Wyatt Technology


Optilab refractometer


Universal Detection for UHPLC and SEC-MALS

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.

  Download our Application Note on the microOptilab


    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.

  • Revolutionary dRI detection optics

    The microOptilab inherited the breakthrough optical design of the award-winning Optilab dRI detector which makes use of a 512-element photodiode array and proprietary algorithms, instead of the usual bi-cell design, bringing RI detection into the 21st century. The microOptilab added improvements in optical stability, temperature control, LED light source intensity, and increased on-board computing power; and of course reduced fluidics volume and band broadening in order to achieve compatibility with UHPLC.

    Minimal loss of resolution

    Each detector downstream of SEC adds band broadening and dispersion, according to its internal fluidic volume and flow path. With a total internal volume of < 14 µL up to and including the flow cell, and consequentially band broadening < 4 µL, the microOptilab can be used with confidence to detect and analyze narrow UHPLC peaks.

  • RI Calibration Kit - Pre-made RI calibration standards are available to speed up RI calibration. Can be used to calibrate any Optilab or third-party differential RI instrument.

    WISH Injection Module - The Wyatt Injection System High-Pressure (WISH) is ideal for use with an Optilab RI detector for the determination of dn/dc in "batch" mode.

    Microbatch Kit - Used to inject samples into the flow cell of a MALS detector, and in determining dn/dc.

  • Differential Refractive Index  
       Dynamic Range -0.0047 to +0.0047 RIU
       Peak-to-peak noise * ± 1.5 x 10-9 RIU (across entire range)
       Digital Output 22+ bits @ 25 Hz
       Analog Output ± 10 V or ± 1 V output, 18 bits resolution
    Response Time 0.04 to 5 seconds, user selectable
    Absolute Refractive Index  
       Range  1.28 to 1.8 RIU
       Sensitivity  ± 0.002 RIU
       Band Broadening ** < 4 µL
       Flow Cell Volume 7.4 µL
       Inlet Tubing (0.005" ID) 6.5 µL
       Outlet Tubing (0.030" ID) 275 µL
       Back pressure created at inlet port <160 psi (11 bar) @ 0.5 mL/min of pure water, 20°C
       Maximum permissible back pressure at outlet port 30 psi (2 bar)
       Wetted Materials 316 stainless steel, PTFE, fused silica
    Sample Temperature  
       Control Range  4°C to 65°C
       Regulation ± 0.005°C
    Light Source 660 nm standard; Other wavelengths available
    Safety Sensors Vapor and liquid (leak)
    On Board Computer  
       CPU 2 GHz VIA C7 Processor
       Display/User Interface 6.4", 16-bit, color high resolution LCD display
       Digital Communication Ethernet
    Auxiliary I/O  
       Inputs Analog In (16 bits, ±10 V A/D), Zero dRI, Purge, Recycle In, Autoinject, Alarm In
       Outputs Analog Out (18 bit dRI data), Autoinject Retransmit, Alarm Out, Recycle Out (to switch Orbit between waste and recycle)
    Dimensions 60 cm (L) x 36 cm (W) x 17 cm (H)
    Weight 11.5 kg (25.4 lbs)
    Power Requirements Universal input, AC 100/115/220/240 V, 50/60 Hz
    Power 480 W max, 86 W typical

    * Short term peak-to-peak noise is measured as per ASTM-E1303-95(2000) using a 0.5 sec collection interval (1-sec time constant) and temperature set to 25°C.

    ** Peak broadening measured over full width at half max, flow rate = 0.3 mL/min.

    Host PC requirements may be found in Computer Requirements.

    Specifications subject to change without notice.


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Wyatt Technology is the recognized leader in light scattering instrumentation and software for determining the absolute molar mass, size, charge and interactions of macromolecules and nanoparticles in solution.

Wyatt's line of multi-angle static light scattering products couple to size exclusion chromatography (SEC-MALS), field-flow fractionation (FFF-MALS), and stop-flow composition-gradient systems (CG-MALS). Our dynamic light scattering (DLS) products operate in traditional cuvette as well as on-line and automated, high-throughput modes. We also offer unique instruments for electrophoretic light scattering (MP-PALS), differential refractometry, and differential viscosity.

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