EXPERIMENTAL-STUDY ON THE SEPARATION OF SILICA-GEL SUPPORTS BY GRAVITATIONAL FIELD-FLOW FRACTIONATION .2. SAMPLE PREPARATION, STOP-FLOW PROCEDURE AND OVERLOADING EFFECT

Two kinds of silica were studied: a commercial porous chromatographic support with a broad size distribution and a special non-porous silica with a very narrow size distribution. The preparation of sample suspe nsions in aqueous solution of the non-ionic detergent Tween 60 was opt imized and the influence of the amount of particles injected and of th e stop-flow time on separation was investigated. A study of the overlo ading effect showed a dramatic increase in the mean retention ratio wi th increasing amount of particles. Considering previous observations, an explanation of the overloading effect in gravitational field-flow f ractionation is suggested.