Ion chromatography (IC) is the prevalent technique for the analysis of inorganic anions. Although dedicated hardware is available to separate and detect the analytes, modular IC systems are characterized by significant extra-column dispersion, which reduces the separation efficiency. This additional band broadening can be eliminated by the integration of multiple system components onto a chip platform. Such a miniaturized device would potentially enable high-efficiency separations for the analysis of minute amounts of sample with reduced solvent consumption, which is important in, e.g., clinical diagnostics and life-science research. Such compact systems could also be used for environmental field analysis and for at-line quality control in industry.
The current contribution describes the development of a miniaturized device integrating key components of an IC system – separation, suppression, and detection – on a single modular microfluidic platform. Practical aspects of microfabrication using micromilling, bonding, and micro-to-macro interfacing to create thermoplastic chips for high-pressure LC applications are discussed. Optimization of the production process has resulted in chips presenting burst pressures up to 48 MPa. The implementation of a monolithic stationary phase via UV-polymerization and high-pressure slurry packing in chips is demonstrated. Different strategies to functionalize the supporting matrix are discussed. To expand the functionality of the module, the possibility of integration of on-chip injections is explored.
To enable conductivity detection, the separation chip is complemented with a microfluidic membrane suppressor. A stacking approach enables eluent transfer from the separation chip with minimal extra-column band broadening and peak dispersion. The 1.2 µL chemically-regenerated suppressor has a dynamic capacity of 0.35 µEq/min, enabling the conversion of hydroxide eluents up to 75 mM under optimized operating conditions, making the device compatible with typical gradient conditions applied in capillary-scale separations. Dispersion characteristics were experimentally determined and optimized to maintain separation efficiency. Integration of electrodes on the microfluidic membrane suppressor to establish on-chip conductivity detection yielded detection limits in the sub-ppb level for common anions. The developed hardware was utilized to analyze minute amounts of sample taken from an ice core drilled in Antarctica, allowing to detect evidence of volcanic and biological activity.
Original languageEnglish
StatePublished - 19 Jun 2017
Event45th International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC 2017) - Prague, Czech Republic

Conference

Conference45th International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC 2017)
Abbreviated titleHPLC-45
CountryCzech Republic
CityPrague
Period19/06/1722/06/17

ID: 32510591