Cuvette Specifications

History of Cuvettes
Corning chemist J. Franklin Hyde made fused silica in 1934 from pure liquid chemicals instead of melting dry mineral ingredients like other glass products. During the 1950s, the founding members of Starna Ltd. in the UK developed and perfected the technique of fully fusing optically polished component parts by heat alone, without distortion. This enabled production of fully inert cuvettes with no glues or epoxies, and with exacting dimensional and optical tolerances.  

Materials
The materials used in cells are designated by the letter in the catalogue number, Useful ranges are listed below and shown in the transmission spectra below.

Q  Spectrosil® Quartz     190 through 2700 nm   Spectrosil is recommended for fluorescence
I  Infrasil® I     220 through 3800 nm
G  Optical Glass    334 through 2500 nm
SOG  Special Optical Glass    320 through 2500 nm
PX Borosilicate     325 through 2500 nm

Material Code: G	Standard Glass	Material: B270, optical crown glass
Specification	Value	Units
Refractive Index	1.5251	ne at 546nm
	1.5230	nd at 588nm
Density	2.55	g/cm3
Modulus of elasticity	E=71.5	103 N/mm2
Coefficient of Thermal Expansion	95 x 10-7/K	temperature range = 20-300oC
Useable optical range	334 to 2500	nanometers

Material Code: SOG	Special Optical Glass	Material: K5
Specification	Value	Units
Refractive Index	1.52458	ne at 546nm
	1.52249	nd at 588nm
Density	2.59	g/cm3
Modulus of elasticity	E=71.0	103 N/mm2
Coefficient of Thermal Expansion	96 x 10-7/K	temperature range = 20-300oC
Useable optical range	320 to 2500	nanometers

Material Code: PX	Pyrex®	Material: Borosilicate
Specification	Value	Units
Refractive Index	1.473	nd at 587.6nm
Density	2.23	g/cm3
Modulus of elasticity	E=64	103 N/mm2
Coefficient of Thermal Expansion	33 x 10-7/K	temperature range = 20-300oC
Useable optical range	320 to 2500	nanometers

Material Code: Q	Spectrosil®	Material: Far UV Quartz
Specification	Value	Units
Refractive Index	1.551	200nm
	1.506	254nm
	1.488	300nm
	1.470	400nm
	1.458	600nm
	1.450	1000nm
Density	2.2	g/cm3
Modulus of elasticity	73x106	Kpa
Coefficient of Thermal Expansion	5.3 x 10-7/K	temperature range = 0-1000oC
Useable optical range	170 to 2700	nanometers

Cell specifications:
Starna spectrophotometer cells and other quartz and glass assemblies, unless precluded by design, are assembled using a fully fused method of construction. This technique, ensures that cells are fused into a single homogeneous entity using heat alone, without intermediate bonding materials. All cells are then carefully annealed to remove any residual strain from the fusing process. This ensures maximum physical strength as well as resistance to solvents.
 
Pressure: With few exceptions, most cells can be used safely with pressure differentials of up to 3 x 105Pa (3 Bar) and some up to10x105Pa (10 Bar).

General specifications:
Windows parallel to: better than 3 minutes of arc
Window flatness to: better than 4 Newton fringes
Window polish, standard: 60/40 scratch/dig
Window polish, laser: 20/10 scratch/dig

Material Path lengths Tolerance:
Glass less than 10mm ± 0.02mm
Glass 10 to 30mm ± 0.1mm
Glass 40 to 100mm ± 0.2mm
Special Optical Glass up to 20mm ± 0.01mm
Special Optical Glass 30 to 100mm ± 0.02mm
Quartz 0.01 to 0.05mm ± 0.002mm
Quartz 0.1 to 0.4mm ± 0.005mm
Quartz 0.5 to 30mm ± 0.01mm
Quartz 40 to 100mm ± 0.02mm

Flow cells with path lengths of less than 0.5mm are measured by an interference method both before and after final fusing. Calculation on this measurement provides an uncertainty of path length better than 0.2 microns (0.0002mm). Path length certification can be supplied for individual cells for a small additional charge.

Standard window thickness is 1.25mm, polished to better than 4 Newton Fringes per centimetre in the viewing area, typically flat to better than 1 micron (0.001mm) over the window area.

Chemical Compatibility: Although cells can be used with most solvents and acidic solutions, fluorinated acids such as Hydrofluoric Acid (HF) in all concentrations should be avoided as they will attack the quartz itself. Strong basic solutions (pH 9.0 and above) will also degrade the surface of the windows and shorten the useful life of the cells.
    
"Z" dimension or beam height. - IMPORTANT!
The 'Z' height of a spectrophotometer is the distance from the bottom of the cell holder cavity to the center of the incident light beam
profile, which can be round, rectangular or curved. For the most efficient use of energy and sample volume the sample chamber aperture should ideally
encompass the light beam with a small extra margin to avoid beam clipping.

Manufacturers have generally designed their instruments with ‘Z’ dimensions ranging from 5 to 20mm with 8.5 or 15mm being the most popular. If you don't know the beam height in your instrument, cut a piece of paper to fit in the cell holder, marked off at 8.5, 15 and 20mm. Illuminate the paper with the spectrometer to see where it falls.

Many cuvettes will work with any beam height, but others are designed with small apertures (such as micro and sub-micro volume cells) and you must order the cell with a specified "z" dimension.

Cuvette 'Z' Dimension per Instrument
Manufacturer: 'Z' Dimension:
Agilent® 15 mm
Beckman® 8.5 mm
Bio-Rad® 8.5 mm
Eppendorf® 8.5 mm
GBC® 15 mm
Hewlett Packard® 15 mm
Hitachi® varies by instrument
Jasco® 11 mm
Ocean Optics® 15 mm
Perkin-Elmer® 15 mm
Pharmacia® 15 mm
Shimadzu® 15 mm
StellarNet® 15 mm
Thermo Spectronic® 8.5 and 15 mm
Turner® 8.5 mm
Varian® 20 mm
Spectrecology  15mm
Wasatch Photonics  15mm