Portable All-in-One Electrochemical Actuator-Sensor System for the Detection of Dissolved Inorganic Phosphorus in Seawater

Abstract

We present a methodology for the detection of dissolved inorganic phosphorous (DIP) in seawater using an electrochemically driven actuator-sensor system. The motivation for this work stems from the lack of tangible solutions for the in situ monitoring of nutrients in water systems. It does not require the addition of any reagents to the sample and works under mild polarization conditions, with the sample confined to a thin-layer compartment. Subsequent steps include the oxidation of polyaniline to lower the pH, the delivery of molybdate via a molybdenum electrode, and the formation of an electroactive phosphomolybdate complex from DIP species. The phosphomolybdate complex is ultimately detected by either cyclic voltammetry (CV) or square wave voltammetry (SWV). The combined release of protons and molybdate consistently results in a sample pH < 2 as well as a sufficient excess of molybdate, fulfilling the conditions required for the stoichiometric detection of DIP. The current of the voltammetric peak was found to be linearly related to DIP concentrations between 1 and 20 μM for CV and 0.1 and 20 μM for SWV, while also being selective against common silicate interference. The analytical application of the system was demonstrated by the validated characterization of five seawater samples, revealing an acceptable degree of difference compared to chromatography measurements. This work paves the way for the future DIP digitalization in environmental waters by in situ electrochemical probes with unprecedented spatial and temporal resolution. It is expected to provide real-time data on anthropogenic nutrient discharges as well as the improved monitoring of seawater restoration actions.

Imaging of CO2 and Dissolved Inorganic Carbon via Electrochemical Acidification–Optode Tandem

“…The PANI film is activated once per sample imaging, and then, it is regenerated before being used for the next sample (10 mM H 2 SO 4 at 0 V versus the Ag/AgCl RE, Supporting Information). With this regeneration procedure, the PANI mesh can be re-used for more than 70 activations over a minimum of two weeks. , Because of the regeneration step, the principle is not suitable for continuous but for discrete dynamic and/or long-term measurements of DIC along the lifetime of the PANI–optode system.…”

“…Polyaniline (PANI) has been shown to release a significant number of protons upon its oxidation to acidify environmental samples . This phenomenon was specifically used for the detection of alkalinity and dissolved inorganic phosphorus . Moreover, in a recent letter, the combination of a PANI mesh electrode with a planar pH optode has allowed for the 2D visualization of PANI-mediated electrochemical acidification in diverse samples.…”

“… 18 This phenomenon was specifically used for the detection of alkalinity 19 and dissolved inorganic phosphorus. 20 Moreover, in a recent letter, the combination of a PANI mesh electrode with a planar pH optode has allowed for the 2D visualization of PANI-mediated electrochemical acidification in diverse samples. The concept was also used to map buffer capacity gradients in heterogeneous samples.…”

Light‐induced Delivery of Charged Species using Ion‐selective Core–Shell Nanoparticles

“…For example, once polyaniline (PANI) is electrochemically activated, it releases protons and is an efficient acidification actuator on the microscale [18] with confined local effects. [19] The operation underlying local pH changes generated by activated PANI has been modeled, and, in principle, it could be translated to the NP configuration. [20] Moreover, any conducting polymer's electrochemical, photochemical, or photoelectrochemical behavior is prone to manifest in the NP configuration.…”

“…Moreover, owing to their intrinsic semiconducting features, different electrochemical processes can be performed to modify or actuate such materials. For example, once polyaniline (PANI) is electrochemically activated, it releases protons and is an efficient acidification actuator on the microscale [18] with confined local effects [19] . The operation underlying local pH changes generated by activated PANI has been modeled, and, in principle, it could be translated to the NP configuration [20] .…”