Characterization of capillary inner surface conditions with streaming potential

Area of Science:

• Electrochemistry
• Surface Science
• Analytical Chemistry

Background:

• Streaming potential arises from electrolyte flow over charged surfaces.
• Fused silica capillaries exhibit measurable streaming potentials influenced by surface charge.
• Characterizing capillary surface properties is crucial for reproducible analytical separations.

Purpose of the Study:

• To investigate the influence of background electrolyte (BGE) concentration and pH on streaming potential in fused silica capillaries.
• To determine the relationship between streaming potential, surface charge, and temperature.
• To demonstrate the utility of streaming potential measurements for monitoring and mitigating analyte adsorption.

Main Methods:

• Measurements of streaming potential in uncoated fused silica capillaries using HCl, NaCl, and NaOH solutions (0.4–6 mM) at varying temperatures (15–35 °C).
• Use of buffer solutions (pH 1.5–12.7) to assess pH sensitivity.
• Calculation of zeta potentials and surface charge densities from streaming potential data.

Main Results:

• Streaming potential decreased with increasing BGE concentration, amplified at higher temperatures.
• Streaming potential showed sensitivity to pH, peaking around 9.5, with no observation below pH 3.3.
• The pH of zero surface charge shifted from 3.3 to 3.1 between 15 °C and 35 °C.
• Analyte-dependent adsorption was monitored and mitigated.

Conclusions:

• Capillary surface conditions significantly alter streaming potential.
• Streaming potential measurements provide insights into surface charge and BGE interactions.
• Mitigation of analyte adsorption through understanding surface properties enhances peak symmetry and migration time reproducibility.