A GC Troubleshooter's Toolkit - - Chromatography Online
A GC Troubleshooter's Toolkit


LCGC North America
Volume 7, Issue 30, pp. 570-577

Cutters, Fused-Silica Column

The best fused-silica column cutting tool is the one that holds the column in an adjustable chuck and cuts with a diamond chip as the operator rotates a thumb wheel. This tool also has a magnifying glass on the opposite end for inspecting the fresh cut for squareness and lack of burrs or hanging polyimide coating. A pen-like tool with a sapphire tip or ceramic scoring wafers or scribes that make a sharp cut on the column so that it may be broken cleanly in two are the best inexpensive alternatives. In any case, a fresh cut should be made and inspected just before placing the column into the inlet or detector and after sliding on the nut and ferrule.

Cutters, Tubing

A large plumber's tubing cutter for 1/4-in. metal tubing and a smaller one for 1/8-in. tubing are used extensively during instrument installation and gas-supply setup. The correct 1/8-in. size cutters are available from some chromatography supply companies — don't try to use the mini cutters found in home supply stores. Keep a supply of new cutter blades on hand. These disks wear out rapidly, and a dull blade will distort the tubing diameter and make it difficult to slide on the back and front ferrules. Power cutters with high-speed rotary abrasive cutting wheels are also available. These are mandatory for cutting 1/16-in. tubing for low-dead-volume gas valving applications, and they work well for any tubing up to 1/4-in. diameter. After cutting and squaring the tubing (see "Tubing Reamer" and "Deburring Tools" below) be sure to clean out the ends with a solvent such as isopropanol so that loose particles can't get into the instrument components or interfere with the passage of peaks through column ends.

Deactivated Fused-Silica Tubing

Gas chromatographers can use 5 or 10 m of deactivated 0.53-mm i.d. fused-silica tubing with a press-fit connector as a retention gap when necessary. Shorter pieces can act as a column-to-detector adapter when you don't want to put the coated column end into a detector to avoid column bleed from the column end at hot internal detector temperatures.

Dental Mirror

A plastic dental mirror with a front-silvered surface makes it easy to examine the underside of an inlet fitting in the oven, or to check other inaccessible areas for loose or missing parts. The mirror can also be used to detect the flame in a flame ionization or flame photometric detector by observing condensation of emitted water vapor on the cool mirror surface. A shiny wrench is a good substitute for the mirror in this case.

Dental Pick

A dental pick is very handy for removing septa from septum nuts and debris such as bits of graphite ferrule from fittings.

Diagonal Cutters

Diagonal cutters are used only for cutting electrical wires. They should not be used as a substitute for a tubing cutter. Don't even think about threatening your fused-silica column with one!

Eyedropper, Plastic

I have a box of these that is in frequent demand. I use them to place small drops of isopropanol onto fittings for leak checks. Some types have rough volume indications more like a pipette, and I have used them to make a crude dilution of qualitative test mixtures when accuracy wasn't required.

Ferrules, Capillary Column

A good assortment of graphite and graphite–Vespel capillary column ferrules is essential. Keep at least 10 of each inner diameter in the fitting sizes that match your instruments' oven fittings. In a pinch, graphite ferrules can be squeezed into sealing on smaller columns than they were designed for. It's always a good idea to install new ferrules with a new column; old ferrules can be reused on the same column if a seal can be made without over-tightening the fitting.


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