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Introduction
Any material that is transparent to the required wavelengths can be used to make a cuvette. And a wide selection of cuvette volume is available. The sub-micro cuvettes can be as small as 10 microliters (or less), while the macro types can hold up to 35 milliliters (or more).
Any material that is transparent to the required wavelengths can be used to make a cuvette. And a wide selection of cuvette volume is available. The sub-micro cuvettes can be as small as 10 microliters (or less), while the macro types can hold up to 35 milliliters (or more).
The length of light passing through the cuvettes containing sample solutions is called path length, which has an effect on the absorbance value calculation. Many cuvettes have a standard light path of 10 mm (0.39 in), which makes the calculation of the absorption coefficient easier.
10mm Path Length Cuvettes
Most 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. For fluorescence sample measurements, two parallel clear sides and additional right angles sidewalls clear are also necessary for the excitation light. PTFE caps, stoppers, or screw caps are used with hazardous or evaporative solutions to protect samples from the air.
It can be complicated and confusing if you are new to the field of selecting cuvettes for UV-vis spectroscopy. Not all cuvettes work for every application, and some basic knowledge is useful to make the decision. The article will help you walk through the most important factors to consider when making a final decision.
How do you define a cuvette?
A cuvette (French: cuvette = “little vessel”) is a small tube-like container with straight sides and a circular or square cross-section. They’re normally sealed on one end and have a cap to seal the other.
To prevent refraction artifacts, regular types of cuvettes have a square or rectangular cross-section. The majority of the cuvettes are used in spectrophotometers, colorimeters, and fluorometers.
A cuvettes is a small glass/quartz/plastic lab vial which is used to hold solutions (or powder in some circumstances) for spectroscopic experiments. When a light beam passes through the sample within the cuvette, the absorbance, fluorescence intensity, transmittance, fluorescence polarization, or sample fluorescence lifetime are measured. The testing of measurement is performed with a spectrophotometer.
Simple Spectrophotometer Design
The materials available for cuvettes are optical glass, plastic (PMMA or PS), UV quartz and IR quartz. The plastic cuvettes are much less expensive than quartz materials thus they can be used as disposable to avoid cross contamination in fast spectroscopic assays. Quartz or glass cuvettes are necessary for organic and corrosive sample solutions. Generally speaking, glass or quartz cuvettes have a higher transmission rate and accuracy of data compared with plastic materials, and these materials of cuvettes can be reused many times if properly used.
Quartz with Q, Glass with G, and Plastic cuvettes
Understanding Cuvette Path Length
The cuvette path length is the distance at which light travels through the inside walls of a rectangular cuvette. A typical spectrophotometer cuvette path length is the inner length between two clear parallel walls. The standard and most used path length is 10mm. And the cuvette’s most common exterior dimension is 12.5 x 12.5mm, with a height of 45mm, which makes the wall thickness of 1.25mm.
12.5×12.5 mm External Cuvettes
Besides 10mm standard cuvette path length, shorter path lengths (from 0.1mm) and longer types (up to 100mm or longer) are also available for different volume sizes. We’ll discuss in more detail below.
Optical Path Lengths Vary from 0.1 – 100mm
Tolerances for Path Length
Our cuvettes are manufactured with a path length tolerance of ±0.05mm. In other words, the 10mm standard cuvette can vary in path lengths between 9.95 – 10.05 mm. Or for 20mm cuvettes, the path length could be from 19.9mm to 20.1mm.
Dual Optical Path Length Cuvettes
With a dual path length cuvette, it’s possible to have both short and long path lengths in the same cuvette cell at the same time. For example, a 1mL size 4 clear walls cuvette can have dual path lengths of 3mm and 10mm in the same cell.
You can decide which path length to be used for a dual path cuvette by placing different sides in the spectrophotometer / fluorometer. For instance, a 10 x 3 mm dual path cuvette, if the light source passes through the small window, the path length is 10 mm and if light passes the bigger window (rotate 90 degrees), the path lengths will be 3 mm.
Different commonly used dual-path lengths cuvette available such as:
A variety of commonly used dual-path cuvette are available with us:
- 2 x 10 mm
- 5 x 10 mm
- 10 x 20 mm
- 10 x 50 mm
Dual-Path Lengths Cuvettes
Types of Cuvette Materials
Previously, reusable quartz cuvettes were necessary for measurements in the ultraviolete (UV) range, because most plastics and optical glass materials absorb the ultraviolet light, resulting in interference. Now a few types of specialized plastic cuvettes are also transparent to UV light ranges. Optical Glass, plastic and all quartz material cuvettes are transparent to visible light ranges.
Quartz Material is Transparent to UV but Glass is not
As the most prominent factor to consider when choosing a suitable cuvette is the material, we are going to compare these materials in more detail below:
- Optical Glass
- UV Quartz
- IR Quartz
- Plastic
While each of these materials has some advantages, it also has some disadvantages. Again counting on your experiment requirements, you should decide which of the materials are the best. Let’s start with optical glass material.
Optical Glass
Optical glass material cuvettes are a good choice if you have a tight budget and the desired wavelength range is visible spectral (340 – 2500 nm). The material also has a decent transmission rate of >80% at 350nm. Most measurements will fall into this area and it’s not necessarily required to have the extra UV quartz material range (190 – 340 nm) for lots of applications.
Types of Glass Cuvettes
UV/ES Quartz
Another option is UV quartz, which is a step above glass material. If you got some extra budget, UV quartz material would be a nice choice that you can get a measurement transmission range of 190 – 2500 nm. If you are performing UV experiments, a UV quartz cuvettes would be an absolute need and it’s important not to cut cost to this range as the data will most likely not be up to par if the choice is a low cost, low quality UV cuvette cell. ES quartz glass material has a higher transmission rate than UV quartz material, which is used on our All Fused or High Transmission types of cuvettes and cells.