Cuvettes fused silica

Optical Applications. Vitreous silica is ideal for many optical applications because of its excellent ultraviolet transmission, resistance to radiation darkening, optical polishing properties, and physical and chemical stability. It is used for prisms, lenses, cells, windows, and other optical components where ultraviolet transmission is critical. Cuvettes used in scatter and spectrophotometer cells are manufactured from fused silica and fused quartz because of the transmissive properties and high purity (222). 

Glass cuvettes are the least expensive but, because they absorb UV light, they can be used only above 340 nm. Quartz or fused silica cuvettes may be used throughout the UV and visible regions ( 200-800 nm). Disposable cuvettes are now commercially available in polymethacrylate (280-... 

Sample containers, which are usually called cells or cuvettes, must have windows that are transparent in the spectral region of interest. Thus, as shown in Figure 25-2, quartz or fused silica is required for the UV region (wavelengths less than 350... 

The excitation source is often a xenon arc lamp with a power of 150 to 800 watts. The measurement of the light intensity is carried out using a photomultiplier tube or a photodiode. The solvent, the temperature, the pH and the concentration are the principal parameters which affect the intensity of fluorescence. For solution samples, rectangular 1 cm glass or fused silica cuvettes are used. 

The cells or cuvettes (also spelled cuvets) used in UV absorption or emission spectroscopy must be transparent to UV radiation. The most common materials used are quartz and fused silica. Quartz and fused silica are also chemically inert to most solvents, which make them sturdy and dependable in use. Note Solutions containing hydrofluoric acid or very strong bases, such as concentrated NaOH should never be used in these cells. Such solutions will etch the cell surfaces, making them useless for quantitative work.) Quartz and fused silica cells are also transparent in the visible and into the NIR region, so these could be used for all work in the UV and visible regions. These are also the most expensive cells, so if only the visible portion of the spectrum is to be used, there are cheaper cell materials available. 

In practice, most fluorescence measurements are taken in solution and 1 cm glass or fused silica cuvettes with four polished windows are used. For some specialized applications different types of cuvettes are commercially available. For example, flow cells of different configurations for continuous flow spec-trofluorimetric analysis have been designed. 

Fused silica (UV grade) has excellent transmittance properties and is both durable and thermally stable. It finds uses as the material of choice for prisms, lenses, windows and cuvettes in the region 160-2000 nm. However, infrared grade fused silica may be used from 250 to 3500 nm. Optical crown glasses are more restricted in wavelength range from 300 to 2500 run. 

Our single-molecule detector is based on the sheath-flow technology introduced by Keller s group. A 10 pm inner diameter, 142 pm outer diameter, and 29 cm long fused silica capillary is introduced into the flow chamber of a sheath flow cuvette [40]. The volume contained within this capillary is about 25 nL. The locally constructed sheath flow cuvette has 1-mm thick quartz windows and a 150 pm square flow chamber. The flow chamber is held within a stainless steel holder that is held at ground potential. Buffer is introduced into the cuvette, drawing analyte from the tip of the capillary as a fine stream in the center of the flow chamber. 

The sample cells used in fluorescence spectroscopy have all four sides dear, since in most instruments the fluorescence photons are detected at an angle of 90° to the propagation direction of the exdtation beam. The 90° geometry is used in order to minimize any interference in the fluorescence hght detection by the exdtation light beam. In most cases the cuvettes are made from fused silica (quartz) but if the exdtation and fluorescence wavelengths are above 300 nm plastic disposable cuvettes may be used. 

Here it is important to use either a quartz or fused silica cuvette due to the properties of DMF. 

There is a large range of optical cells available for spectroscopy measurements and they vary in materials, size, shape, and spectral transmission characteristics. The most commonly used sample holder in fluorescence spectroscopy is a 10 mm x 10 mm x 45 mm volume cuvette made from fused silica (for UV to near-lR operation), glass (visible), or a plastic that is often polycarbonate and disposable. Of course, it is essential that the cuvette chosen is suitable for the application and experiment and that it is clean, and handled with maximum care. 

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