The other day a customer asked me about our GC capillary tubing specifications, and was surprised to learn that the outside diameter (OD) of both 0.25 mm and 0.32 mm internal diameter (ID) MXT tubing is the same (0.41 mm), while our 0.28 mm ID MXT tubing has an OD of 0.56 mm. He was not the first person surprised with those facts. For reference, the table below lists tubing ID, OD and OD +/- ranges.
Another common question we get asked in tech service is which product we recommend for cutting GC capillary tubing. I personally suggest a ceramic wafer (pictured below is catalog number 20116). What you may not know is that these wafers have four smooth edges for cutting fused silica tubing (using a single, gentle scoring motion) and four serrated edges for cutting MXT tubing (using a firmer, sawing motion). So how can you tell which edges are smooth and which are serrated? A good magnifying glass is helpful.
One last common question concerns the color of fused silica tubing. Keep in mind that fused silica is actually a clear glass; the color you observe is caused by the polyimide coating (which gives the tubing its flexibility). Colors can range from a bright yellow to black. Don’t be concerned if your columns vary in color, performance is not affected.
I hope you have found this post helpful. Thanks for reading.