7] Preparation of metal-free solutions for studies of active oxygen species

Abstract

8-Hydroxyquinoline (8-HOQ) is a very efficient chelator with a high binding constant for a broad range of metals. 8-HOQ has been commercially coated onto controlled-pore glass (CPG) beads; and in this form, it provides the best method for the removal of metals from all volumes and classes of reagents used in oxygen radical reactions. This chapter discusses CPG/8-HOQ method to prepare metal-free solutions for the studies of active oxygen species. CPG/8-HOQ can be used in either batch or column procedures. In the batch procedure, an amount of dry CPG/8-HOQ equivalent to about 5 times the estimated or known content of iron is weighed into the reagent solution to be demetaled and stirred or shaken for 30 minutes. The chelator is removed by centrifugation or by settling, and the reagent is decanted. The metal content is analyzed by atomic absorption (AA) spectrophotometry, and the chelation procedure is repeated if necessary. This method is simple but great care must be exercised to avoid contamination during recovery of the reagent. Column procedures offer fewer opportunities for recontaminating the reagent, but they may be less efficient than batch extractions if the elution rate from the column is too fast.