Response of the Cu(II) ion selective electrode to Cu titration in artificial and natural shore seawater and in the measurement of the Cu complexation capacity.

Abstract

The Orion 94-29 Cu(II) jalpaite ion selective electrode (Cu-ISE) was used to measure both the concentration of the aqueous free Cu(II) ion ([Cu(II)aq]) and its changes due to additions of Cu, in artificial seawater (ASW) and in seawater from San Diego Bay, CA. The range of free copper ion (i.e., pCu, -log [Cu(II)aq]) determined in seawater samples from the San Diego Bay area (11.3-12.6, 11.9 +/- 0.4, average +/- SD) is consistent with that previously reported for estuarine and coastal areas (10.9-14.1). The changes in [Cu(II)aq] as a result of the additions of Cu were used to determine the Cu complexation capacity (Cu-CC), which has a measured range (2.7 x 10(-8)-2.0 x 10(-7) M; 7.6 x 10(-8) +/- 4.8 x 10(-8) M) comparable to the range of values previously reported for estuarine and coastal zones (i.e., L1+L2, 1.1 x 10(-8)-2.0 x 10(-7) M). The narrow range of pCu at the Cu-CC (pCuCu-CC, 11.1-11.9, 11.5 +/- 0.2) indicates the predominant role of the Cu-CC in regulating the concentration of ambient Cu(II)aq to a level < or =1 x 10(-11) M Cu(II)aq. These results attest to the capability of the Cu-ISE to measure pCu and Cu-CC in aquatic coastal environments with relatively high total Cu concentrations and organic loads, such as those from heavily used coasts and bays.