NORMAL-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH HIGHLY PURIFIED POROUS SILICA MICROSPHERES

Column reproducibility and peak shapes are improved for polar and basic solutes in normal-phase chromatography using new highly purified, low-acidity unmodified porous silica microspheres. The chromatographic characteristics of this new type B silica are compared with a conventional type A silica to determine the type and level of mobile phase modifiers needed for good results. The effect of sample type and sample loading on retention, column efficiency and peak shape also was measured. Critical normal-phase tests compared this new silica with several commercial silicas. The new silica shows special promise for developing rugged separation methods to analyze polar and basic compounds that traditionally are handled by reversed-phase chromatography. Normal-phase chromatography is well-suited for highly organic-soluble compounds and certain structures such as positional isomers.