there are several other advantages to using the direct detection mode of affinity chromatography.Another factor that leads to the good preci- sion in HPLC-based affinity methods is the reduced batch-to-batch variation, which is the result of using the same ligand for the analysis of multiple samples and calibrators.In some cases, there have been reports were affinity columns have been used for .1000 injections with no serious signs of degradation (2,5,6)1) (2, 4, 5 ).