Waters/Wyatt microOptilab On-line Differential Refractometer

Independent of Chromaphores

Independent of chromaphores or fluorophores, differential Refractive Index (dRI) detectors measure concentrations of all types of samples in almost all solvents. The microOptilab brings the universal detection capabilities, unsurpassed concentration range, and superb sensitivity and linearity – familiar from the Optilab™ – to the domain of UHPLC.

SEC-MALS with UHPLC

Like standard SEC, UHPLC-SEC analysis relying on column calibration with molecular standards is unreliable when the standards do not accurately reflect your samples in terms of conformation, non-ideal (e.g., hydrophobic) column interactions or reversible association. SEC-MALS employs a microDAWN™ MALS detector downstream of the SEC column and UV detector, to determine molar mass / molecular weight distributions of macromolecules independently of column calibration.

Refractive index detection is an important component of any SEC-MALS system, and necessary for analyzing conjugated proteins or polymers devoid of chromaphores. The microOptilab connects with the microDAWN MALS detector for a complete UHP-SEC-MALS setup that transfers the many benefits of SEC-MALS analysis to the realm of UHPLC.

Key benefits

• Very low band broadening, < 4 µL, to maintain the resolution of very narrow UHPLC peaks
• Extraordinary dRI measurement range, -4.7 x 10 -3  to +4.7 x 10 -3  RIU (comparable to 25 mg/mL protein in PBS)
• Highly sensitive, ± 1.5 x 10 -9  RIU across the entire measurement range
• Measures solvent refractive index, require for MALS calculations
• Measures at the same wavelength as the MALS detector, for maximum accuracy in MALS calculations
• Temperature range 4 °C to 65 °C for proteins and polymers that require a range of temperatures
• High-resolution, touch-screen front panel displays data graphs and instrument diagnostics, even with the host computer turned off

Unparalleled features

• Considering the extremely small peak volumes of UHPLC, band broadening in the microOptilab is kept to the absolute minimum, at less than 4 µL, as compared to 20 - 40 µL or more for standard RI detectors. As a result, the superior resolution from UHPLC columns and instruments will not be compromised with the microOptilab RI detector.
• Even though the microOptilab offers a dRI measurement range orders of magnitude beyond that of other UHPLC dRI detectors, unlike other detectors there are no range or gain settings in the microOptilab. The full range of instrument detection is always present, and the full sensitivity exists over the entire range. The small flow cell and proprietary temperature regulation enable stable RI baselines and signals which further enhance the detector's sensitivity.
• Unlike all other dRI detectors, the microOptilab also measures absolute refractive index in order to determine solvent RI, necessary in light scattering calculations and useful in assessing the accuracy of mixing of solvent gradients.
• The microOptilab can be operated below ambient temperatures as easily as above ambient. No hassle temperature control can be programmed down to 4 °C or as high as 65 °C.
• The microOptilab is compatible with all UHPLC systems.

Specifications

Measurement Capabilities – Differential Refractive Index

• Differential RI Measurement Range:
  –0.0047 to +0.0047 RIU
• Peak-to-Peak Noise:
  ±1.5 × 10⁻⁹ RIU
  (Measured per ASTM-E1303-95 at 25 °C with a 0.5 sec collection interval)
• Response Time:
  User-selectable from 0.04 to 5 seconds
• Absolute Refractive Index Range:
  1.2 to 1.8 RIU
• Absolute RI Sensitivity:
  ±0.002 RIU

Fluidics and Flow Properties

• Band Broadening:
  <4 µL (at 0.3 mL/min)
• Fill Volume (Inlet Tubing + Flow Cell):
  13.7 µL
• Outlet Tubing Volume (0.030” ID):
  228 µL

Pressure Ratings

• Inlet Back Pressure (0.5 mL/min H₂O @ 20 °C):
  <320 psi (22 bar)
• Maximum Permissible Outlet Pressure:
  30 psi (2 bar)

Temperature Control

• Control Range:
  4 °C to 65 °C
• Stability:
  ±0.005 °C for precise thermal regulation

Optical Source and Safety

• Light Source:
  660 nm wavelength
• Safety Sensors:
  Integrated vapor and liquid leak detection

Electronics and Connectivity

• Digital Output Rate:
  25 Hz
• Analog Output:
  ±10 V or ±1 V, 18-bit resolution
• Computer Interface:
  Ethernet for seamless data connectivity

Auxiliary I/O Ports

• Inputs:
  • Analog In (16-bit, ±10 V A/D)
  • Zero dRI
  • Purge
  • Recycle In
  • Autoinject In
  • Alarm In
• Outputs:
  • Autoinject Retransmit
  • Alarm Out
  • Recycle Out (Orbit™ valve switching)

User Interface

• Display:
  7” (178 mm) high-resolution multi-touch screen for viewing live signals, diagnostics, and configuring instrument settings

Instrument Dimensions

• Size: 58 cm (L) × 36 cm (W) × 18 cm (H)

Other Refractive Index Detectors

• Optilab™ - A unique on-line differential refractometer for measuring concentration of any macromolecule, regardless of chromophores. Temperature controlled from 4 °C to 65 °C. The high-concentration option accommodates protein concentration up to 180 mg/mL.