DETERMINATION OF FREE AND BOUND CD, ZN, CU, AND AG IONS IN LOBSTER (HOMARUS-AMERICANUS) DIGESTIVE GLAND EXTRACTS BY GEL CHROMATOGRAPHY FOLLOWED BY ATOMIC-ABSORPTION SPECTROPHOTOMETRY AND POLAROGRAPHY

Gel-permeation chromatography followed by atomic absorption spectropho tometric and polarographic analyses were used to measure free and boun d divalent metal ions in lobster digestive gland extracts prepared wit h or without alpha-toluenesulfonyl fluoride, a protease inhibitor. Chr omatography on Sephadex G-50 or G-100 yielded 3 UV-absorbing peaks, wh ich corresponded, respectively, to the void volume, a medium molecular weight fraction, and a low molecular weight fraction that contained f ree divalent metal ions. In protease-inhibited extracts, only Zn+2 was found, whereas Cd, Cu, and Ag were bound in high and medium molecular weight fractions. Cd+2 and Zn+2 were rapidly released from their boun d forms in the absence of a protease inhibitor, and their presence was confirmed by polarography with EDTA. Gel-permeation chromatography co upled with atomic absorption spectrophotometry offers a rapid method f or following changes in the concentrations of bound and free metal ion s during processing of shellfish-based foodstuffs.