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Restriction capillaries as an innovative mixing unit for intermediate mobile phase exchange in multidimensional
Glenn Loos1, Konstantin Shoykhet2, Monika Dittmann2
1KU Leuven - University of Leuven, Department for Pharmaceutical and Pharmacological Sciences, Pharmaceutical Analysis, Herestraat 49 bus 923, B-3000 Leuven, Belgium.
Journal of Chromatography. A
|April 5, 2017
Summary
A new mixing unit enables simultaneous analysis of polar and non-polar compounds using orthogonal columns. This innovative approach improves compound separation efficiency in a single analytical run.
Area of Science:
- Analytical Chemistry
- Chromatography
Background:
- Orthogonal column coupling is essential for comprehensive compound analysis.
- Mobile phase incompatibility between orthogonal columns hinders serial coupling.
- A robust mixing unit is needed to bridge mobile phase differences.
Purpose of the Study:
- To develop and validate a novel mixing unit for serial coupling of orthogonal columns.
- To enable simultaneous analysis of both polar and non-polar compounds in a single run.
- To optimize mobile phase dilution for enhanced separation performance.
Main Methods:
- Utilized two restriction capillaries with varying flow resistances for mobile phase dilution.
- Implemented the mixing unit within an ultra-high performance liquid chromatography (UHPLC) system.
- Employed three high-pressure switching valves and two T-pieces for system integration.
- Validated dilution ratios using the Hagen-Poiseuille law and investigated dilution volumes for optimal recovery.
Main Results:
- Demonstrated predictable and adjustable mobile phase dilution ratios by modifying capillary dimensions.
- Achieved high compound recoveries (82-99%) under optimized dilution conditions.
- Showcased excellent repeatability for the developed analytical method.
- Successfully applied the system to separate 20 pharmaceuticals with a wide range of lipophilicity (log D: -5.75 to 4.22).
Conclusions:
- The proposed mixing unit effectively addresses mobile phase incompatibility in serial orthogonal column chromatography.
- The system allows for sensitive and repeatable analysis of diverse compounds in a single run.
- This technology offers a valuable tool for pharmaceutical analysis and other complex mixture separations.