Introduction Generally, a sample for CD measurement needs to be in a liquid state to allow transmission measurement, more recently there has been increasing requirement for CD measurement of samples that are insoluble or may change structure in solution. These types of sample are best measured in solid state. Although CD measurement can be made in transmission for solid samples, there is a requirement for sample preparation; such as making a pellet and if sample dilution is required, sample recovery can be difficult. As an alternative, measurement using Diffuse Reflection (DR) CD is recommended. 1), 2) This application note illustrates the use of DRCD measurement with the DRCD-575 diffuse reflectance accessory (See Fig. 1.) optimized for the J-1500 CD spectrometer with the multi-probe simultaneous CD/LD measurement. DRCD uses incident light to illuminate a solid sample and JASCO圓二色光譜儀CD J-1500