Influence of alkyl chain length on the stability of n-alkyl-modified reversed phases. 2. Model dissolution study

A dlrect, In situ study of the hydrolysis and dissolution of various n-alkyl modHied phases was performed with =Si maglc angle spinnlng NMR spectrometry as a model for statlonary phase aging In laboratory practice. WRh thls study, the substantlal effect of the ligand length on the dlssolutlon reactlon of the alkyl "ed phases under aggresslve eluent conditions is conflrmed. As expected, longer n-alkyl ligands gradually show better substrate shleldlng properties. Above a certaln critical ligand length, shielding by longer ligands inhibit the dissolution rate drastically by affectlng the hydrolysis and dissolution processes. The type of solvent system used, In tiquki chromatography practice or for dissolution studies as reported here, mainly affects the proportions of dissolved silicates in the eluent. On the basis of thls in sltu dlssolutlon study a model for ligand and substrate hydrolysis and dissolutlon with the involved reactions is presented.