Highly uniform porous silica layer open-tubular capillary columns produced via in-situ biphasic sol-Gel processing for open-tubular capillary electrochromatography

We report a highly uniform porous layer open tubular (PLOT) column for capillary electrochromatography (CEC) analysis. The PLOT column is easily fabricated using a single-step in-situ biphasic reaction, producing homogeneous porous-layer modified surface with ∼240 nm thickness in a 50 μm-id capillary. CEC performance of the PLOT column has been investigated and optimized under various experimental parameters. Using a mixture of naphthalene and biphenyl as the test sample, we show that the PLOT column exhibits good separation efficiency with resolution >3.0 and theoretical plate numbers over 6 × 104, as well as good intra-/inter-day repeatability and column-to-column repeatability. The column has been successfully applied for CEC analysis of three different types of samples without any further modification of the columns, including complicated peptide products from tryptic-digestion of proteins (lysozyme and BSA), β-blockers (basic samples) and polycyclic aromatic hydrocarbons (neutral samples). Efficient separation has been achieved, which could be attributed to the enhanced surface-to-volume ratio of the PLOT column that will increase the interaction between solid phase and mobile phase in CEC. In addition, base-line separation of neutral samples indicates the reversed phase chromatographic property of the PLOT column, which could be induced by the residue of hexadecyltrimethylammonium bromide used in the fabrication process. Our study show that the present PLOT column is a promising approach that can significantly enhance CEC separation efficiency and could be of potential value in analysis of various different samples.