The toxicity and bioavailability of Cu in seawater were estimated using its chemical speciation. In this study, the concentrations and conditional stability constants (K'_CuL) of Cu complexes with Cu-binding organic ligands (L) in seawater were determined using the reverse titration–competitive ligand exchange–adsorptive cathodic stripping voltammetry method. The concentrations of strong and weak ligands (L₁ and L₂, respectively) were determined using reverse titration via the addition of Cu to seawater samples to achieve ligand saturation. Our results revealed that the reverse titration method can be successfully used for the detection of high concentrations of L₂. Using the reverse titration method, we detected L₂ concentrations that exceeded 80 and 120 nM in seawater samples from the subtropical western North Pacific Ocean and Otsuchi Bay Japan, respectively. The K′_CuL1 and K′_CuL2 values obtained using the reverse titration method were comparable with those obtained using the forward titration method. Therefore, the reverse titration method can be used to determine the chemical speciation of Cu in the ocean and coastal regions as supplement to the more conventional forward titration method.

铜在海水中的毒性和生物利用度通过化学形态估算。在这项研究中，浓度和条件稳定性常数（K” _CUL使用测定的Cu络合物的与海水的Cu结合的有机配体（L））的反向滴定竞争配位体交换吸附性阴极溶出伏安法的方法。通过将铜添加到海水样品中以实现配体饱和，使用反向滴定法测定强和弱配体的浓度（分别为L ₁和L ₂）。我们的结果表明，反向滴定法可成功用于检测高浓度的L ₂。使用反向滴定法，我们分别从北亚热带西太平洋和日本大月湾的海水样品中检测到L ₂浓度分别超过80和120 nM。所述ķ ' _{CUL 1}和ķ ' _{CUL 2}使用反向滴定法分别与使用正向滴定法获得的那些可比较的所获得的值。因此，作为更常规的正向滴定法的补充，反向滴定法可用于确定海洋和沿海地区的Cu的化学形态。