Optilab Refractive Index Detector for HPLC/GPC

The Optilab® differential refractive index (dRI) detector may be used in conjunction with any HPLC, FPLC, GPC or FFF separation system, plus a Wyatt DAWN® or miniDAWN® multi-angle light scattering (MALS) detector, for the absolute determination of the molar mass of all types of macromolecules in solution. While its sensitivity matches the very best HPLC RI detectors, its dynamic range exceeds that of any comparable instrument by 10-100x, with no range settings - meaning you can characterize very large and very small peaks, simultaneously. 

In addition to dRI, the Optilab also measures the absolute refractive index (aRI) of a solution, important for characterizing solvents. The high-concentration (HC) model provides an extended measurement range suitable for high-concentration samples (up to 180 mg/mL of protein) or gradient-elution chromatography such as ion-exchange.


  • dRI noise: 7.5x10-10 RIU (HC model: 1.5x10-9 RIU)
  • dRI range: ±4.7x10-3 RIU (HC model: -2.6x10-3 to +34x10-3 RIU)
  • Dynamic range: 12,000,000:1 (HC model: 23,000,000:1)
  • Absolute RI sensitivity: ±0.002 RIU
  • Absolute RI range: 1.2 – 1.8 RIU
  • Temperature control: heated/cooled 4 - 65°C, including active stabilization—even at room temperature 
  • Wavelength: 660 nm, matched to MALS instruments; other wavelengths available 
  • Touch-panel display for immediate access to data, diagnostics and settings


  • Universal online concentration measurement for chromatography, especially SEC-MALS and FFF-MALS.
  • Analysis of conjugated proteins, co-polymers and nanoparticle-encapsulated drugs/proteins/DNA/RNA when combined with a MALS and UV detector 
  • Offline measurement of second virial coefficient A2 (B22)
  • Offline measurement of the specific refractive index increment dn/dc, at the same wavelength as the MALS laser (critical for accurate macromolecular characterization)
  • Ion-exchange chromatography with MALS (IEX-MALS) – measure dRI over the entire salt gradient
  • Composition-gradient MALS (CG-MALS) – measure protein-protein interactions at high concentration

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