The procedure for using the stray light references is similar for all materials. Set your spectrophotometer’s wavelength 20 nm above the cutoff for the stray light reference that you are using (for Potassium Iodide you would start at 280 nm). 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, a service technician may be required 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.