LIQUID CHROMATOGRAPHY WITH A REFRAECTOMETRIC DETECTOR
A refractometric detector or a refractive index (RI or RID) detector measures the refractive index of an analyte with respect to the solvent. It is a universal detector but has low sensitivity. Often used as detectors used in GPC (size exclusion chromatography).
The refractometer contains a flow cell with two parts: one for the sample and the other for the reference solvent. The detector measures the refractive index of both components. As soon as the solvent flows through a sample component, the measured refractive index of both components is the same, but as the analyte passes through the flow cell, the two measured refractive indices are different. The difference appears as a peak in the chromatogram. The detector is not suitable for applications where gradient analysis is necessary. Usually, these types of detectors are characterized by low sensitivity, but Wyatt has launched the Optilab series.
In our laboratory, RI detectors are used mainly for the analysis of polymers and volatile substances, which cannot be analyzed using ELSD or MSxMS.