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.
An assortment of needle files can be used to pick out ferrules from fittings, remove burrs, and shape the ends of metal tubing
before it is connected to a fitting. Don't forget to clean off all traces of metal before connecting.
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.
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.
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 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.