Simultaneous electrochemical detection of ciprofloxacin and Ag(I) in a silver nanoparticle dissolution: Application to ecotoxicological acute studies

Abstract

The combination of the indiscriminate use of antibiotics such as ciprofloxacin (CIP) and the recent use of biocides such as silver nanoparticles (AgNPs) that are eventually disposed of in the environment can negatively impact on aquatic biota. This work aims to develop a simple electrochemical method to detect CIP, AgNPs, and their mixtures (CIP–AgNPs) concentrations and to correlate them with the ecotoxicological effects in acute toxicity bioassays (48 h) using the microcrustacean Ceriodaphnia dubia as a test organism. The simultaneous electrochemical detection of CIP and Ag(I) in AgNP dissolution was performed by square wave anodic stripping voltammetry (SWASV) using a bismuth film electrode (BiFE). The analytical performance in the linear range was from 8 to 200 ng L−1 (R2 = 0.993) for CIP and from 104 to 3300 ng L−1 (R2 = 0.995) for Ag(I). The limits of detection (LODs) were 3 and 34 ng L−1 for CIP and Ag(I), respectively. The method was applied to the measurements of Ag(I) in the supernatant of AgNP suspensions and the study of the stability of CIP and Ag(I) from AgNPs during acute tests of C. dubia at 48 h. The median lethal concentration (LC50) of C. dubia in the presence of CIP, AgNPs, and CIP–AgNPs was calculated, and the toxicity decreased as follows: AgNPs > CIP–AgNP mixture > CIP. The lower toxicity of AgNPs in mixture with CIP could be explained by the complexation of metal ions with quinolones, decreasing their interaction with the test organisms. The stabilities of CIP and Ag(I) from AgNPs in ecotoxicology assays were estimated by measuring their concentrations by SWASV, and their values ranged from 80% to 120% from the nominal values, according to the OECD recommendation. As a perspective, the results of the work showed that the simultaneous use of stripping voltammetry and toxicity tests could be applied to the study of natural water samples and potentially to the monitoring of environmental quality. The relevance of electrochemical and ecotoxicology approaches as useful tools to contribute knowledge to preserve environmental health is highlighted.