Source: "Ultrasensitive Impurity Profiles by Displacement Chromatography (American Biotechnology Laboratory Oct 2007)
Displacement chromatography with displacers (i.e. Isolis™) is effective in increasing the detection sensitivity in impurity profiles. Why would this matter?
In method transfers and scale-up, the impurity profile of the new and reference process are often compared. Often process design and control strives for consistency; thus any change is undesirable. This is especially true in purification schemes involving multiple units or steps.
A typical impurity profile of a mixture of ß-lactoglobulin A and B by ion exchange chromatography is presented in the following figure 1.
It shows two main peaks and four, perhaps five, minor peaks. This is typical of impurity profiles reported for many proteins, including therapeutics. The low level of impurities builds confidence that the purification scheme has worked well.
Displacement chromatography can be used to purify proteins, as shown in the histogram below. Conventional HPLC runs are complete in about one hour. A DC study of impurity profile is a two-step process. The first step is running the DC, including a collection of appropriate fractions. The second step is analysis of the fractions, which can be time consuming.
The center cuts of the DC give 85-86% recovery of a 99.9% pure products. This can be useful in laboratory and process scale preparation. However, DC also concentrates the impurities in the regions between the major peaks (see A-F). Analysis of the fractions from DC shows that these contain 23 impurities. Twelve of the peaks have been identified as related lactoglobulins, and 11 are unknown impurities.
Displacement chromatography increases the peak count in impurity profiles by threefold, and the measured level of impurities by about 33%.
Read the complete technical article in American Biotechnology Laboratory: