Quantifying the cleanliness of glass capillaries

Area of Science:

• Materials Science
• Surface Chemistry
• Biophysics

Background:

• Patch pipets are crucial tools in electrophysiological studies.
• The lumenal surface properties of glass capillaries can influence experimental outcomes.
• Commonly used glass types include quartz, borosilicate, and high-lead glass.

Purpose of the Study:

• To investigate the lumenal surface properties of commonly used glass capillaries.
• To determine the presence and nature of surface contaminants on these capillaries.
• To evaluate the effectiveness of cleaning methods for improving surface properties.

Main Methods:

• Capillary rise measurements using water and methanol.
• Calculation of capillary rise and contact angle from weight measurements.
• Comparison of experimental rise with theoretical maximum rise assuming perfect wetting.

Main Results:

• Water's capillary rise was significantly less than theoretical maximums for all glass types.
• Cleaning methods improved water's capillary rise but did not achieve theoretical maximums.
• Methanol's capillary rise was unaffected by cleaning and remained below theoretical maximums.
• Surface contaminants varied in water solubility across glass types (Corning 7800 > quartz > Corning 0010).
• A surface film was detected in quartz tubing with an internal filament.

Conclusions:

• Borosilicate, quartz, and high-lead glass capillaries possess lumenal surface films.
• Appropriate cleaning methods can remove these films, though complete removal may be challenging.
• Surface contaminants may be unique to each glass type and potentially hydrophobic.
• Two methods are presented for quantifying the cleanliness of glass capillary tubing.
• The relevance of these surface films to electrophysiological studies remains unknown.