Chromatography

Biography

Biography: Shaorong Liu

Abstract

Abstract. In this work, we demonstrate narrow open tubular liquid chromatography (NOTLC) for ultra-high efficiency and ultra-fast separations. Theoretical studies has predicted that open-tubular columns would offer the best means of achieving high separation efficiencies for liquid chromatography and that the optimal i.d. of the open tubular column would be in the range of 1 to 2 um. However, NOTLC has never been systematically tested using columns in this i.d. regime due to the intrinsic challenges of utilizing such narrow columns, and high-efficiency NOTLC has remained only an idea for decades. Here we use 2-um-i.d. capillaries and obtain ultra-high efficiency and ultra-fast results for amino acid and peptide separations.

The narrow open tubular (NOT) column was coated with trimethoxy(octadecyl)silane (C18). An Agilent 1200 HPLC pump coupled with a flow splitter served as a gradient pump. A 6-port valve was used for sample injection. A laser-induced fluorescence (LIF) detector was employed to monitor the separation process. Fig. 1A presents the results for amino acid separation; an expanded view is shown in the inset for clear presentation. Many of the peaks have full widths at half maxima (FWHM) of 0.3-0.5 s. Because of the use of a highly mass-permissive open-tubular column, the elution pressure was low (600 psi) and the separation was complete with 6 min. Fig. 1B presents a chromatogram for separating trypsin-digested cytochrome C and we estimated a peak capacity of 810 within 54 min. Fig. 2C presents a separation of pepsin/trypsin digested E. coli lysate, and we estimated a peak capacity of 1870 within 174 min. Fig. 2D presents six fast NOTLC separations. Under an elution pressure of ~3000 psi, the separation was complete within ~1.3 s (see chromatogram I) and all six amino acids were resolved within 300 ms. The above efficiency, peak capacity, and separation speed are all extraordinary or record numbers