UV vis Cuvette Selection: Cuvette Material and Path Length
Selecting cuvettes for UV vis spectroscopy can be complicated if you are new to the field. Not all cuvette material will work for every experiment, so some basic instruction is required. Using this page as a guide we'll walk you through the important factors you ought to consider when buying a UV vis cuvette.
Cuvette Material Breakdown
The most important factor to consider when finding a suitable cuvette is the cuvette material. There are many types of materials that a cuvette is often made up of. The three hottest cuvette materials are listed below:
- Optical Glass
- UV Quartz
- IR Quartz
Each of these materials has advantages and disadvantages. Again counting on your application will determine which one among the above is the best. Let’s start with optical glass material.
If you've got a limited budget, then you might need to go with a glass cuvette. This cuvette material is great for use in the visible spectral range and features a decent transmission range from 340 - 2,500 nm. Most applications will fall into the range and lots of experiments do not need the extra UV range (190 - 340 nm) that is available with the quartz materials.
UV Quartz can be a step above glass material. Some extra budget is necessary for quartz, but you will furthermore get an extended transmission range of 190 - 2,500 nm. For UV experiments, you absolutely need a UV quartz cuvette and it’s highly recommended not to save budget to this range because by getting a low cost, low quality UV cell, your data will most probably not be up to par.
Next we are going to talk about types of commonly used cuvettes for UV vis applications:
UV vis Cuvettes for Spectrophotometer
The most popular cuvettes for UV vis that we supply are our QL2CR and QL2CF. QL2CR and QL2CF are to some extent identical in terms of material, transmission, usable range and cover. The major difference is that QL2CF cells have square flat bottoms and QL2CR cells have rounded bottoms. Please see the photo below.
QL2CR is the ultimate balance for researchers who are seeking a top quality UV quartz cuvette. You get the complete range of the UV quartz material, plus thanks to the U-shaped bottom, you economize since manufacturing this cell is far easier than the five piece construction of its QL2CF brother. The price for Type QL2CR (CRF Type) only cost a mere $17 making it an excellent choice to buy for labs on a budget.
Fluorescence Cuvettes for UV vis Applications
The QL4HF cell is one of the most commonly used cuvette for UV vis measurements. This cell has all four windows polished and comes within the UV grade quartz. This type of QL4HF cell weighs in at about $37 (CRF Type) dollars, which is way below market price for this cuvette. Unlike our spectrophotometer cuvettes, there's no U-shaped alternative in our fluorescence line.
These types of cuvettes above are most popular standard 10 mm path length cells and there are smaller or longer path length types available. We’ll continue to discuss factors to consider when choosing a proper cuvette.
- What is cuvette path length?
- What are Cuvette Path Length Tolerances?
- What’s Dual-Path Length and how are they used?
- Sample too concentrated, which path lengths to choose?
- Sample too diluted, which cuvette to choose?
What is Cuvette Path Length?
The optical path length of a cuvette is the distance of light that passes through the inside walls of a rectangular cuvette.
The light path or path length of a typical spectrophotometer cuvette is the inner distance from the front window to the rear window of the cuvette clear walls. The standard cuvette path length is 10mm. With a wall thickness of 1.25mm, the standard external sizes of a cuvette is 12.5 x 12.5m, height of 45mm.
10 and 50mm Path Length Cuvettes
Besides standard 10mm spectrometer cuvette path length, the sizes could range from 1mm (even shorter) up to 100mm or longer. Shorter than 1mm light paths are available but those are for more specialized cuvettes such as demountable cells or HPLC flow cells.
0.1mm / 0.2mm / 1mm and 100mm Path Length Cuvettes
Path Length Tolerances
Standard of the spectroscopy industry for cuvette is path length tolerance of ±0.05mm. So in other words, standard 10mm light path length can vary in size from 9.95 mm to 10.05 mm. Or 20mm may range from 19.9mm to 20.1mm.
Cuvettes With Dual-Path Lengths
A series of 4 window clear cuvettes are available in the market which make it possible for short and long path lengths at the same time. For instance, a 0.7mL volume Fluorometer cuvette with a path length of 5 mm and a standard 10 mm all rolled into a single piece.
Dual Path Length Cuvettes Example
Dual-Path Length Cuvette
The optical path length is determined by which side of the dual path length cuvette placed in the spectrometer. For example a 10 x 5mm path lengths cuvette, if the light beam enters the front window, then you can get a 10 mm path length cuvette. If you rotate the cuvette 90 degrees you'll have a 5 mm path length.
Different commonly used dual-path lengths cuvette available such as:
- 10x1 mm
- 10x2 mm
- 10x3 mm
- 10x5 mm
Sample too concentrated, which path lengths to choose?
In the case of high concentrated solutions are available, the possibility to use a 10mm standard cuvette path length for spectrophotometry is diluting the samples. However, there are always samples that couldn’t be possibly or easily diluted. For instance, because of interaction with the solvent, some samples can't be diluted as this may cause a change within the absorbance (i.e. shift within the peak wavelengths)
In these instances when absorbance is high and the dilution of the samples is difficult, "short path length cuvettes" are applicable for utilizing. Short path length cuvettes with optical path lengths of 1mm, 2mm, 3mm and 5mm can be easily purchased. The results obtained by analyzing toluene with a 1mm quartz cuvette and a 10mm ones indicates that there is much less absorption saturation with the 1mm cuvette than there is with the 10mm cell.
A well-known application of short path length cuvette is infrared range spectrophotometry measurement. It could be difficult to obtain the absorption figure of the solution by using a 10mm cuvette under the range of infrared, because of the absorption saturation caused by the sample. A short path length cuvette is used to prevent this kind of saturation due to the sample solvent.
The optical path length of the cuvette is decided based on the size of the absorbance or transmittance of a low or high concentration chemical samples. We’ll continue to discuss solutions for sample too diluted.
Sample too diluted, which cuvette to choose?
The standard 10mm path length cuvettes are most widely used for majority of the solution analysis. However, there are chances that the samples are too diluted and it’s not possible to get enough absorbance by a standard size cuvettes. Of course, the solution can be concentrating the samples, but it is usually difficult in situations that the sample vaporizes or undergoes a chemical change during the process of concentration.
In such cases, a long path length cuvette would be a much easier and more effective solution. Long path length cuvettes with optical path lengths of 20mm, 30mm, 40mm, 50mm and 100mm are available. The absorbance increases proportionately to the cuvettes’ optical path length. Results obtained when 10-mg/L potassium permanganate sample was analyzed with a 10mm cuvette and a 100m one shows that the absorbance of the 100m cuvette is ten times that of the 10mm bottle.
Water turbidity measurement is the most known application when using a long path length cuvette. 50mm and 100mm cuvettes are applied to analyze samples with low turbidity.
Custom Cuvettes for UV vis Measurements
If the cuvettes mentioned above do not suit your requirements, then we've exciting news for you. We will customize any of the many cuvettes from our line to supply exactly what you are looking for. You give us the specs or drawing you need and we’ll look out of manufacturing the cuvette of your dreams.
Now you've got all the essential information to properly choose an excellent cell for UV vis experiments. All that's left to do is add one amongst the above cells to your cart and have us ship you one today.
Here’s to your success!
The iCuvets.Com Team