One of the more important parts of an absorption spectrophotometer system, like the CotsLab portable analyzer, is the cuvettes containing the samples being tested and placed under the light source. Though they may seem straightforward, there’s a lot more to these tubes than meets the eye. You can learn more about them in this guide to spectrophotometer tubes by CotsLab.
Main Spectrophotometer Cuvette Types
Single-Side Cuvettes & Dual-Side Cuvettes: There are two main types of cuvettes for absorption measurements: single-side and dual-side. Single-side cuvettes have one clear side to place your samples, while dual-side cuvettes have two clear sides: one for sample placement and another for receiving light from a spectrophotometer.
Single Side Cuvettes
Many spectrophotometers have cuvettes with a single side, which are a little less common than two-sided cuvettes. If you want to do one of these tests, make sure you’re using clear tubing that’s made for absorbing light – sometimes called UV/VIS tubes. The most common spectrophotometer tubes are made from quartz or borosilicate glass. Both materials can handle higher temperatures than plastic cuvettes (typically 180-300 degrees Fahrenheit), so you don’t need to worry about thermal expansion issues. And some plastic tubes can actually block UV/visible light instead of transmitting it, which is important when testing absorbency.
Double Side Cuvettes
Use double-sided cuvettes when you need to collect a sample in a test tube. If your absorption spectrometer is equipped with an autosampler, then these tubes can be used there as well. Double-sided cuvettes allow maximum sensitivity in light measurement because they have parallel surfaces to focus light efficiently onto sample molecules while blocking any extraneous light. Because of their shape, these tubes also absorb very little of your sample, which means that only 0.5-2% has been wasted after analysis. This saves you time, money, and effort if you need to analyze high volumes of samples; those extra minutes or dollars add up over time!
How Many Sides?
Without getting too technical, there are essentially two types of cuvettes: two-sided and one-sided. In a two-sided cuvette, light can pass through both sides—one of which is clear. Light only passes through one side in a one-sided cuvette—again, which is clear. Both kinds can be used for specific tests, but some tests (namely ones that measure UV/Visible Absorption) require the use of a cuvette with only one side made from a transparent material. One-sided spectrophotometer tubes are becoming more popular because they are easier to clean than their two-sided counterparts. No matter what type you decide on, you want to make sure you’re using reliable equipment, so you get accurate results!
How Thick?: The thickness of your cuvette matters because it directly affects how many times the light will bounce before it leaves your solution. If your cuvette is too thin, then your solution might begin absorbing energy faster than it would have in a thicker glass or plastic specimen container. Keep in mind that an extra thick or large cuvette could lead to problems when measuring small amounts of liquid, so be sure to take into account all potential factors when making your decision! We don’t want you wasting any time with inaccurate absorption readings.
About Absorption Measurements
Like a lot of people, you might have heard that absorption measurements are more accurate than transmittance measurements. That’s only partially true: absorbance is indeed more accurate when measuring pure samples. But there are other variables that can come into play, such as small air bubbles trapped in plastic cuvettes or cellophane (cellulose acetate) membranes if you’re using a handheld spectrophotometer to test cosmetic products, for example. So keep in mind that results will be off slightly if your samples aren’t pure or it’s difficult to achieve total internal reflection within a cuvette. Always use pre-calibrated cuvettes with parallel sides; otherwise, accuracy can range from poor to non-existent.
Other Types of Tests Requiring Special Absorption Cuvettes
Absorption spectrophotometers can be used to help companies determine absorption (how much light is absorbed) by whatever they are testing. It is a valuable tool that all companies should consider, because absorbing more light results in more energy or power. The best cuvettes for absorption measurements have two parallel transparent sides, so the spectrophotometer light is able to pass through, though some special tests require only one single clear side. CotsLab has an excellent selection of spectrophotometers that would make an excellent addition to any company’s arsenal.
To Summarize, cuvettes are essential to absorbance measurements performed with a spectrophotometer. Without them, it is impossible to accurately measure how much light has been absorbed by a sample solution. Cuvettes come in various sizes, and they must be ordered especially; each type of cuvette requires its own type of cuvette tube with customized features. Cuvettes are typically designed with two clear sides so that light is able to pass through for measurement purposes, though some tests may only require one side to be clear.