BATCH-TO-BATCH VARIATION OF CHELEX-100 CONFOUNDS METAL-CATALYZED OXIDATION, LEACHING OF INHIBITORY COMPOUNDS FROM A BATCH OF CHELEX-100 ANDTHEIR REMOVAL BY A PRE-WASHING PROCEDURE

Removal of adventitious redox-active metals from buffers by treatment with Chelex resin is a widely used procedure in free radical research. Use of a new batch of Chelex-100 resin in our laboratory coincided wi th a sudden inability to oxidise low-density lipoprotein with copper. We found that copper-mediated oxidation of ascorbate in water treated with the same batch of Chelex was inhibited when compared with untreat ed water and water treated with a different batch of the resin. Washin g the Chelex removed the inhibitory effect suggesting that material wa s leaching from the resin. The washing procedure for Chelex-100 descri bed is simple and can be scaled up. Oxidation of ascorbate with low co ncentrations of copper can be used to test the quality of batches of t he resin.