SPA enhanced FPIA‐based detection of pesticide residue with ppb/ppt level detection limit

Pesticide residue in fruits & vegetables is one of the key issues affecting the export of rural products in India. Pesticide exposure or intake causes major nervous system problems in children. The solutions to quantitate them in field are rare and the pesticide residue detection in the parts per billion (ppb) ranges is challenging. Except ELISA, none of the existing methods can detect pesticide residues in ppb range in the field. We employed a new approach of concentrating field samples and used sodium polyacrylate (SPA) as water absorbing material. The SPA beads concentrate the field samples and obtained a sub ppb range detection using an existing FPIA system and could improve overall sensitivity by 10‐100 fold. The developed assay can be done in few seconds. We have used three pesticides 2,4‐D, atrazine and methyl parathion with 0.1, 0.5 and 3 ppb detection limit respectively. We developed a simple field ready FPIA device and used sodium poly acrylate (SPA) in this biochemical FPIA to enhance sensitivity. Our tests with spiked field samples offers a possibility of using SPA concentration assisted FPIA in field. This study will have far reaching applications of both qualitative & quantitative analysis chemical analytes in field samples.Inspec keywords: agrochemicals, organic compounds, enzymesOther keywords: SPA enhanced FPIA‐based detection, ppb‐level detection limit, rural product export, India, pesticide exposure, Pesticide intake, nervous system problems, pesticide residue detection, parts‐per billion ranges, enzyme‐linked immunosorbent assay, ELISA, sodium polyacrylate, water absorbing material, SPA beads, fluorescence polarisation immunoassay system, overall sensitivity improvement, antigen‐antibody pairs, 2,4‐dichlorophenoxyacetic acid, atrazine, methyl parathion, biochemical FPIA, interstitial spaces, bulk medium, qualitative analysis, quantitative analysis, ppt‐level detection limit     

Rational design of smart adsorbent equipped with a sensitive indicator via ligand exchange: A hierarchical porous mixed-ligand MOF for simultaneous removal and detection of Hg2+

The increasing accumulation of toxic mercury species in water environment has posed a serious health threat worldwide, making it inevitable to develop the versatile materials to achieve efficient prevention and remediation of mercury pollution. Guided by the solvent-assisted ligand exchange (SALE) approach, this work rationally constructed a mixed-ligand NH2-UiO-66-SH (NSU66) with hierarchical-pore structure by incorporating the thiol-rich ligands (H2DMBD) into the water-stable NH2-UiO-66 (NU66) precursor to act as a smart adsorbent equipped with sensitive detector for simultaneous sensing and removal of Hg2+. Unlike the traditional adsorbents, the as-prepared NSU66 not only exhibits a remarkable removal ability with fast capture rate (within 60.0 min), large uptake capacity (265.29 mg/g), and qualified selectivity, but also possesses satisfactory sensing capability, accompanied by low detection limit (3.50 × 10?2 μM), wide linear range (1.00–99.7 μM), high specificity, and strong anti-interference capability. The detection function plays a vital role in indicating the removal behavior and the pre-enrichment effect of adsorption process correspondingly improves the sensitivity of indicator. Notably, the sensing and trapping capabilities of NSU66 are significantly improved compared to the NU66, which stems from the delicate design of the mixed-ligand and hierarchical-pore structure. Furthermore, proven excellent stability and recyclability emphasize the feasibility of NSU66 in practical applications. These results suggest that the smart NSU66 adsorbent can serve as a favorable platform for early warning and guided removal of toxic Hg2+ in water.     

Determination of trace levels of anionic surfactants in river water and wastewater by a flow injection analysis system with on-line preconcentration and potentiometric detection

The authors present an automated flow injection analysis (FIA) system for the determination of low levels of anionic surfactants in river water and wastewater. The system uses especially constructed tubular flow-through ion-selective electrodes (ISEs) as potentiometric sensors and on-line preconcentration techniques. The anionic surfactant ISEs employed are of the all-solid-state type with a plasticized PVC membrane. They show a general response to anionic surfactants with a lower limit of linear response of ～10(-)(5) M, when used in direct determinations. However, their specificity is limited, which hampers their direct use with environmental samples. Therefore, the FIA system presented here includes a solid-phase extraction procedure for purification and preconcentration of analytes. Breakthrough curves were constructed to characterize different sorbents and different eluents were tested to optimize the preconcentration process. The FIA system was first applied to the determination of different types of anionic surfactant standards. Potentially interfering substances such as chloride, nitrate, and nonionic surfactants were checked to verify that they did not interfere on the response of the system. Concentrations of ～10(-)(7) M (0.03 ppm) of sodium dodecyl sulfate could be detected in the nonlinear response region when 3 mL of sample was preconcentrated and eluted with 50 μL of a 75% acetonitrile/water (v/v) solution. Precision was 2% RSD (n = 31) for a 1 × 10(-)(6) M sodium dodecyl sulfate standard solution and the sample throughput was 10 h(-)(1). The FIA system was then used for the determination of total anionic surfactants in river water and wastewater.     

Determination of dosimetric characteristics of a new design 125I brachytherapy source with an Ag + Al2O3 marker using the Monte Carlo code MCNPX

The dosimetric parameters of a new ¹²⁵I brachytherapy seed model were determined by Monte Carlo simulations according to the TG-43U1 recommendation using MCNPX v.2.6 code. The source contains a cylindrical Ag + Al₂O₃ marker located in the center of the seed, onto which a thin layer of ¹²⁵I has been uniformly adsorbed. The dose rate constant of 0.980 ± 1.2% cGy h^?1 U^?1 in liquid water was obtained. Acceptable agreement between the calculated dosimetric parameters of this new source and other commercial source models indicates that this seed is acceptable for clinical use.     

Determination of intracellular species at the level of a single erythrocyte via capillary electrophoresis with direct and indirect fluorescence detection.

Intracellular contents reflect the specific history of a cell including innate physiological heterogeneity as well as differing levels of exposure to environmental influences. A method capable of analyzing a variety of species from within a single human erythrocyte is demonstrated. Guided by a microscope, individual cells can be drawn into open capillaries of 10-microns i.d. On contact with a low ionic strength buffer solution, the cell lyses and releases its intracellular fluid. The ionic components are then separated by capillary electrophoresis. For glutathione, microderivatization with a fluorescent reagent can be accomplished in vitro with monobromobimane. The effects of extracellular oxidizing and reducing agents on the glutathione levels can thus be followed. For sodium and potassium, or any other ionic species, charge displacement of a fluorescent cation results in indirect fluorescence detection. The two detection modes are suitable for intracellular components present at low-attomole and sub-femtomole levels, respectively.     

A voltammetric sensor for the detection of 2-aminophenol in the presence of bisphenol A using a carbon paste electrode modified with N-doped reduced graphene oxide/CuO nanocomposite and ionic liquid

Journal of Materials Science: Materials in Electronics - In present work, a novel and facile electrode was constructed using the modification of carbon paste electrode (CPE) with N-doped reduced...