Overview

A cuvette is a small, usually rectangular or cylindrical, container designed to hold liquid or sometimes solid samples during optical measurements. It is an essential accessory in instruments that measure how a sample transmits, absorbs, or emits light, such as spectrophotometers and fluorometers. The name derives from the French word for a small tub or cup; in laboratory contexts a cuvette is often called a sample cell or optical cell.

Design and materials

Cuvettes are made from materials selected for their optical clarity and transparency in the wavelength range of interest. Common materials include plastics for routine visible-range work, borosilicate or other optical glasses for general-purpose use, and high-purity optical quartz or fused silica where ultraviolet transparency and low absorption are required. Manufacturers polish two opposite faces to form optical windows so light can pass through the sample with minimal scattering or reflection.

  • Plastic — inexpensive, often disposable, useful for visible-range assays; see plastic cuvettes.
  • Glass — durable and affordable for many applications; related information at glass.
  • Quartz / fused silica — required for ultraviolet measurements; referenced at optical quartz.

Common types and features

Cuvettes vary by volume, pathlength and geometry. Pathlength — the distance light travels through the sample — is often 1 cm for standard analytical methods, but shorter or longer pathlengths are available to accommodate very concentrated or very dilute samples. Geometry includes square or rectangular cells (preferred for precise optical alignment) and round ones (sometimes used where orientation is not critical). Caps, stoppers, or screw tops allow sealing to prevent evaporation or contamination.

Uses, handling and best practice

Cuvettes are used in absorbance and transmittance measurements, fluorescence assays, kinetic studies, and clinical analyzers. Instruments rely on the Beer–Lambert relationship between absorbance and concentration, so cuvette cleanliness and consistent pathlength are essential for reliable results. Handle cuvettes by their frosted or non-optical sides to avoid fingerprints on optical windows; rinse and, when needed, polish or sonicate to remove residues. Align the cuvette correctly in the instrument so the transparent faces are parallel to the light path.

  • Always match cuvette type to wavelength range and chemical compatibility.
  • Keep optical surfaces clean and dry; avoid solvents that can etch certain plastics.
  • Use caps to reduce evaporation and prevent bubbles, which can scatter light.

History, terminology and distinctions

The cuvette became a standard laboratory accessory with the development of quantitative optical spectroscopy in the late 19th and early 20th centuries as instruments and photometric methods matured. In everyday lab language a cuvette resembles a small test tube in purpose but differs in its polished optical windows and standardized pathlength; compare general-purpose glassware at laboratory glassware and the classic test tube. The term "sample cell" or "optical cell" is also used, especially when referring to specialized flow-through or temperature-controlled variants used in research instruments.

For more on the measurement techniques that use cuvettes, see introductory material about spectroscopy. Manufacturers and suppliers provide detailed specifications for pathlength, material transmission ranges, usable volumes, and recommended cleaning procedures.