6. Recycling Preparative HPLC

6-1. Overview

It is common to improve separations by increasing the theoretical plate number with a long column, however, the column length is restricted by the maximum operating pressure. Recycling preparative HPLC is a technique to artificially extend the column length by repeatedly injecting the eluted solution. For example for a 15 cm long column
providing 10,000 plates, if the eluted solution is recycled once, the column corresponds to a 30 cm long column providing 20,000 plates. If the eluted solution is recycled five times, the column corresponds to a 75 cm long column
providing 50,000 plates.

6-2. Suppression of Peak Distortion in the Recycling Process

The volumes of the sample loop and the preheat mixer are large in preparative HPLC because of the high flow rate. However, it is necessary to temporarily remove them from the flow path to minimize peak dispersion. Our preparative HPLC system performs this by two valves. We call it Dead Volume Cut System (DVCS), and it dramatically improves the efficiency of preparative HPLC.