Stability problems of polyether ether ketone and ethylene-tetrafluoroethylene copolymer tubing in simulated moving bed operation

Polymeric capillaries made from polyether ether ketone (PEEK) or ethylene-tetrafluoroethylene copolymer (Tefzel) are considered as highly inert and chemically resistant materials used as standard equipment in HPLC and simulated moving bed (SMB) applications. During several racemate separations using a SMB unit equipped with these tubes a formation of micro-holes was observed. All separations had in common that a high content of an alkane was used in the mobile phase. The patterns of damage and possible reasons causing the leakages of the capillaries are discussed. Polymeric tubing had to be replaced by stainless steel capillaries for the enantiomer separations in order to ensure safety of workers, GMP status of products and control leakages.