A low pressure on-chip injection strategy for high-performance chip-based chromatography

A microfluidic device for high-performance liquid chromatography is presented. The borosilicate glass chip includes a common cross-channel injector and a column chamber. The column chamber comprises two constrictions (10 μm) to retain the chromatographic particles via the keystone effect. A packing channel was utilized to introduce the particulate material (3-μm). This channel has been sealed permanently via laser-assisted photopolymerization avoiding dead volumes within the chromatographic pathway. A sampling strategy is presented enabling the directed definition of the sample plug on-chip. The injection process is studied via video microscopy and chromatographic separations of test solutes with fluorescence detection. Our approach, based on on-chip flow splitting, allows the usage of traditional, economic and robust HPLC instrumentation avoiding the need for sophisticated nano-flow equipment. The performance of the chip device and the injection process was demonstrated by reversed-phase chromatographic separations of a mixture of polycyclic aromatic hydrocarbons achieving constant high efficiencies for the chromatographic signals over the whole elution window.