The UV Stray Light Reference, NIST Traceable is made of materials with sharp cutoffs in transmission at specified wavelengths, NIST Traceable with UKAS ISO 17025 accredited certificate of calibration. Detection of stray light in the UV and Visible, with a usable range of 200nm to 390nm, depending on the material. These references are held in a far UV quartz cells that have been permanently sealed by heat fusion
Stray light can be described as an indication by the instrument of transmitted light when in reality there is no light being transmitted through the sample. The presence of more stray light than specified in your instrument operator's manual may cause errors in your analysis. Stray light can be a problem in any wavelength range of the instrument but the problem increases the further into the UV that you will be measuring. The stray light reference materials are useful in determining the amount of stray light in your instrument because each material stops transmitting light below a specified wavelength. Hence, below the specified “cutoff” wavelength, any indication of light transmisson must be stray light. The testing for stray light is important even if the spectrophotometer is not used below 390nm, because it is an excellent indication of the overall system health of the instrument optics, grating and deuterium lamp. Stray light determinations are run against a water blank. This blank is supplied with all NIST traceable stray light references. The Certificate of Traceability supplied with the stray light reference is measured against the water blank supplied with that reference cell. The procedure for using the stray light references is similar for all materials. Set your spectrophotometer’s wavelength 20nm above the cutoff for the stray light reference that you are using (for Potassium Iodide you would start at 280nm). Insert the stray light reference cell in the measurement cell holder and the stray light blank cell in the blank cell holder of your instrument. Scan down into the UV to the lowest wavelength that your instrument manual specifies. Any light transmitted below the cutoff wavelength will be stray light. If the amount of stray light is greater than the specification given in your instrument manual, call a service technician to investigate and correct the problem. Periodically rescan with the same instrument configuration and compare the results. Over time you will have a data trail for your instrument which will make the detection and correction of any problems relating to stray light much more reliable.