. Long way length cuvettes, rectangular and barrel shaped, are accessible for extremely diluted solution tests. For fluorescent measuring, cuvettes must be optically transparent on all sides. Some basic education is required to consider important factors when selecting a UV-VIS cuvette. There are several different types of cuvettes commonly used; each type has different usable wavelengths at which its transparency exceeds 80%:

Disposable plastic cuvette

Disposable plastic cuvette is one of the most cheapest types, while it is not as clearly transparent as quartz or glassware materials. The plastic cuvettes are often used in fast spectroscopic measurement, which considered speed rather than accuracy of the assay. Plastic, with a wavelength from 380 to 780 nm (visible spectrum). Plastic cuvettes are accessible for obvious, UV, and fluorometry. This type of cuvettes are useful since it can be disposed into waste and relatively low in price, which still can be used in some experiment, where high throughput of light and the absorption tolerance is not high enough to affect the accuracy of the test.

Glass cuvettes

Glass cuvettes are typically for use in the wavelength range of visible light and fused quartz tends to be used in the UV through NIR ranges. Optical Glass, has an optical wavelength range of 340-2,500nm in which it transmits over 80% along with a matching tolerance of 1% at 350nm.

Quartz cells and others

The other types of cuvettes are more expensive than the plastic cuvette. It is disposable and will be eliminated once complete the spectrometric experiment to prevent risk from reusing cuvettes and damaging expensive quartz. Quartz cells considered to have more durability compared with plastic and can be reused many times, while proper care and cleaning is consistent. Quartz has better ability in the UV, providing a useable range of wavelength around 170-2700 nm. Color and UV range can be analyzed by this type of cuvette. The smallest one are capable of holding 70µl, the medium size contains between 1.5ml and 3.0ml, and the biggest is for testing samples with 2.5ml or larger.

Fused quartz and fused silica are assortments of glass containing principally silica in indistinct (non-crystalline) type. They are made by numerous distinct procedures, in which glasses framed by the customary 'dissolve extinguish' strategies (warming the substance to liquefying temperatures, then quickly cooling to the strong glass stage), are frequently alluded to as 'vitreous', as in 'melt-quench' technique. To elaborate, it is a heating method to melting temperatures and rapidly cool down temperature to make the glass turn into a solid phase. It is often called "vitreous silica" since term 'vitreous' in glass referred when utilized an amorphous solid material insides the melt-quench context.

Fused quartz, with a wavelength below 380 nm (ultraviolet spectrum), is fabricated by melting normally quartz crystals of expansive purity at roughly 2000 °C, working with either an electrical fused heater or a oxygen-fuelled fusion. Fused quartz is typically crystal clear. The optical properties of combined quartz are better than those different sorts of glass due to its purity.
 * UV quartz has an operational wavelength available in a range of 190-2,500 nm for UV light and a matching tolerance is 1% at 220 nm.
 * ES quartz has a usable wavelength range of 190 to 2,000 nm, and a matching tolerance of 1% at 220 nm. Precision cell cuvettes are example of synthetic fused silica or ES quartz.
 * IR quartz, used of highly pure artificial material called ED-C quartz, has a usable wavelength range of 220 to 3,500 nm, and a matching tolerance of 1% at 2,730 nm.

Consideration of cuvettes
The cuvette is accumulated with both quantitative and qualitative measurement of a solution. Using a cuvette with the spectrophotometer depends on the expected result as there are two main measurements, including the UV-Vis and fluorescence spectrophotometer. Types of cuvette altered as the radiation of certain kind of spectrometer used. In case, the experiment is performed to find absorption value; a cell with two optically transparent polished windows is used to fill the sample solution. The light with an approximate limit of settle wavelength enters the cell through the cell in a straight line. The light that is absorbed is directly proportional to the concentration of sample solution. Otherwise, fluorescence measurement uses different wavelength as solutions can absorb penetrated light at at a higher wavelength. The concentration of fluorimetry is observed from three to six log orders, in which the modification or dilution of the sample is not required. The cell used has three alternately four polished windows instead of two because both an excitation and emission spectrum can be measured.

Cuvette calibration
The cuvette calibration has a great effect on the absorbance measurement. Many variables need to be considered to make the adjustment as precise and accurate. Cleaning the cuvette and centering a tip of the pipette for drawing solutions are concerned when performing the adjustment. All four inner sides of the cuvette are relentlessly rinsed with the solution that is measured. The spectrophotometric measurement is sensitive to the change in volume. The calibration cuvette helps scientists to convert the volume data from relative value units to the true volume with the less uncertainty. The cuvette adjustment is important for laboratory technicians who acquiring a precise estimation of the volume of solution.

In the laboratory facility, sometimes a round glass cuvette is frequently utilized. The adjusted cuvette that has been aligned and sold in the market is expensive contrasted with the cost of normal glass tubes. The glass cell costs approximately 30 times higher than an ordinary glass tube. In turn, the cuvettes do the most appropriate sort of spectrophotometer, but in the some researches need the great number of cuvette and can be costly. A great quality glass tube, Pyrex, as calibrated it gives similar result as a cuvette. However, the manually calibrated cuvette has less consistency. The adjustment and position of the tube affect the reading value of the absorbance as the light goes through the sample controlled by the width of the cuvette. The distance traveled by light and the concentration of solution influence the estimation of absorbance. The appropriate wavelength and type of cuvette is the main component for measuring the correct absorbance with manually calibrating the cuvette.

Standard Technique
There is some possible source of errors and stress factors, which induces the expected measurement. Erroneousness in the spectrophotometer such as light distribution occurs when light hits the scratched cuvette. Rubber or plastic rack protects the cuvette from accidentally hit or scratch from an aluminum during the experiment. Types of solvent used, temperature, and the wavelength of the light affect the measurement at different level of light transmitted through the cuvette.[20]

Gauze or tissue paper is used to wipe the outer surface of the cuvette as a solution is drawn in the cuvette. Protein from fingerprints or droplets of water disrupt the reflection of light rays during the measurement. In case the pasture pipette contains air during transfer the solution, bubbles inside the cuvette reduce the purity of a solution and cause light beams to be more scattered. Finger-clad finger method is used to remove bubbles. The solution contained in the cuvette matches at least high or higher than the slit through and the grip whereby the light source is transmitted through.[21]

Mild detergent and ethanol rinsing with tap water is used to wipe off the outer layer of the cuvette. Acid or alkaline is not tolerated to the material of cuvette. These corrosive liquids erode the glass and make the cuvette skin smooth damaged. A soft cloth washing material prevents scratching the surface of cuvette, unlike a tube cleaning brush; it cuts the surface of cuvette. In case, the cuvette needs incubation for specific condition of the experiment, temperature of 100 ℃ and above is not permitted as a high level of temperature affects the surface of cuvette.[22]