Ferrules, Metal Tubing

Ferrules for metal tubing are also essential. I used to prefer brass ferrules for copper and stainless-steel tubing, but nowadays I match the ferrule material to the tubing because some brass ferrules will bind to stainless steel upon tightening. Some instruments use 1/16-in. or 3/32-in. stainless tubing. This tubing is best connected using 1/8-in. graphite–Vespel reducing ferrules for 1/8-in. fittings, or 1/16-in. ferrules for the 1/16-in. tubing. Chromatographers should be aware of the potential for atmospheric oxygen contamination of the carrier gas from improperly installed supply tubing and ferrules. Even with the best filtration in place, a leak between the filters and the instrument will nullify the effect of the filters.

Files, Needle

Flexible Magnetic Pickup

A flexible 2-ft magnetic pickup comes in handy when you drop a small part inside the instrument. Another similar tool has a three-jawed "claw" operated by a plunger, and it will pick up nonmagnetic items.

Flowmeter, Electronic

An electronic flowmeter is an expensive investment, but I believe that it will pay for itself many times over with improved accuracy and precision over bargain-priced bubble flowmeters. I prefer the type of electronic meter that senses flow directly and that allows the operator to select the type of gas in use, such as air, helium, or hydrogen. The option to calculate split ratios from the measured split vent and column flows is a handy feature.

Flowmeters, Bubble

If you use bubble flowmeters, keep two sizes on hand. The large size is good for measuring FID air or inlet split vent flows up to several hundred milliliters per minute. The smaller size is better for packed-column or hydrogen flame-gas flows in the 10–50 mL/min range. Don't try to use a bubble flowmeter to measure capillary column flows below 10 mL/min. The carrier gas will diffuse out of the bubble and you will get a low reading. Measure the unretained peak time instead and calculate the flow rate from it. Note that this calculated flow rate or the rate displayed by electronic pressure control will only be as accurate as the column dimensions the operator uses. See an earlier "GC Connections" (2) for a detailed discussion.

Glass Wool Insertion and Removal Tool

This item is useful for those who must install glass wool in inlet liners, or for the hardy few who pack their own columns and use glass wool to hold in the packing. These days I find little use for it.

Inlet Liners

Inlet liners are often broken or chipped during installation or removal. They also can become contaminated with sample residue or may lose their deactivation if used for too long at high temperatures. Keep some spares on hand, both for packed inlets and for split or splitless injections. If you use deactivated liners, it is better to purchase them already deactivated than try to treat them yourself because of the chemical hazards and waste disposal problems this will create.

Inlet Liner Removal Tool

A tapered high-temperature silicone rubber tool on a metal holder does a good job of grabbing glass inlet liners and removing them without cracking or chipping the liner top. Most GC instrument manufacturers will supply specific tools and instructions for a particular inlet option.