This study centers on the development and characterization of an innovative electrochemical sensing probe composed of a sensing mesoporous functional sol-gel coating integrated onto a glassy carbon electrode (sol-gel/GCE) for the detection of NH3 and/or NH4+ in water. The main interest for integrating a functional sol-gel coating onto a GCE is to increase the selective and sensing properties of the GCE probe towards NH3 and/or NH4+ ions. The structure and surface morphology of the newly developed sol-gel/GCE probe were characterized employing scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and Fourier-transform infrared (FTIR), while the electrochemical sensing properties were evaluated by Berthelot\'s reaction, cyclic voltammetry (CV), and adsorptive square wave-anodic striping voltammetry (Ads SW-ASV). It is shown that the newly developed sol-gel coating is homogeneously deposited on the GCE with a sub-micron and uniform thickness close to 630 nm and a surface roughness of 25 nm. The sensing testing of the sol-gel/GCE probe showed limits of detection and limits of quantitation of 1.7 and 5.56 nM of NH4+, respectively, as well as a probe sensitivity of 5.74 × 10-1 μA/μM cm-2. The developed probe was fruitfully validated for the selective detection of NH3/NH4+ in fresh and sea water samples. Computed Student texp (0.45-1.25) and Fexp (1.69-1.78) (n = 5) tests were less than the theoretical ttab (2.78) and Ftab (6.39) at 95% probability.

BACKGROUND: Mercury is one of the most toxic heavy metal contaminants that can be harmful to human health through the food chain. Recently, the colorimetric detection of heavy metals based on nanozyme catalytic activity has received extensive interest due to the simplicity, signal visibility and suitability for in situ detection. However, the majority of these nanozymes that can be utilized for detecting mercury with high synthesis temperature and complicated synthesis methods, which limited their practical application.
RESULTS: In this work, flower-like ZnO@Pt composites were simply synthesized at room temperature, the flower-like structure and the high electron mobility of ZnO endow ZnO@Pt with stronger peroxidase-like activity. Consequently, dual-mode (UV-vis and smartphone) colorimetric sensors were designed to detect Hg2+. In UV-vis mode, the Hg2+ concentration linear range was 10-400 nM, and the limit of detection (LOD) was 0.54 nM. In smartphone mode, the Hg2+ concentration linear range was 50-1250 nM, and the LOD was 29.8 nM. A parallel analysis in 3 real water samples was confirmed by ICP-MS, the results showed good correlations (R2 > 0.98), indicating the practical reliability of these sensors.
CONCLUSIONS: The novel flower-like ZnO@Pt composites with high stability, catalytic activity and Hg2+ response were simply synthesized at room temperature, simplifying the synthesis steps and reducing costs. The sensitivity of the developed colorimetric sensor in UV-vis mode was 3-145 times higher than that of the similar methods. The colorimetric sensor in smartphone mode broadened the detection range and improved the portability of Hg2+ detection. Thus, the dual-mode (UV-vis and smartphone) colorimetric sensors providing new detection modes for rapid monitoring of Hg2+ in environmental water.

While waters might be contaminated by oocysts from >40 Cryptosporidium species, only viable oocysts of C. parvum and C. hominis truly pose the main health risk to the immunocompetent population. Oocyst viability is also an important but often neglected risk factor in monitoring waterborne parasites. However, commonly used methods in water monitoring and surveys cannot distinguish species (microscopic observation) or oocyst viability (PCR), as dead oocysts in water could retain gross structure and DNA content for weeks to months. Here, we report new TaqMan qRT-PCR/qPCR assays for quantitative detection of viable C. parvum and C. hominis oocysts. By targeting a hypothetical protein-encoding gene cgd6_3920 that is highly expressed in oocysts and variable between species, the qRT-PCR/qPCR assays achieve excellent analytical specificity and sensitivity (limit of quantification [LOQ] = 0.25 and 1.0 oocyst/reaction). Using calibration curves, the number and ratio of viable oocysts in specimens could be calculated. Additionally, we also establish a TaqMan-18S qPCR for cost-effective screening of pan-Cryptosporidium-positive specimens (LOQ = 0.1 oocyst/reaction). The assay feasibility is validated using field water (N = 43) and soil (79) specimens from 17 locations in Changchun, China, which detects four Cryptosporidium species from seven locations, including three gp60-subtypes (i.e., IIdA19G1, IIdA17G1 and IIdA24G2) of C. parvum oocysts showing varied viability ratios. These new TaqMan q(RT)-PCR assays supplement current methods in the survey of waters and other samples (e.g., surfaces, foods and beverages), and are applicable to assessing the efficiency of oocyst deactivation protocols.

Hydrogen sulfide (H2S) is a common toxic gas that threatens the quality and safety of environmental water and food. Herein, a new near-infrared fluorescent probe DTCM was synthesized and characterized by single crystal X-ray diffraction for sensing H2S. It exhibited a remarkable \"turn-on\" near-infrared (NIR) emission response at 665 nm with a remarkably massive Stokes shift of 175 nm, super-rapid detection ability (within 30 s), excellent photostability, high selectivity and sensitivity (limit of detection, LOD = 58 nM). Additionally, the probe was successfully utilized for the detection of H2S in environmental water samples. The DTCM-loaded test papers enabled convenient and real-time monitoring of H2S produced by food spoilage.

Experimental and theoretical assessments of a graphene oxide-based polymer as adsorbent for thin film microextraction (TFME) were conducted as part of this research. Graphene oxide (GO) was embedded in the organic polymer poly(styrene-co-divinylbenzene) (PS-DVB) to prepare a sorbent suitable for direct-immersion TFME. A TFME membrane coating prepared with the GO/PS-DVB sorbent and polydimethylsiloxane (PDMS) as binder was then applied for extraction of organic pollutants from aqueous and gaseous samples. The surface morphology of the TFME coating was examined by scanning electron microscopy (SEM). Various TFME parameters influencing extraction efficiency, such as extraction time and temperature, desorption temperature, and ionic strength, were investigated and optimized. In a comparison of TFME membranes, the GO/PS-DVB/PDMS TFME membrane was shown to yield higher extraction efficiencies for the targeted analytes than the pure PDMS and DVB/PDMS TFME membranes. The calibration graphs of the organic pollutants displayed linearity for most of the target analytes within the 10-2000 ng L-1 concentration range. The repeatability (RSD %, n = 5) and reproducibility (RSD %, n = 3) of the method were in the ranges of 2.2-5.9 %, and 3.2-8.5 %, respectively, at a concentration level of 500 ng L-1, whereas accuracy (%) ranged between 79.8 and 119 %. The developed method was successfully applied for determinations of organic pollutants in tap water, lake water, and wastewater samples. Furthermore, the impact of mass transfer kinetics on extractions by the GO/PS-DVB/PDMS TFME membrane from gaseous samples was theoretically discussed and experimentally verified. The results of this work demonstrate that the GO/PS-DVB/PDMS TFME method is a simple, efficient, and environmentally friendly method for pre-treatment of organic pollutants.

Over the years, bioaccumulation of hazardous chemicals in the food chain has become a critical issue, resulting in numerous health risks. Environmental mitigation aims to clean up contaminated sites and eliminate hazardous materials from the air, water, or soil to restore the site to its original and safe condition. Pesticides constitute one of the most dangerous environmental pollutants which are generally used to increase crop production. Addressing the removal or treatment of pesticides has become pivotal in mitigating environmental threats. Diverse remediation methods are employed to protect the environment and public health. Graphene-based materials have emerged as promising candidates with exceptional properties, including excellent adsorption capacity due to their high surface area, strong hydrophilicity, and tunable properties. Owing to these properties, they have been attracting major research attention in the field of design and fabrication of materials for the mitigation of pesticides from the environment such as from contaminated food, water and other samples. Various physical, chemical and biological extraction techniques are adopted to remove pesticides. This review article provides an insight into the potential role of graphene-based materials in the environmental remediation of pesticides. We have focused on the removal of Organophosphates, Organochlorines, Carbamates and Pyrethroids present in water, fruit, vegetable and other samples, highlighting the urgent need for environmental remediation. While graphene-based materials hold potential for pesticide remediation, addressing challenges in scalable production, assessing long-term sustainability, and mitigating potential environmental impacts are critical steps for successful large-scale applications.

Here we evaluated the gill epithelial cell line ASG-10 from Atlantic salmon, as an in vitro model for research on known water quality challenges in aquaculture. Ammonia/ammonium (NH3/NH4+), a recognized challenge in water-intensive recirculating aquaculture systems (RAS), induced lysosomal vacuolization, reduced protein degradation and cell migration of the ASG-10 cells. Aluminium (Aln+), another challenge in freshwater aquaculture facilities had only minor effects. Next, we investigated the tolerance for direct water exposure of ASG-10. The cells tolerated water with osmolarity between 169 and 419 mOsmol/kg for 24 h. However, cells exposed for 3 h to water at 863 mOsmol/kg changed cellular morphology and induced gene expression related to stress (gpx1, casp3, hsp70), and after 24 h exposure cellular viability was severely reduced. Nevertheless, when the cells were grown in transwell inserts, they tolerated 863 mOsmol/kg for 3 h and induction of stress response associated genes was considerably reduced. Lastly, the ASG-10 cells were exposed to water samples, with no known quality issues, from different aquaculture facilities. The cells showed no differences in viability or morphology compared to their representative control. In conclusion, the ASG-10 cell line is a promising in vitro model to study water quality challenges and whole water samples.

A reliable, rapid, and low-cost procedure for determining very low concentrations of hexavalent chromium (Cr) in water is discussed. The procedure is based in the classical reaction of Cr6+ with diphenylcarbazide. Once this reaction has taken place, sodium dodecylsulfate is added to obtain an ion-pair, and Triton X-114 is incorporated. Next, the heating of the mixture allows two phases that can be separated by centrifugation to be obtained in a cloud point microextraction (CPE) process. The coacervate contains all the Cr6+ originally present in the water sample, so that the measurement by molecular absorption spectrophotometry allows the concentration of the metal to be calculated. No harmful organic solvents are required. The discrimination of hexavalent and trivalent forms is achieved by including an oxidation stage with Ce4+. To take full advantage of the pre-concentration effect inherent to the coacervation process, as well as to minimize reagent consumption and waste generation, a portable mini-spectrophotometer which is compatible with microvolumes of liquid samples is used. The preconcentration factor is 415 and a chromium concentration as low as 0.02 µg L-1 can be detected. The procedure shows a good reproducibility (relative standard deviation close to 3%).

In this work, Cassia tora (C. tora) have been used as a template to synthesize green fluorescent C. tora molybdenum nanoclusters (C. tora-MoNCs) through a green chemistry approach. These C. tora-MoNCs showed a quantum yield (QY) of 7.72% and exhibited a significant emission peak at 498 nm when excited at 380 nm. The as-prepared C. tora-MoNCs had an average size of 3.48 ± 0.80 nm and showed different surface functionality. The as-synthesized C. tora-MoNCs were successfully identified the hydroxyl radical (•OH) via a fluorescence quenching mechanism. Also, fluorescence lifetime and Stern-Volmer proved that after the addition of •OH radicals it was quenched the fluorescence intensity via a static quenching mechanism. The limit of detection is 9.13 nM, and this approach was successfully utilized for sensing •OH radicals in water samples with a good recovery rate.

BACKGROUND: Herein, a new extraction procedure based on in-situ formation of carbon dioxide-incorporated solid sorbent was introduced for dispersive solid phase extraction of phenolic compounds from aqueous samples. In this study, incorporation of carbon dioxide into the structure of a diamine led to the formation of a solid compound in the sample solution that adsorbed the analytes.
RESULTS: The sample solution was mixed with isophorone diamine and placed under carbon dioxide stream. By doing so, isophorone diamine reacted with carbon dioxide and produced a carbamic acid analogue. It was dispersed into the sample solution as tiny particles that adsorbed the analytes. The adsorbed analytes were eluted by a volatile organic solvent and concentrated more by the vaporization of the eluate. The extraction procedure was done at low temperature to limit the releasing carbon dioxide from the produced compound. To obtain the reliable results, the method was validated and the obtained limits of detection and quantification were in the ranges of 0.29-41 and 0.96-1.3 ng/mL, respectively. Acceptable relative standard deviation (≤7.3%) and coefficient of determination (≥0.994) values confirmed the method repeatability and linearity. High enrichment factors (410-435) and extraction recoveries (82-87%) were attained with the introduced method.
UNASSIGNED: In this work, a chemical reaction was done between isophorone diamine and carbon dioxide in solution. The produced product (sorbent) was insoluble in solution and dispersed in whole parts of the solution as tiny particles. A high contact area between the sorbent and analytes provided high extraction efficiency for the analytes. The method was successful utilized in determining target analytes in real samples and the matrix effect of the samples had no important effect on the obtained results.