Purpose
Starna Green is an excellent general-purpose reference for the routine qualification of ultraviolet and visible spectrophotometers in the wavelength range 250 nm – 650 nm. It was specially developed for use with instruments having wider bandwidths (up to 20 nm) but is a useful reference for all instruments. Three peaks are available for wavelength qualification (258, 416 and 630 nm) and the reference can be used at absorbances up to 5 A. Starna Green is very stable, non-toxic and REACH compliant.
This reference is also available specially packaged for the qualification of dedicated microvolume and drop technology instrumentation.
Description and Discussion
Most reference materials available for instrument wavelength qualification are chosen for their well-defined spectra, with sharp absorption bands, and are usually recommended for instruments with spectral bandwidths of 3 nm or less. This is partly because most absorption bands are asymmetric, so the apparent peak wavelength will change with bandwidth and partly because wider bandwidth instruments may be unable to resolve some peaks at all.
The use of aqueous dye solutions, however, is an established and well-recognised method for the validation of the absorbance scale and linearity of a spectrophotometer. Starna Green is a specially formulated dye solution with three broad but well-defined peaks that can be certified for both wavelength and absorbance value in the UV and visible regions, at bandwidths up to 20nm.
Typical spectra
The reference is available in a range of ten concentrations, covering nominal absorbance values from 0.25A to 5A
Typical values obtained at the certified wavelengths are:
| Nominal Concentration | Nominal Certified Wavelength and Absorbance Values | ||
| 258 nm | 416 nm | 630 nm | |
| 25 | 0.259 | 0.253 | 0.254 |
| 50 | 0.514 | 0.505 | 0.509 |
| 75 | 0.757 | 0.754 | 0.759 |
| 100 | 1.007 | 1.01 | 1.017 |
| 150 | 1.492 | 1.485 | 1.476 |
| 200 | 1.99 | 1.979 | 1.968 |
| 250 | 2.487 | 2.474 | 2.46 |
| 300 | 2.984 | 2.969 | 2.952 |
| 400 | 3.979 | 3.959 | 3.936 |
| 500 | 4.974 | 4.949 | 4.92 |
Note: The above values are for guidance only. The Calibration Certificate accompanying the references gives actual values, and only these certified values should be used for instrument qualification. Starna Green References are calibrated at 1 nm and 5 nm bandwidths. Other bandwidths on request.
Catalogue Number
Available as a convenient set of four references and blank cell:
| Catalogue Number | |
| Starna Green Linearity Set 25,50,75 & 100 concentrations & blank | RM-25G50G75G100G |
References are also available individually. Any combination of references can be ordered as a set by combining the catalogue numbers as in the example above. A hydrochloric acid blank cell is supplied with each reference or set of references.
| Nominal Concentration | Nominal Certified Wavelength and Absorbance Values | CATALOGUE NUMBER | ||
| 258 nm | 416 nm | 630 nm | ||
| 25 | 0.259 | 0.253 | 0.254 | RM-25G |
| 50 | 0.514 | 0.505 | 0.509 | RM-50G |
| 75 | 0.757 | 0.754 | 0.759 | RM-75G |
| 100 | 1.007 | 1.01 | 1.017 | RM-100G |
| 150 | 1.492 | 1.485 | 1.476 | RM-150G |
| 200 | 1.99 | 1.979 | 1.968 | RM-200G |
| 250 | 2.487 | 2.474 | 2.46 | RM-250G |
| 300 | 2.984 | 2.969 | 2.952 | RM-300G |
| 400 | 3.979 | 3.959 | 3.936 | RM-400G |
| 500 | 4.974 | 4.949 | 4.92 | RM-500G |