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Features at a glance

  • Fast instrument warm-up, ~ 1 hour!
  • Sensitivity, 2.5 x 109 ΔRIU
  • Autozero
  • Reference cell flush
  • 9 measurement ranges
  • DNDCW Windows™ software
  • Active temperature control to 80 °C
  • Wavelength selection: 620, 535 or 470 nm

Brookhaven's BI-DNDC Differential Refractometer

Product Description

The BI-DNDC is a deflection type refractometer that may be purchased for use in either batch or GPC/SEC mode. In batch mode, the specific refractive index increment, dn/dc, is determined. This value is required as a parameter in molecular weight measurements using light scattering. In GPC/SEC mode, dn/dc is already known, and the instrument is used as a concentration detector for GPC/SEC applications.


All major features are user programmable in order to achieve the maximum flexibility. The BI-DNDC can be set using the front panel controls and read using the LED readout or by an external computer. It includes a microprocessor, which allows user-friendly handling of all functions of the instrument, as well as refractive index and temperature data transfer to a personal computer via a standard serial interface.

Most importantly, warm-up time for the BI-DNDC is only one hour, much less than other models on the market.

Determination of dn/dc

The dn/dc determination requires calibration of the batch mode instrument with a solvent/solute combination with known dn/dc, typically KCl in water. The calculated constant is not solvent dependent and may be used for all further measurements. In batch mode, the instrument comes with BI-DNDCW software for use with an external PC. Included with the BI-DNDC instrument is a syringe kit with PEEK™ and Teflon ® tubing, fittings and syringes.

Sample may be recovered and reconstituted, if required. Typically, five or more concentrations, ranging from 0.1 to 10 mg/mL, are recommended. New instrument readings can be performed in a matter of minutes since it only takes ~ 0.5 mL of liquid to flush out the previous sample.

Determination of concentration

In this mode, the BI-DNDC serves as a highly sensitive concentration detector. Even better, with the right wavelength and the BI-MwA, the BI-DNDC becomes part of a system that eliminates GPC/SEC column calibration.

Cell Angle45°
Cell Volume (Batch Mode)8 µL
Dead Volume (Inlet to Cell/Cell to Outlet)GPC Mode Sample Cell: 0.25 µL, GPC Mode Reference Cell: 100 µL
Batch Mode Sample Cell100 µL: Batch Mode Reference Cell: 8 µL
Measurement Ranges (ΔRIU Full Scale)(GPC mode)6x10-4, 3x10-4, 1.5x10-4, 7.5x10-5, 3.75x10-5, 1.87x10-5, 9.3x10-6, 4.6x10-6, 2.3x10-6
no Range1.0 to 1.75 RIU
Sensitivity (GPC Mode)1.5 ng (Fructose in H2O)
Noise Level< 2.5 x 109, ΔRIU, 25 °C
Temperature Accuracy± 0.5 °C
Temperature Stability± 0.01 °C
Temperature RangeAmbient to 80 °C
Specify Wavelength620 nm, 535 nm or 470 nm, factory set
Tubing I.D.: GPC Mode Sample Cell0.25 mm, GPC Mode reference cell: 0.5 mm; Batch Mode sample cell: 0.5 mm
Batch Mode Reference Cell0.5 mm
Flow Rate (typical/maximum)1.0/3.0 mL/min (Analytical Mode), 5.0/12.0 mL/min (Preparation Mode)
Time Constant0.1 to 2 seconds
Analog Signal Output1 and 10 volt bipolar, full scale
Digital Signal OutputRS-232/COM port
SoftwareBI-DNDCW for Batch Mode measurements
Data Transfer Rate (baud)4800, 9600, 19200, 38400, 57600, 115200 Digital Inputs: Flush, Zero, Sync, Error
Weight8 kg
Size160 x 175 x 340, mm
CertificationsCE Marked

A policy of continual improvement may lead to speficiation changes