Metallothioneins (MTs) are widely used as biomarkers in environmental studies. However, eliminating interfering
factors for MT determination in vivo by electrochemical detection is difficult. In this study, NO3
− and Cl− were
found to negatively affect MT determination in Daphnia magna by square wave cathodic stripping voltammetry
(SWCSV). The relevant mechanism was analyzed, and results were used to modify the original electrochemical
testing parameters and environmental conditions. This modified SWCSV achieved accurate MT concentrations
in D. magna, leading to detection limits as low as picomolar levels.