Cuvettes in a spectrophotometer must be held in exactly the correct position relative to the light beam – this is the job of the cuvette holder or cell holder. Cell holders are specific to the spectrophotometer brand and can take many forms. The standard cell holders hold round and/or square 1cm cuvettes. Any round or square 1cm cuvette from any manufacturer should fit in the standard cell holders.
Multiple cell holders can be manual or automatic; they can be in the form or a carousel or linear. As with the standard single cuvette holders any standard 1cm square cuvettes should fit multiple cell holders.
Many manufacturers offer temperature controlled cell holders. These can be water jacketed or Peltier; these also should be able to hold any 1cm cuvette.
Flow cells require a sipper cell holder. These sipper units have a controller and a pump for moving sample through the flow cell. Some sipper units are also temperature controlled. Flow cells my be specific to the sipper accessory.
Micro-cuvettes present special problems, the cell holder must hold the micro cuvette at just the right height so the light beam passes through the sample. The beam height can be determined for the spectrophotometer and it is important the the microcuvette beam height matches the instrument beam height. Some manufacturers such as Unico offer a cell holder which can adjust the height of the micro cuvette.
If you are using standard 1cm cuvettes, any cuvette should fit in any standard holder no matter who the manufacturer is. For microcuvettes and flow cells you may have to go to the manufacturer of the spectrophotometer for the correct cuvette.