cuvette

A cuvette is a small, transparent container used to hold liquid samples in optical experiments, most commonly in spectrophotometry. The term comes from the French cuvette, meaning a small cup or basin. Cuvettes are designed to allow light to pass through the sample with minimal interference, so the material and surface quality are important for accurate measurements.

Cuvettes are typically made from optical-grade plastic, glass, or quartz. Plastic cuvettes (such as polystyrene, PMMA, or cyclic olefin copolymers) are inexpensive and suitable for visible light, but can be less stable with certain solvents or at UV wavelengths. Quartz or fused-silica cuvettes offer high UV transparency and are used for measurements below about 320 nm. Glass cuvettes are common for visible light work but are generally unsuitable for UV measurements. The outer design is usually square-edged or square-shaped to ensure consistent alignment in the instrument.

Most standard cuvettes have a light path length of 1 centimeter (10 millimeters), defined by the distance between two optically clear faces. Shorter-path variants (for higher concentration samples) and specialized microcuvettes with smaller volumes are also available for particular instruments and applications.

Handling and cleaning are important to prevent measurement errors. Cuvettes should be kept clean, free of fingerprints, scratches, and residues on the optical surfaces. Cleaning depends on material and solvents used; plastic cuvettes may be damaged by aggressive solvents, while glass and quartz cuvettes require gentle washing and drying with lint-free tissues.

Applications include UV–visible spectrophotometry, colorimetric assays, enzyme kinetics, and other optical analyses where absorbance or transmittance of light by a liquid sample is measured.