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Fused Quartz for GC Liners?

Question asked by Stephen Griffin on Jun 5, 2014

g/cubic cmslightly Is it just me, or do others agree that we should be using quartz to make injection port liners? I know that 'the experts' say it is 'too expensive' or 'too hard to shape', but I work with quartz almost exclusively and I know that these excuses are not necessarily true. Even if quartz is a bit more expensive, don't quartz' properties justify a little more cost? Since quartz liners should last longer, the net result is very probably going to be substantial savings, anyway.

 

If you haven't considered the advantages of quartz, allow me to point out a few of them. (There are actually more reasons for using quartz in liners than there are for fused silica in columns.)

 

Terminology note: In the glass world, fused "quartz" refers to SiO2 made by fusing pure quartz sands while fused "silica" refers to a layered produce made by consolidation of SiO2 soot produced by hydrolysis of SiCl4 and such. Lab grade borosilicate glasses are extremely similar but there are wider variations that fall under "borosilicate" that I won't consider here.

 

Reactivity

Fused quartz has less than 2ppm of heavy metals contaminants where borosilicate glass has 500X more heavy metals at ~1ppt.

(Fused silica used to make GC capillary has ~0.2ppm heavy metals.)

 

Activity

Fused quartz has ~0.0005 to 0.015 Si-OH groups/square nm of surface where borosilicate glass has ~2.8 Si-OH/square nm.

(Fused silica used to make GC capillary has about 0.2 Si-OH/square nm.)

 

Vapor Production

For liners, the lower specific heat capacity (and density) of quartz combined with a >25% higher thermal conductivity makes it quite a bit better for vaporizing injected samples (772J/kg-K vs. 800 J/kg-K, 2.203g/ml vs. 2.23g/ml, and 1.4W/m-K vs. 1.1w/m-K, respectively).

 

Thermal Shock and Normal Use

More and more chromatographers are unloading and loading liners hot to save time. Borosilicate glass shatters with a sudden 160C temperature change but it takes more than 1100C change to harm fused quartz. Corning states the maximum normal use temperature for borosilicate at 230C and Heraeus states 1250C for fused quartz.

 

Damage Resistance

Fused quartz is ~50% harder than borosilicate glass so you can't scratch quartz with borosilicate wool.

 

Deactivated borosilicate is very probably more active and reactive than bare quartz and deactivation always degrades with use...For most separations, bare quartz should be inert enough and with no deactivation layer breaking down, one potential source of ghost peaks or baseline drift is eliminated. We've run endrin/DDT with bare quartz with very good results.

 

Quartz is easy to clean, too, so liners could be readily reused.

 

For the uber cautious, a deactivated quartz liner's inertness couldn't degrade very much since the worst case is better than most brand new borosilicate liners.

 

So why aren't we using fused quartz liners?

 

Don't tell me its because we can't make them...I've made single and double taper/goosenecks, "focus" liners, DI press fit types and cyclo splitters for my HP 5890 II. And don't tell me that they're too expensive...I'll sell you some for the same price as the borosilicate versions.

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