Dual-Detector Technology in modern GPC

K-D. Bures,

This short paper illustrates the advantages of the combined RI / Viscometer Dual-detector compared with conventional, separate Refractometer - Viscometer set-up in SEC Application.

Why Viscometry in GPC

Large dynamic range in terms of molar mass from few hundreds to tens
of million g/mol
Large quantity of information (within the whole MW range)

Only "good" alternative when SLS fails (co-polymers)

Cross-validation of results by correlation with other MWD techniques like SLS

Drawbacks of Viscometry

When used for MW Distribution, GPC calibration is required

Pure GPC Separation is required

High requirements to the GPC System
(Pump pulsation, flow stability, columns resolution)

Typically, complex combination with other detectors

Results obtained by GPC Viscometry

Intrinsic Viscosity [ETA]) and [ETA] Distribution
(Absolute, primary information)

Molecular Weight Distribution and its Moments (Mn, Mw, Mz)
(with use of Universal Calibration)

Mark-Howink Coefficients
(when sample has a sufficiently broad polydispersity, Mw/Mn > 1.8)

Sphere-equivalent Hydrodynamic volume and Radius

Branching parameters (g')

"Common" combination with a RI Detector

Serial Combination

Drawbacks of the "Common" Combination

Flow split needs accurate adjustment)

Reduced sensitivity due to flow split)

Flow Split requires check on a regular time-base

Increases Band-Broadening

Makes combination with further detectors complicated)

RI / Viscometer Detector Design

Dual Detector Design

Advantages of the WGE Dual-Detector Technology

Simultaneous, In-Situ Detection of ETA and Concentration

No or low Band-Broadening

Matched Detection Volumes for the two Detectors

Higher Sensitivity compared to the "Common" Combination

Troubles-free Combination with other Detectors (i.e. SLS)

RI-Viscometer Dual-Detector Signals

Dual-Detector Signals

Mark-Howink Coeff's Determination

Mark-Howink Plot

Instruments Comparison

Dual-Detector Signals

Final Words on the RI / Viscometer Dual-Detector

The WGE Dual-Detector is the ONLY true RI/Viscometer Available

The WGE Dual-Detector offers the highest achievable sensitivity

The WGE Dual-Detector is easily connected to existing GPC Systems

The WGE Dual-Detector can be easily combined with a SLS Detector