Cuvettes

Depending on the instrument, spectrophotometers take measurements at one of three optical-beam light heights (the distance from the bottom of the cuvette, also know as Z dimension or light height): 8.5, 15 or 20 mm. Most spectrophotometers will accept macro cuvettes since they have a straight wall. Micro cuvettes, on the other hand, have the same outer footprint as standard cuvettes, but their interiors are generally tapered to limit the quantity of sample material necessary. The standard cuvette, on the other hand, is intended to measure through the sample at a particular light height in the chamber. It’s critical to double-check that the cuvette Z dimension you use to measure your sample is compatible with your instrument’s light height. Consider the following key characteristics of cuvettes:

1. When measuring materials with low concentrations, such as RNA, single-stranded DNA, and oligonucleotides, you’ll need a long enough path length to keep the values within the instrument’s linear measurement range. Although some cuvettes now on the market allow an alternate path length, the standard size is 10 mm. Some dual path length cuvettes may be turned 90 degrees for a reading at a another path length.
2. It’s recommended to use a sterile, disposable plastic cuvette if you want to retrieve your sample after a measurement. Although bulk cuvettes are available, some applications may need individually wrapped, sterile cuvettes that are certified protein-free or nuclease-free.
3. The absorbance of a sample at a wavelength of 600 nm, usually referred to as the “OD600,” is used to estimate the concentration of a bacterial culture. A macro cuvette’s greater sample capacity allows heterogeneous samples like these to produce a more accurate readout.