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 GPC/SEC Application.

Why Viscometry in GPC/SEC

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, column calibration is required

Pure GPC/SEC Separation is required

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

Typically, complex combination with other detectors

Results obtained by GPC/SEC 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