What is cuvette?
is an equipment instrument used for spectroscopic analysis. It is mainly made of quartz powder-fired quartz cuvette
, but also micro cuvette
, semi-micro cuvette
, fluorescent cuvette, and other cuvette.Cuvette
is used to hold the reference solution and sample solution. It usually needs to be matched on spectroscopic analysis instruments, such as a spectrophotometer, bloodline protein analyzer, particle size analyzer, etc. The cuvette is an important accessory of the spectrophotometer, generally rectangular, its bottom and both sides are ground hair glass, the other two sides are made of optical glass bonded to the light-transmitting surface.
Feature of cuvette
a. High mechanical strength. Adapt to temperature changes, the bonding part is very strong, and the pressure resistance can be several atmospheres.
b. Extremely precise optical processing. The optical performance of the transmittance surface is excellent, and the grouping error is ≤0.3%.
c. Choose high-quality quartz glass and optical glass to ensure no bubbles and no streaks. Quartz cuvette is greater than 80% at wavelength 200nm, while glass cuvette is greater than 80% at wavelength 340nm.
Glass cuvette vs. quartz cuvette
There are two manufacturing processes for cuvettes, one is adhesive bonding and the other is high-temperature fusing. The materials used for cuvettes are usually derived from quartz, fused silica, and optical glass. Commercially available cuvettes are square, rectangular, and cylindrical in shape and generally have a capacity of a few milliliters. There are also miniature or ultra-miniature capillary dishes for small amounts of specimens. In addition, there are high and low-temperature cuvettes.
The cuvettes are divided into visible series (called glass cuvettes), UV-visible series (called quartz cuvettes), and infrared series (called infrared quartz cuvettes) according to the wavelength range used. The cuvettes used in the UV photometric experiments are glass cuvettes and quartz cuvettes. Glass cuvette is made of optical glass cuvette, and can only be used in the visible region, for 330 ~ 1000nm wavelength range; quartz cuvette is made of fused silica (silicon oxide) cuvette, both for the ultraviolet region, can also be used in the visible region, for 200 ~ 400nm wavelength range. Using the difference between quartz and glass cuvettes with and without absorption in the UV region and visible region, when in the UV region, as the glass cuvette strongly absorbs UV light, it has an effect on the experimental data and results, while the quartz cuvette does not absorb UV light and does not affect the data, so instead of using glass cuvettes in the UV region, quartz cuvettes are used. And in the visible region, the influence of glass is very small, negligible, and quartz cuvettes can be used as well. However, considering the economic saving factor, as the price of glass cuvette is much lower than quartz cuvette, usually choose to use glass cuvette in visible region and quartz cuvette in UV region.
Identification of cuvette
A. Intuitive method
Different sensory methods of visual and auditory observation and comparison of the appearance and clarity of cuvettes are used to identify them.
a. The cuvette is usually marked with a letter, "G" (Glass) at the mouth of the glass cuvette and "Q" (Quartz) or "QS /S" (Quartz Glass) at the mouth of the quartz cuvette. ".
b. If there is no letter mark or the mark is worn, you can look at the mouth edge from top to bottom, and if the prismatic surface is greenish it is glass, transparent or white it is quartz. To be more precise, the break of ordinary glass is light green, the break of boric acid glass is white, and the break of quartz is transparent.
c. You can listen to the sound to identify. The sound of quartz tapping is relatively crisp; the sound of glassware tapping is muffled.
d. Quartz is harder than glass, if the two cuvettes grinding, quartz cuvette wear tiny, while the glass cuvette wear is relatively large.
e. Available incandescent light, high transmittance is the glass cuvette, while the quartz cuvette should be slightly cloudy inside.
Now the preparation process is superb, both glass cuvettes or quartz cuvettes are clarified and transparent in appearance, and the difference in thickness and quality is not significant, so the identification method by intuition alone is not desirable.
B. Machine testing method
Use UV-Vis spectrophotometer to identify glass, quartz cuvettes and paired cuvettes. Quartz cuvette should have absorbance less than 0.07abs at 250nm, if absorbance is greater than 0.07abs then it is a glass cuvette.
No sample is placed inside the cuvette, and the wavelength is set to 250nm with air as the medium and zeroed. Place the cuvette in the sample path, the absorbance value less than 0.07abs is quartz cuvette, and vice versa is glass cuvette.
Use of cuvette
When using the cuvette, the two light-transmitting surfaces should be completely parallel and placed vertically in the cuvette holder to ensure that the incident light is perpendicular to the light-transmitting surface when measuring, avoiding the loss of light reflection and ensuring the light range is fixed.
The cuvette is generally rectangular, the bottom and both sides of the ground glass, the other two sides of the optical glass made of a light-transmitting surface using fused together, glass powder high-temperature sintering, and glue bonding. So, when using the following points should be noted.
a. When picking up the cuvette, the operator should only touch the hairy glass on both sides with his fingers to avoid touching the optical surface. At the same time, pay attention to lightly holding and placing to prevent breakage.
b. The cuvette should not hold solutions containing corrosive glass substances for a long time.
c. The cuvette is easy to burst after high temperatures, so it should not be heated on the flame or electric stove or baked in the drying oven.
d. When the inside of the cuvette is contaminated, it should be cleaned with anhydrous ethanol and dried or wiped clean in time.
e. The light-transmitting surface of the cuvette should not be in contact with hard or dirty objects.
f. When holding the solution, the height should be at 2 /3 of the cuvette, the optical surface with residual liquid can be gently adsorbed with filter paper, and then wipe with lens paper or silk.
g. The liquid in the cuvette should be tilted along the gross surface and poured off slowly, do not turn the cuvette over, and place it directly mouth down on a clean filter paper to absorb the remaining liquid. Then rinse the cuvette inside with distilled water and pour it off (operation as above) to avoid liquid outflow, so that the 2nd measurement without wiping the cuvette, without the error brought about by wiping.
h. Before colorimetric measurement, the operator needs to fill each cuvette with distilled water. Compare the colorimetric wavelength, and select 4-8 cuvettes with the error within ±0.001 absorbance for colorimetric determination, which can avoid the measurement error caused by the difference of cuvettes.
i. The cuvette should be rinsed clean with water immediately after use. If necessary, soak in 1:1 hydrochloric acid, and then rinse with water.
Precaution of cuvette
a. When picking up the cuvette, only touch the hairy glass on both sides with your fingers and avoid touching the optical surface.
b. The optical surface should not be in contact with hard or dirty objects. When holding the solution, 2/3 of the cuvette height can be, and the optical surface of any residual liquid can be gently adsorbed with filter paper, and then wipe with lens paper or silk in the same direction.
c. Any solution containing substances that corrode the glass should not be placed in the cuvette for a long time.
d. The cuvette should not be put on the flame or electric stove for heating or baking in the drying oven.
e. If you have doubts about the cuvette during the measurement, you can test it by yourself. Can choose the wavelength in the actual use of wavelength, a set of cuvettes are filled with distilled water, one of the transmission ratio to 95% (digital display instrument set at 100%), measurement of the transmission ratio of the other, where the difference in transmission ratio is not greater than 0.5% can be used with.
f. The error after cuvette reversal can be about 4%-7%. So in the precise measurement, the operator must look at the cuvette arrow mark. If there is no sign, can be made after supporting the calibration in the direction of the upper end of the wool glass for the arrow consistent mark. To avoid the operation of the reverse.
g. Please do not collide with the cuvette when using.
How to buy cuvette?
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