Diffuse reflectance (DR) spectrometry is becoming an important technique for characterizing powdered samples; however, surprisingly little is known about the technique, and its use will be limited until the quantitative behavior is more thoroughly understood.The effect of optical geometry on DR spectra of several types of samples including materials without sharp absorption bands, neat powdered materials (organic materials with weak absorption bands, and inorganic materials with bands of greater absorption), effect of particle size for all samples, and effect of dilution of the samples in KCI will be studied, as will varying the angles of incidence and reflection. The feasibility of measuring the DR spectra of powders dispersed in liquids will also be studied.Such measurements could have considerable significance in the detection of low levels of drugs and their metabolites in physiological fluids. In addition, because a number of manufacturers produce DR spectrometers that show differences that can (and do) affect the spectra, it is important to determine the optimum geometry for DR spectroscopy so that a consistency among commercial instruments can be obtained.National Institute Of General Medical Sciences
