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
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
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
Mark-Howink Coeff's Determination
Instruments Comparison
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