Refractive-index detection is commonly used in chemical and biochemical analysis to perform universal solute detection as well as temperature measurements in nanoliter volumes. Several approaches have been used to measure the change in refractive index in small volumes, but the probe volume is extremely large for nanoliter applications. In response to this challenge, researchers at Texas Tech University in Lubbock have developed a universal refractive-index detector based on backscatter interferometry.

Called the micro-interferometric backscatter detector, the system features a scalable train and can probe ultrasmall volumes. This "optical train" has been used for picoliter millidegree thermometry, nanoscale polarimetry, capillary electrophoresis, flow sensing and more. The researchers now are moving toward label-free protein-binding assays. They described the method in the Oct. 15 issue of Analytical Chemistry.