Chemical compatibility of wetted materials 41
AZURA® Conductivity Monitor CM 2.1S Instructions, V6710
reducing solvents, inorganic acids or at higher temperatures. Maximum
operating temperature: 50 °C
Polytetrafluorethylene (PTFE, Teflon®)
PTFE is very soft and anti-adhesive. This material is resistant against
almost all acids, lyes and solvents, except against fluid natrium and fluo-
ride compounds. In addition, it is temperature-resistant from -200 °C to
+260 °C.
Systec AF™
This amorphous perfluorinated copolymer is inert against all commonly
used solvents. However, it is soluble in perfluorinated solvents like Fluo-
rinert® FC-75 and FC-40, and Fomblin perfluor-polyether solvents from
Ausimont. In addition, it is affected by Freon® solvents.
Polychlortrifluorethylene (PCTFE, Kel-F®)
The semi-crystalline thermoplastic material is plasticizer-free and dimen-
sionally stable, even in a wide temperature range
(−240
°C to +205 °C).
It
is moderately resistent against ether, halogenated solvents and toluene.
Halogenated solvents over +60 °C and chlorine gas should not be used.
Fluorinated rubber (FKM)
The elastomer consisting of fluorinated hydrocarbon stands out due to
a high resistance against mineral oils, synthetic hydraulic fluids, fuels,
aromatics, and many organic solvents and chemicals. However, it is not
compatible with strong alkaline solvents (pH value >13) like ammonia,
and acidic solvents (pH value <1), pyrrole and THF. Operating tempera-
ture: Between -40 °C and +200 °C.
Perfluorinated rubber (FFKM)
This perfluoro elastomer has a higher fluorine content as fluorinated
rubber and is therefore chemically more resistant. It can be employed at
higher temperatures (up to 275 °C). It is not compatible with Pyrrole.
12.3 Non-metals
Diamond-like carbon (DLC)
This material is characterized by a high hardness, a low coefficient of fric-
tion and thus low wear. In addition, it is highly biocompatible. DLC is inert
against all acids, alkalis and solvents commonly used in HPLC.
Ceramic
Ceramic is resistant against corrosion and wear and is fully biocompati-
ble. An incompatibility against acids, alkalis and solvents commonly used
in HPLC is not known.
Alumina (Al
2
O
3
)
Due to their high resistance to wear and corrosion, alumina ceramic is
used as a coating for mechanically stressed surfaces. It is a biocompatible
material with low thermal conductivity and low thermal expansion.
