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

Column reproducibility and peak shapes are improved for polar and basi c solutes in normal-phase chromatography using new highly purified, lo w-acidity unmodified porous silica microspheres. The chromatographic c haracteristics of this new type B silica are compared with a conventio nal type A silica to determine the type and level of mobile phase modi fiers needed for good results. The effect of sample type and sample lo ading on retention, column efficiency and peak shape also was measured . Critical normal-phase tests compared this new silica with several co mmercial silicas. The new silica shows special promise for developing rugged separation methods to analyze polar and basic compounds that tr aditionally are handled by reversed-phase chromatography. Normal-phase chromatography is well-suited for highly organic-soluble compounds an d certain structures such as positional isomers.