Determination of metallothionein in Daphnia magna by modified square wave cathodic stripping voltammetry

• Certain inorganic anions exerted an unexpected effect during MT determination by SWCSV.
• An accurate MT concentration in D. magna was determined using the modified SWCSV.
• A low detection limit comparable with other immunoassays was also obtained.

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.