Skip to main content
Chemistry LibreTexts

2. Cutting a New Capillary

Since most vendors sell bare-fused silica capillaries on spools, it will be necessary to cut a length of capillary for use with the Homebuilt CE system. Cutting a capillary takes practice; therefore it is recommended that smaller lengths (10-15cm) of capillary are used at first. Also be aware of the potential projectile hazard associated with breaking fused silica capillaroes. It is recommended that protective eyeware be worn while cutting a capillary.

  1. Measure the desired length of capillary from the spool. Mark this length on the polyimide coating of the fused-silica capillary using a soft-tip marker.
  2. Using a ceramic capillary cutter, score the capillary at the mark using a firm, but even pressure at a 45° angle to the capillary. The scoring should be done with one distinct motion. DO NOT use the capillary cutter to saw the capillary. Once scored, the capillary may be snapped from the spool using a gentle bending pressure.
  3. Next, measure and mark the location of the detection window. For use with the Homebuilt CE system, the detection window should be located approximately 8 - 9 cm from one end of the capillary. Commercial instruments may require a different location for the detection window.
  4. Bend the capillary into a loop with the detection window at the apex. Using a match or a cigarette lighter on its lowest setting, hold the flame to the region of the detection window until the polyimide glows red and chars (about 1 sec). It is important to practice this step on scrap capillary. The detection window should be approximately 1.5-2mm wide. Larger detection windows will have adverse affects on analyte detection.
  5. Wet a disposable wipe with deionized water and GENTLY wipe the soot from the window. The exposed bare-fused silica is very fragile, so avoid touching and bending the capillary at the detection window. The capillary is now ready to be placed into the UV-vis absorbance detector.