Begin by sonicating the glass capillary tubes using an alkaline optical detergent for optical components. To do so, take the required number of glass capillary tubes and place them in a tall, narrow container, such that the capillaries do not lie flat on its base. Add a 1%alkaline detergent solution in deionized water to the container, ensuring it just covers the capillary tubes.
Tap to eliminate any trapped air bubbles from within the tubes. Loosely cover the container. Place the covered container upright in the bath, ensuring the covered does not contact the bath's water.
Sonicate the tubes at 40 degrees Celsius for 30 minutes before turning off the bath's heating element, then thoroughly rinse the capillaries with deionized or ultrapure water at least five times, discarding the rinsed water after each cycle. Next, add isopropanol or ethanol to the glass capillaries in the container so that the liquid level is just above the capillary tubes. After ensuring the absence of trapped air bubbles in the tubes, loosely cover the container.
Sonicate the capillaries as demonstrated previously for 15 to 30 minutes. After properly disposing the alcohol, dry the capillaries under nitrogen, while handling them with lint-free tissue.
