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
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