Polymer fittings and ferrules have proven to be superior to stainless steel in many analytical applications. IDEX Health & Science has compiled the following solvent compatibility information for polymers commonly used in HPLC.
1 PPS solvent resistance assumes room temperature use. Elevated temperatures may result in a significant reduction in chemical resistance.
2 While the solvent compatability of FEP & PFA is virtually identical, please note the temperature rating differences between them.
M Some solvents in this catagory are satisfactory, others are not. Please review the notes above or contact Upchurch Scientific for further information.
NR Solvents in this catagory are generally not recommended for use with this polymer.
* Shear strength
** In some cases, PEEK fittings can be used to 150 °C. Please contact Upchurch Scientific for specific information.
Delrin® Acetal Resin
Delrin has excellent chemical resistance to most organic solvents. This polymer’s high tensile strength also permits superior threads that are very resistant to wear. Delrin is not suitable for use with acids, bases, or oxidizing agents.
PCTFE has excellent chemical resistivity. Only THF and a few halogenated solvents will react with it. This resilient polymer is excellent for fittings and sealing surfaces.
PEEK polymer has excellent chemical resistance to organic and inorganic liquids. Concentrated sulfuric acid and concentrated nitric acid are the only commonly used solvents that will chemically attack it. PEEK tubing is not recommended for use with methylene chloride, DMSO or THF due to a physical swelling effect. However, these chemicals do not adversely affect fittings. PEEK is a hard, yet slightly flexible polymer. It is excellent for nuts, ferrules, unions, valves, tubing, etc.
Polypropylene is a very soft polymer and is generally used in low-pressure applications. Polypropylene is excellent for aqueous solutions; however, it is attacked by chlorinated, aromatic, and some organic solvents.
Polyphenylene sulfide is relatively new to the analytical lab equipment market. PPS has excellent chemical resistance to most organic solvents at room temperature. However, it is not recommended for use with chlorinated solvents, inorganic acids or any solvent at elevated temperatures (see table above). PPS is a hard polymer offering excellent thread integrity.
These polymers are inert to virtually all chemicals used in HPLC. FEP is a good choice for tubing used from the reservoir to the pump and from the detector to a waste reservoir. PFA is a higher-purity member of this polymer family and can be used for tubing in sensitive applications as well as for molding low pressure fittings.
Tefzel is a member of the fluoropolymer family that is good for sealing surfaces. Tefzel is extremely resistant to chemical attack. However, some chlorinated chemicals will cause a physical swelling of Tefzel tubing. Tefzel tubing has slightly higher pressure capabilities compared to PTFE tubing, due to a higher tensile strength.