Effect of buffers on silica-based column stability in reversed-phase high-performance liquid chromatography

Previous studies have shown that bonded-phase packing degradation at pH 9–10 mainly is due to silica support dissolution, and does not primarily result from the hydrolysis of covalently attaching siloxane bonds. Column stability also is significantly affected by the type and concentration of organic mobile-phase modifier. We now find that silica-based bonded-phase packings variably degrade with buffers containing different anions and cations. This effect is especially apparent with intermediate- and high-pH buffers. Under the same conditions, pH 10 aqueous carbonate and phosphate buffers with 50% methanol degraded bonded-phase packings much faster than borate and glycine buffers. The nature of the buffer cation also influences bonded-phase packing stability, with column lifetime a function of sodium> potassium> ammonium cations. The rate of bonded-phase packing degradation at pH 7–10 increases with higher concentrations of certain buffers, but especially phosphate. Column degradation is very strongly influenced by temperature. Certain mobile phase-buffer conditions can lead to increased column lifetime, so that practical operation up to pH 10 appears possible for some silica-based columns.