How to Cleave Fused-Silica Tubing for Nano-LC/MS


Diamond ScribeDiamond tip

(Left) Diamond-chip bladed scribe.(Right) Close-up view of standard diamond-chip scribe (90 deg)

Proper cleaving of fused-silica tubing is a critical but often overlooked operation in the preparation of emitters and columns prior to use. A flat, smooth cleave is essential for maintaining low dead volume connections with other sections of fused-silica tubing. It is also critical that cleaving does not generate flow-stopping particulate matter. Cleaving is best accomplished with a high-quality diamond chip or blade cleaving tool. New Objective’s diamond-blade cleaving tools, shown in Figure 1, have been selected to provide a consistent, flat cleave with a minimum of particulate generation. Inexpensive carbide scribing tools and ceramic wafers are not recommended, since they generally result in poor-quality (i.e., ragged) cleaved end faces that generate many fine particles.

WARNING: Handling of fused-silica tubing and emitters can result in serious personal injury, including skin and eye injury. Use safety glasses or goggles meeting ANSI Z87.1-1989 requirements or the equivalent. Puncture- and chemical-resistant gloves should be worn at all times.

Correct procedure for using diamond-bladed scribe

(A) Improper cutting angle (B) Align cleaving tool blade perpendicular to tubing (C) Press down gently, scoring tubing (D) Too much downward pressure will crush tubing, producing particles that can cause tubing to clog

Procedure

  1. Place the tubing to be cut on a flat, clean surface and position the cleaving tool perpendicular to the tubing surface, as shown in Figures 1B and 2C. The long axis of the blade should be perpendicular to the tubing bore (Figure 2B).
  2. Gently press straight down; DO NOT use a sawing motion when pressing the blade. You only need to nick the surface of the polyimide coating (Figure 3C). Be careful not to force the blade through the tubing, which will generate a ragged end and many particles (Figure 3D).
  3. Pull gently on the tubing along its axis; it should easily separate at the point of contact. If it does not, repeat the procedure with a little more force. A typical cleave of 360 µm OD, 75 µm ID fused-silica tubing is shown in Figure 4. Residual surface irregularity is on average less than or equal to 10 µm.

Inspection of the distal end of the tip for a flat end and/or particle contamination using a light microscope with transmitted light at 100x magnification is highly recommended. Leaving a burr (or "tang") will cause particulate generation when tubing is inserted into standard capillary connectors.

Cleanly cleaved tubing

Cleanly cleaved tubing is clearly seen under light microscopy at 10X


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