14 Mar

Cuvettes

Visible spectrophotometers and UV/Visible spectrophotometers are designed for measurement of species in solution by absorption spectrophotometry.  The function of the cuvette is to hold the sample solutions in the path of the light beam.  It is important that these cuvettes be optically clear.  For visible wavelengths glass is used.  Polystyrene or polymethyl methacrylate are used in cases where the reseacher wishes for a disposable cuvette.  If UV wavelengths are being used a quartz cuvette is necesary for transparency.  Brandtech also makes a UV transparent disposable plastic cuvette.  The standard cuvette, both round tubes and square cells, have a 1cm or 10mm inner dimension or path length.   Long path cells are available with 20mm, 50mm and even 100 mm path lengths for very dilute samples.  Short path length cells less than 10mm are also available.  Often only a very small amount of sample is available for measurement; in this case micro cuvettes with sample volumes as low as 50ul are used.  Microcuvettes maintain a 10mm pathlenght despite the small volume.  Other specialty cuvettes include flowcells which allow the cell to be used as part of a continuouse analysis system where the sample is flowing through the cell.

The more sophisticated spectrophotometers allow for specialty cell holders.  Auto cell changers for up to 8 cells are available.  Sipper systems are designed to work with flow cells.  Some manufacturers provide water jacketed or Peltier systems for temperature controll of the spectrophotometer cuvettes.

Robin Prymula