Thermal Expansion Pump for Capillary High-Performance Liquid Chromatography

摘要

A thermal expansion pump (TEP) based on a principle ofnliquid thermal expansion for capillary high-performancenliquid chromatography has been developed. The novelnpump is capable of generating a continuous flow at highnpressure for constant and stable delivery of binary solventsnfrom nanoliters to microliters per minute withoutnsplitting. Theoretical equations for controlling fluidicnoutput of this pump have been established and validatednby a series of experiments. Factors affecting flow rate,nsuch as density discrepancy, liquid compressibility, andnmass loss in output, were taken into account. An assemblynof the pump system employing two groups of thermalnexpansion pumps (TEPs) working in turns were fabricated,nand a controlling strategy for the pump system tonmaintain a continuous delivery without pressure fluctuationneven at switching points was also developed. Bothnisocratic and gradients of binary solvent delivery by thenTEPs were performed. Reproducibility and standardndeviation at different flow rates were determined. Ancapillary high-performance liquid chromatography (μ-nHPLC) system consisting of the TEPs, an injection valve,na homemade packed capillary column (20 cm × 100 μmni.d. with 5 μm C18), and a laser-induced fluorescencendetector was set up, and sample separations were carriednout. Results of RSD ) 4% for flow and RSD ) 2% fornretention times at 500 nL/min were achieved. Such anpump system has almost no moving parts except for thensolvent switches. Its overall costs of manufacture andnrunning are very low. It is proven that the TEPs systemnhas great potential and competitive capabilities in capillarynliquid chromatography.