Recent trends in monitoring of European water framework directive priority substances using micro-sensors: a 2007-2009 review

Combining Electrochemiluminescence Detection with Aptamer-Gated Indicator Releasing Mesoporous Nanoparticles Enables ppt Sensitivity for Strip-Based Rapid Tests

The combination of electrogenerated chemiluminescence (ECL) and aptamer‐gated indicator delivering (gAID) magnetic mesoporous silica nanoparticles embedded into glass fibre paper functionalised with poly(ethyleneglycol) and N‐(3‐triethoxysilylpropyl)diethanolamine allowed the development of a rapid test that detects penicillin directly in diluted milk down to 50±9 ppt in <5 min. Covalent attachment of the aptamer “cap” to the silica scaffold enabled pore closure through non‐covalent electrostatic interactions with surface amino groups, while binding of penicillin led to a folding‐up of the aptamer thus releasing the ECL reporter Ru(bpy)₃²⁺ previously loaded into the material and letting it be detected after lateral flow by a smartphone camera upon electrochemical excitation with a screen printed electrode inserted into a 3D‐printed holder. The approach is simple, generic and presents advantages with respect to sensitivity, measurement uncertainty and robustness compared with conventional fluorescence or electrochemical detection, especially for point‐of‐need analyses of challenging matrices and analytes at ultra‐trace levels.

Ultraviolet absorption of contaminants in water

Contaminants in water were studied using ultraviolet absorption with light emitting diode and deuterium lamp sources, and a thresholding detector. The absorption spectra of potassium hydrogen pthalate, clothianidin, tryptophan, thiamethoxam, uric acid and metaldehyde were obtained in the range 200–360 nm. Only metaldehyde was not suitable for detection in this range. For the other contaminants, and mixtures of pairs of compounds, the transmitted signal could be approximately described with a simple spectral model of the source–absorption–detector system. Combined measurements at two wavelengths could allow relative concentrations in certain mixtures to be determined, and real-time absorption measurements were demonstrated in a flume.

Multiplexed Detection of Analytes on Single Test Strips with Antibody-Gated Indicator-Releasing Mesoporous Nanoparticles

Rapid testing methods for the use directly at a point of need are expected to unfold their true potential especially when offering adequate capabilities for the simultaneous measurement of multiple analytes of interest. Considering the unique modularity, high sensitivity, and selectivity of antibody‐gated indicator delivery (gAID) systems, a multiplexed assay for three small‐molecule explosives (TATP, TNT, PETN) was thus developed, allowing to detect the analytes simultaneously with a single test strip at lower ppb concentrations in the liquid phase in <5 min using a fluorescence reader or a smartphone for readout. While the TNT and PETN systems were newly developed here, all the three systems also tolerated harsher matrices than buffered aqueous model solutions. Besides a single‐track strip, the outstanding modularity of the hybrid biosensor materials in combination with strip‐patterning technologies allowed us to obtain a multichannel strip in a straightforward manner, offering comparable analytical performance while allowing to be tailored even more to the user's need.

An integrated measurement of six response performance indicators for lead ion-selective electrodes and application

A heavy metal ion-selective electrode (ISE) with highly multiple response performances, rather than a high single response performance, is needed urgently for in situ, real-time environmental monitoring. In this study, we present an integrated measurement of six response performance variables such as the response slope, selectivity, dynamical range, detection limit, response time, and lifetime. They are selected and used as the indicators of the quality assessment for Pb²⁺-ISEs. The measurement, named as electrode comprehensive quality index (I_ECQ), is a single number for a given ISE. The comprehensive qualities of 114 Pb²⁺-ISEs reported in the literature were evaluated through the index method. Twenty-one Pb²⁺-ISEs-based polymer membrane with top 3 I_ECQ values for seven different properties have been recommended by evaluating and screening of the electrodes. Five Pb²⁺-ISEs-based polymer membrane with the best single response performance were also provided. The recommended Pb²⁺-ISEs, along with the corresponding Pb²⁺-ISEs with the miniaturized configurations, will provide helpful guideline for the application of Pb²⁺-ISE with highly multiple response performances in real-time environmental monitoring.

Charged Metal Nanoparticles for Chemoelectronic Circuits

Although metal nanoparticles (NPs) stabilized with self-assembled monolayers (SAMs) of various organic ligands have proven useful in applications ranging from chemical sensing, to bionanotechnology, to plasmonics and energy conversion, they have not been widely considered as suitable building blocks of electronic circuitry, largely because metals screen electric fields and prevent electrically tunable conductivity. However, when metal nanoparticles a few nanometers in size are stabilized by charged ligands and placed under bias, the counterions surrounding the NPs can redistribute and establish local electric fields that feed back into the electronic currents passing through the nanoparticles' metallic cores. Herein, the manner in which the interplay between counterion gradients and electron flows can be controlled by using different types of SAMs is discussed. This can give rise to a new class of nanoparticle-based "chemoelectronic" logic circuits capable of sensing, processing, and ultimately reporting various chemical signals.

Distributed electrochemical sensors: recent advances and barriers to market adoption

Despite predictions of their widespread application in healthcare and environmental monitoring, electrochemical sensors are yet to be distributed at scale, instead remaining largely confined to R&D labs. This contrasts sharply with the situation for physical sensors, which are now ubiquitous and seamlessly embedded in the mature ecosystem provided by electronics and connectivity protocols. Although chemical sensors could be integrated into the same ecosystem, there are fundamental issues with these sensors in the three key areas of analytical performance, usability, and affordability. Nevertheless, advances are being made in each of these fields, leading to hope that the deployment of automated and user-friendly low-cost electrochemical sensors is on the horizon. Here, we present a brief survey of key challenges and advances in the development of distributed electrochemical sensors for liquid samples, geared towards applications in healthcare and wellbeing, environmental monitoring, and homeland security. As will be seen, in many cases the analytical performance of the sensor is acceptable; it is usability that is the major barrier to commercial viability at this moment. Were this to be overcome, the issue of affordability could be addressed. Graphical Abstract ᅟ.

Determination of the priority substances regulated by 2000/60/EC and 2008/105/EC Directives in the surface waters supplying water treatment plants of Athens, Greece

An investigation into the occurrence of priority substances regulated by 2000/60/EC Water Framework Directive and 2008/105/EC Directive was conducted for a period of one year in the surface water sources supplying the water treatment plants (WTPs) of Athens and in the raw water of WTPs. Samples from four reservoirs and four water treatment plants of Athens were taken seasonally. The substances are divided into seven specific groups, including eight volatile organic compounds (VOCs), diethylhexylphthalate, four organochlorine pesticides (OCPs), three organophosphorus/organonitrogen pesticides (OPPs/ONPs), four triazines and phenylurea herbicides, pentachlorophenol, and four metals. The aforementioned substances belong to different chemical categories, and different analytical methods were performed for their determination. The results showed that the surface waters that feed the WTPs of Athens are not burdened with significant levels of toxic substances identified as European Union (EU) priority substances. Atrazine, hexachlorocyclohexane, endosulfan, trifluralin, anthracene and 4-nonylphenol were occasionally observed at very low concentrations. Their presence in a limited number of cases could be attributed to waste disposal, agricultural activities, and to a limited industrial activity in the area nearby the water bodies.

Urban domestic wastewater: how to reduce individual injection?

The present paper aims to identify ways to reduce pollution injected by residents in the urban wastewater network system. Two approaches are considered. The first one uses flow and pollutant calculation to test whether a polluter can easily be identified in a neighborhood. The second approach uses a survey to examine what incentive would be most effective to influence residents' behavior. Hydrodynamic simulation results show that concentration profiles at the network outlet corresponding to all possible polluters are similar and thus do not point out specific resident source of pollution. Household-level survey results show that most socio-economic and public-good-related characteristics do not play a significant role in explaining choices to discard in the home wastewater network. Apart from the nature of the waste itself, by far the belief that the respondent has about neighbors' and relatives' discarding behavior is the main driver of the choice.

Ultra-sensitive conductometric detection of pesticides based on inhibition of esterase activity in Arthrospira platensis

Enzymatic conductometric biosensor, using immobilized Arthrospira platensis cells on gold interdigitated electrodes, for the detection of pesticides in water, was elaborated. Cholinesterase activity (AChE) was inhibited by pesticides and a variation of the local conductivity was measured after addition of the substrate acetylthiocholine chloride (AChCl). The Michaelis-Menten constant (Km) was evaluated to be 1.8 mM through a calibration curve of AChCl. Inhibition of AChE was observed with paraoxon-methyl, parathion-methyl, triazine and diuron with a detection limit of 10(-18) M, 10(-20) M, 10(-20) M and 10(-12) M, respectively and the half maximal inhibitory concentration (IC50) was determined at 10(-16) M, 10(-20) M, 10(-18) M and 10(-06) M, respectively. An important decrease of response time τ90% was recorded for AChE response towards AChCl after 30 min cell exposure to pesticides. Scanning electron microscopy images revealed a degradation of the cell surface in presence of pesticides at 10(-06) M.

A ferrocene-porphyrin ligand for multi-transduction chemical sensor development

5,10,15,20-Tetraferrocenyl porphyrin, H2TFcP, a simple example of a donor-acceptor system, was tested as ligand for the development of a novel multi-transduction chemical sensors aimed at the determination of transition metal ions. The fluorescence energy transfer between ferrocene donor and porphyrin acceptor sub-units was considered. The simultaneously measured optical and potentiometric responses of solvent polymeric membranes based on H2TFcP permitted the detection of lead ions in sample solutions, in the concentration range from 2.7 × 10(-7) to 3.0 × 10(-3) M. The detection limit of lead determination was 0.27 μM, low enough to perform the direct analysis of Pb2+ in natural waters.

Highly luminescent Ag+ nanoclusters for Hg2+ ion detection

A simple, low-cost and label-free Hg(2+) ion sensor has been developed by using novel luminescent Ag(+) nanoclusters (NCs) with an excellent optical property (quantum yield = 15%), an ultra-high ratio of active Ag(+) species in the NC surface (~100%), and an ultra-short diffusion path length of Hg(2+) ions to access the NC surface (~0.5 nm).

Cell-based sensor system using L6 cells for broad band continuous pollutant monitoring in aquatic environments

Pollution of drinking water sources represents a continuously emerging problem in global environmental protection. Novel techniques for real-time monitoring of water quality, capable of the detection of unanticipated toxic and bioactive substances, are urgently needed. In this study, the applicability of a cell-based sensor system using selected eukaryotic cell lines for the detection of aquatic pollutants is shown. Readout parameters of the cells were the acidification (metabolism), oxygen consumption (respiration) and impedance (morphology) of the cells. A variety of potential cytotoxic classes of substances (heavy metals, pharmaceuticals, neurotoxins, waste water) was tested with monolayers of L6 cells (rat myoblasts). The cytotoxicity or cellular effects induced by inorganic ions (Ni²⁺ and Cu²⁺) can be detected with the metabolic parameters acidification and respiration down to 0.5 mg/L, whereas the detection limit for other substances like nicotine and acetaminophen are rather high, in the range of 0.1 mg/L and 100 mg/L. In a close to application model a real waste water sample shows detectable signals, indicating the existence of cytotoxic substances. The results support the paradigm change from single substance detection to the monitoring of overall toxicity.

Voltammetric Detection of Hg2+ Using Peptide-Functionalized Polymer Brushes

Polymer brushes grafted by surface-initiated atom transfer radical polymerization (SI-ATRP) from the surface of Ir-based microelectrode arrays are explored as a platform for the fabrication of sensory coatings for the voltammetric detection of Hg2+. The polymer brush coatings are post-modified with a metallothionein derived peptide to enable the selective detection of Hg2+. The performance of the polymer brush modified microelectrode arrays was evaluated using both cyclic voltammetry (CV) as well as square-wave anodic stripping voltammetry (SWASV) experiments. These studies revealed that the polymer brush based coatings allowed the selective detection of Hg2+ with detection limits in the subnanomolar range.