thiourea and octadecylsilane

Fritless packed beds comprised of magnetically responsive octadecylsilane bonded silica particles have been constructed for reversed-phase electrochromatography. The magnetic particles were immobilized in the capillary by applying an external magnetic field transverse to the direction of electroosmotic flow. Being subjected to the interplay of fluid dragging and magnetic forces, the initial loosely packed particle assembly was compacted into a uniform packing structure. The magnetically immobilized beds obtained were used as stationary phases for separation of neutral compounds, with retention behavior and column efficiency similar to those of slurry-packed columns. The results suggest that the magnetic attraction approach to fritless column packing may be used for construction of advanced chip-based chromatography, especially in complex architectures comprising curved and intersecting channels.

Topics: Anthracenes; Capillary Electrochromatography; Electromagnetic Fields; Electroosmosis; Equipment Design; Nanoparticles; Silanes; Silicon Dioxide; Thiourea

Nonporous silica spheres (1 microm) were synthesized and bonded with octadecylsilane functionality. These stationary phase particles were packed electrokinetically into fused-silica capillaries with 100 microm id for a length of 20 cm, which was evaluated by using pressurized CEC (pCEC). The efficiency of the C18 RP column was characterized through the theoretical plates of thiourea, benzyl alcohol, toluene, styrene, and naphthalene. The effects of experimental parameters such as the applied voltage, sample size, pump flow rate, pH value and the concentration of the buffer solution, and the content of methanol in the mobile phase, on-column efficiency were evaluated. Column efficiency as high as 200 000 theoretical plates per meter for naphthalene was obtained with the optimal condition of 70% v/v methanol and 30% v/v of 10 mmol/L phosphate buffer (pH 7.8) at an applied voltage of 10 kV and a supplementary pressure of 500 psi.

Topics: Benzyl Alcohol; Buffers; Capillary Electrochromatography; Hydrogen-Ion Concentration; Naphthalenes; Reproducibility of Results; Silanes; Silicon Dioxide; Styrene; Thiourea; Toluene