How to Cut a Metal Capillary GC Column
When doing gas chromatography, it is important to get a clean square cut for your metal MXT capillary GC column. A good cut is an integral part of making sure you have proper column installation and leak-free connections, and a ceramic scoring wafer is the right tool for this job.
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Let’s talk about the best way to cut a metal capillary GC column. If we follow just a few simple steps, we’re on our way to good chromatography every time.
Before we start, we should always straighten the column ends. Run the ends between your fingers while bending against the curve until the column is perfectly straight. This step is extremely important because hooked or bent columns will be difficult to install and can lead to inconsistent sample transfer, analyte activity, and poor reproducibility. Then, just like you would install a fused silica capillary column, place the column nut and correct size ferrule onto your column.
To cut the column we will use a ceramic scoring wafer. Run your fingernail on the side of the scoring wafer to find the smooth edge. Place the column on your finger and position the smooth edge of the scoring wafer at approximately 45 degrees. Use mild pressure to score the column with a sawing motion. Typically, 4 “saw-moves” should be enough. Next, place the scoring wafer beneath the score and use it to bend the column away from the score and then back again. The column will snap in two pieces. The ends can be polished with the sides of the scoring wafer. Inspect the column end, looking for a straight cut and good column shape. Clean the column ends with lab wipes moistened with isopropanol to remove any metal debris. Your column is now ready for installation.
There are a few things to watch out for. Using too much force during the cut will flatten the end creating an oval shaped column. This will damage the needle during on-column injections, or lead to poor sample transfer during the injection process. Additionally, scoring metal columns will dull the ceramic wafer over time. The edges might become uneven and the scoring wafer will eventually have to be replaced. I always like to have two scoring wafers: one for metal columns and the other one for more fragile fused silica columns. It’s as simple as that: straighten the column ends and don’t push too hard when scoring and you will be on your way to good chromatography.
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