Grind the test sample to the consistency of fine flour. Weigh out approximately 10 mg of the sample and thoroughly mix it with 200 mg of potassium bromide powder. You can use slightly more or less sample as long as the concentration of your sample in the final mixture is between 1 percent and 5 percent by weight.
Fill the sample diffuse reflectance cup with the sample/potassium bromide mixture you prepared. The mixture in the cup should be at least 1.5 mm deep and loosely packed. Fill the background cup with pure potassium bromide.
Place both sample and background cups in the diffuse reflectance accessory and power up the spectrophotometer. Scan the background cup to acquire a background spectrum and then scan the sample cup to obtain a raw sample spectrum. The spectrophotometer software will automatically subtract the background spectrum from the sample spectrum to remove any effects of the potassium bromide.
Open the spectra conversion software utility and choose from the menu the option to perform a Kubelka-Munk conversion on the raw sample spectrum. This conversion will compensate for diffuse reflectance effects. Compare the resulting processed sample spectrum to standard spectra from reference sources to determine the identity and composition of the sample.