HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF FATTY-ACID DERIVATIVES IN THE COMBINED SILVER ION AND REVERSED-PHASE MODES

In order to learn more of the mechanism of silver ion complexation in chromatographic systems, the retention characteristics of some unsatur ated fatty acid esters (phenacyl and phenethyl) were determined using reversed-phase high-performance liquid chromatography with silver ions in the mobile phase. It was possible to calculate equivalent chain le ngth and fractional chain length values, which appeared to indicate th at double bonds and silver ions formed simple 1:1 complexes in the mob ile phase. The overall lipophilicity of the complex had an effect in d etermining the resolution of positional isomers. The equilibrium const ant for the formation of phenacyl oleate (or ''argentation constant'') was calculated to be in the range 0.059-0.067, depending on the exper imental conditions. The mechanism is compared with that for systems in which silver ions are bound to the stationary phase.