On-site quantitative analysis of As(III) and As(V) in aqueous phase using portable laser-induced fluorescence platform.

Arsenic contaminants exist in different chemical forms with varying toxicity and mobility, making on-site analysis challenging. Here, a fluorogenic method is developed for the efficient detection of arsenite and arsenate ions using a portable platform directly in an aqueous phase. During sensing, the aggregation-induced emission (AIE) probe TPE-Cys/TPE-2Cys exhibits low fluorescence when dissolved, but reacts with the As(III) to form organic arsenic complexes with low solubility, inducing a turn-on fluorescence for quantitative analysis. Using a prior reduction strategy, the As(V) can be converted to As(III) and further analyzed in a sequential detection. Using a specialized laser-induced fluorescence instrument, this strategy allows on-site analysis of As(III) and As(V) species with sensitivity down to 0.14 ppb in environmental samples, showing that As(III) dominates while the As(V)/As(III) ratio varies in a constitutional equilibrium. The system has potential for the practical analysis of complex arsenic, revealing the dynamic arsenic transformations in the environment.