Cuvetten

Cuvetten are small, transparent containers used in laboratory optical measurements to hold liquid samples. They are designed to allow light to pass through the sample with minimal distortion, making them essential for spectrophotometry, colorimetric assays, and related analyses. The most important specification is the optical path length, commonly 1 centimeter, though other lengths such as 0.5 cm or 2 cm are available for different measurement ranges.

Materials vary by application. Glass and borosilicate glass cuvettes are common for visible light, while quartz cuvettes are required for ultraviolet (UV) measurements due to their higher UV transmittance. Plastic cuvettes, often made from polystyrene or polymethyl methacrylate, are inexpensive and disposable but generally have more limited UV compatibility and may exhibit higher optical variability due to manufacturing tolerances or sorption effects. Cuvettes typically have two opposite faces that are optically polished and parallel to ensure a clean light path; some designs are square in cross-section to minimize internal reflections, while others are round.

Handling and maintenance are important for accuracy. Cuvettes should be held by the edges or ends to avoid fingerprints on the optical faces, and cleaning with distilled water or appropriate solvents is recommended to remove residues. Scratches, chips, or residue can affect absorbance readings and must be avoided. They are placed in a spectrophotometer’s sample holder with proper orientation and filled to the recommended level to minimize bubbles and stray light.

Beyond laboratory use, the term cuvette in general language refers to a small basin or bowl in French, and the word also appears in geographic names. See also spectrophotometry and Beer's law.