Diode-laser-based optical rotation detector for high-performance liquid chromatography and on-line polarimetric analysis

A simple polarimeter with microdegree sensitivity based on a near-infrared (820 nm) semiconductor diode laser is described, and signal to noise ratio analysis is discussed. With the use of small-volume flow cells (typically 8 {mu}L) its utility as a high-performance liquid chromatography (HPLC) detector in the gradient elution separation of carbohydrates is shown. Coupled with a UV detector, the HPLC enantiomeric purity determination of D-/L-tryptophan mixtures without chiral separation is demonstrated. On a laboratory-scale system an application from the sugar industry is reported, monitoring molasses flow streams which are opaque at visible wave-lengths.