Ageing processes of alkyl bonded phases in HPLC; a chromatographic and spectroscopic approach

Summary Laboratory use of HPLC columns packed with C8 and C18 bonded phases leads to changes in selectivities and retention volumes. FTI R, 1 H N M R of hydrolysed bonded phases and solid state 13C-and 29Si NMR were applied to characterize the materials. The results of the various techniques are in fair agreement except solid state NMR. Loss of silane and hydrolysis of surface siloxane groups have been observed for the C8 bondes phase, while for the C18 material the latter process seems to dominate. The solid state NMR results have been tentatively explained in terms of changing chain arrangements and mobilities