Application of a new focused microwave technology with species-specific isotope dilution analysis for the quantitative extraction of organometallic contaminants in solid environmental matrices

A new self-tuning single-mode-focused microwave technology has been evaluated in this work to perform the quantitative routine extraction of organometallic species from solid matrices of environmental interest. Species-specific isotope dilution analysis has been employed to better investigate the real influence of the microwave-assisted extractions on the final results. The advantages of such methodology in comparison with other established microwave units for the routine speciation analysis of organomercury and organotin compounds are discussed (such as the capability of using disposable glass vials, a self-tuning mode to provide an accurate control of the temperature and pressure inside of the vials, and the possibility of performing automated sequence of extractions with low sample size). The results obtained in this work demonstrated that such technology provides a fast and reliable quantitative extraction of the organometallic species in a wide range of extraction conditions even when the multi-elemental (Sn and Hg) species-specific determination is carried out.     

Molecularly imprinted nanoparticles-based electrochemical sensor for determination of ultratrace parathion in real samples

Molecularly imprinted polymer nanoparticles (nano-MIP), containing parathion selective sites, were synthesized by using suspension polymerization in silicon oil and then used for carbon paste electrode preparation. The obtained electrode was applied as an electrochemical sensor for parathion determination in different fruit and vegetable samples. Different factors including electrode composition, conditions of parathion extraction in the electrode and electrochemical measurement conditions were evaluated and then optimized by using various techniques of screening and response surface experimental designs. Electrode response to parathion (Res₁) and its selectivity for parathion (Res₂) were the desired responses. These responses were optimized simultaneously. After optimization, a sensor with high selectivity and picomolar detection limit were obtained. It was shown that the sensor response to parathion concentration was linear in the concentration range of 0.05 to 150?nmol?L^?1. The detection limit of designed sensor was calculated equal to 0.02?nmol?L^?1. The developed determination method was properly used for ultra-trace level assay of parathion in different fruit and cabbage samples.     

The synthesis of luminescent lanthanide-based chemosensors for the detection of zinc ions

Herein, we report the synthesis of two lanthanide-based chemosensors, Tb-5 and Eu-6, designed to sense free zinc ions (Zn²⁺) in aqueous solutions. The Tb-5 complex features a bis(2-pyridinylmethyl)amine moiety as a zinc(II)-responsive lanthanide-sensitising ‘antenna’, while Eu-6 incorporates a quinoline-based moiety for this purpose. Luminescence enhancements of 210% and 340% are observed upon addition of Zn²⁺ ions to Tb-5 and Eu-6, respectively. Both sensors are selective for Zn²⁺ ions over several other cations of environmental significance.     

Determination of four sulfonylurea herbicides in tea by matrix solid‐phase dispersion cleanup followed by dispersive liquid–liquid microextraction

Matrix solid‐phase dispersion combined with dispersive liquid–liquid microextraction has been developed as a new sample pretreatment method for the determination of four sulfonylurea herbicides (chlorsulfuron, bensulfuron‐methyl, chlorimuron‐ethyl, and pyrazosulfuron) in tea by high‐performance liquid chromatography with diode array detection. The extraction and cleanup by matrix solid‐phase dispersion was carried out by using CN‐silica as dispersant and carbon nanotubes as cleanup sorbent eluted with acidified dichloromethane. The eluent of matrix solid‐phase dispersion was evaporated and redissolved in 0.5 mL methanol, and used as the dispersive solvent of the following dispersive liquid–liquid microextraction procedure for further purification and enrichment of the target analytes before high‐performance liquid chromatography analysis. Under the optimum conditions, the method yielded a linear calibration curve in the concentration range from 5.0 to 10 000 ng/g for target analytes with a correlation coefficients (r²) ranging from 0.9959 to 0.9998. The limits of detection for the analytes were in the range of 1.31–2.81 ng/g. Recoveries of the four sulfonylurea herbicides at two fortification levels were between 72.8 and 110.6% with relative standard deviations lower than 6.95%. The method was successfully applied to the analysis of four sulfonylurea herbicides in several tea samples.     

Novel modified carbon nanotubes as a selective sorbent for preconcentration and determination of trace copper ions in fruit samples

In this work, multiwalled carbon nanotubes were reacted with N‐[3‐(triet‐hoxysilyl)propyl]isonicotinamide to prepare pyridine‐functionalized carbon nanotubes. This novel sorbent was characterized by infrared spectroscopy, thermal and elemental analysis, and scanning electron microscopy. Functionalized carbon nanotubes were applied for the preconcentration and determination of copper ions using flame atomic absorption spectrometry. Various parameters such as sample pH, flow rate, eluent type and concentration, and its volume were optimized. Under optimal experimental conditions, the limit of detection, the relative standard deviation, and the recovery of the method were 0.65 ng/mL, 3.2% and 99.4%, respectively. After validating the method using standard reference materials, the new sorbent was applied for the extraction and determination of trace copper(II) ions in fruit samples.     

TiO2 nanotube arrays prepared by anodization as an adsorbent in micro‐solid‐phase extraction to preconcentrate and determine nitrogen‐containing polycyclic aromatic hydrocarbons in water samples

In this study, a simultaneous determination method for nitrogen‐containing polycyclic aromatic hydrocarbons including 7‐methylquinoline, acridine, 5,6‐benzoquinoline, carbazole, and 9‐methylcarbazole was developed. This method is based on a micro‐solid phase extraction using TiO₂ nanotube arrays as an adsorbent in combination with HPLC. Some factors that had an effect on the enrichment were optimized, such as sample pH, surfactant concentration, ion strength, type of eluent, equilibrium time, and desorption time. Under the optimized conditions, the linear ranges and LODs were in the range of 0.01–100 and 0.0035–0.81 μg/L, respectively. The precisions of the proposed method were <9.51% (RSD, n = 6). The developed method was validated with four real samples, and the spiked recoveries were in the range of 77–109.6%. All these results demonstrated that this novel micro‐solid‐phase extraction technique was a reliable alternative to conventional preconcentration method for the extraction and analysis of such nitrogen‐containing polycyclic aromatic hydrocarbons in complex samples.     

Molecularly imprinted spin column extraction coupled with high‐performance liquid chromatography for the selective and simple determination of trace nitrophenols in water samples

In this study, we developed a simple and selective spin column extraction technology utilizing hydrophilic molecularly imprinted polymers as the sorbents for extracting nitrophenol pollutants in water samples (the East Lake, the Yangtze River, and wastewater). The whole procedure was achieved by centrifugation of the spin column, and multiple samples were simultaneously processed with a low volume of solvent and without evaporation. Under the optimized condition, recoveries of nitrophenol compounds on the spin column packed with hydrophilic molecularly imprinted polymers ranged from 87.3 to 92.9% and an excellent purification effect was obtained. Compared with activated carbon, multi‐walled carbon nanotubes, LC‐C₁₈ sorbents, hydrophilic molecularly imprinted polymers exhibited a highly selective recognition ability for nitrophenol compounds and satisfactory sample extraction efficiency. Subsequently, the spin column extraction coupled with high‐performance liquid chromatography was established, which was found to be linear in the range of 2–1000 ng/mL for 2,4‐dinitropehnol and 2‐nitrophenol, and 6–1000 ng/mL for 4‐nitrophenol with correlation coefficients greater than 0.998. The detection limits ranged from 0.3–0.5 ng/mL. It is shown that the proposed method can be used for the determination of trace nitrophenol pollutants in complex samples, which is not only beneficial for water quality analysis but also for environmental risk assessment.     

A new Approach for the Voltammetric Sensing of the Phytoestrogen Genistein at a Non-modified Boron-doped Diamond Electrode

An effective electrochemical sensor was constructed using an unmodified boron-doped diamond electrode for determination of genistein by square-wave voltammetry. Cyclic voltammetric investigations of genistein with HClO₄ solution indicated that irreversible behavior, adsorption-controlled and well-defined two oxidation peaks at about +0.92 (P_A1) & +1.27 V (P_A2). pH, as well as supporting electrolytes, are important in genistein oxidations. Quantification analyses of genistein were conducted using its two oxidation peaks. Using optimized experiments as well as instrumental conditions, the current response with genistein was proportionately linear in the concentrations range of 0.1 to 50.0 μg mL⁻¹ (3.7×10⁻⁷−1.9×10⁻⁴ mol L⁻¹), by the detection limit of 0.023 μg mL⁻¹ (8.5×10⁻⁸ mol L⁻¹) for P_A1 and 0.028 μg mL⁻¹ (1.1×10⁻⁷ mol L⁻¹) for P_A2 in 0.1 mol L⁻¹ HClO₄ solution (in the open circuit condition at 30 s accumulation time). Ultimately, the developed method was effectively applied to detect genistein in model human urine samples by using its second oxidation peak (P_A2).     

New method of identifying morphine in urine samples using nanoparticle-dendrimer-enzyme hybrid system

The incorporation of morphine (MOR) into the nanoparticle structure is a viable alternative to traditional enzyme usage. It has good biological potential to separate MOR from real urine samples. In this study, a new method of MOR identification in real urine samples was synthesized using the β-glucuronidase-dendrimer poly amidoamine (PAMAM) enzyme hybrid system. Replacing MOR in dendrimer cavities significantly reduces enzyme consumption. The replacement technique is done in dendrimer cavities in two stages as an alternative to β-glucuronidase enzyme and even MOR. In this paper, firstly, PAMAM dendrimer G2 was synthesized based on silica. The β-glucuronidase enzyme was replaced inside its dendrimer cavities and the compound was released into a real urine sample containing MOR. The enzyme was extracted from dendrimer cavities. The MOR- β-glucuronidase enzyme bond broke. In the next stage of the process, free MOR entered the PAMAM dendrimer G2 cavities. MOR was detected in real urine samples.     

Recent advances in analytical methodologies based on mass spectrometry for the environmental analysis of halogenated organic contaminants

Halogenated organic contaminants, including legislated and potential persistent organic pollutants and their precursors, represent a major environmental concern due to their hazardous effects in humans and wildlife as well as their ability to bioaccumulate through the food chain, their high resistance to environmental degradation, and their long-range atmospheric transport potential. The monitoring of these compounds in the environment at ultra-trace concentration levels requires highly selective and sensitive analytical methodologies. The lack of reference step-by-step methods led to a high number of reliable determinations depending on analytes, the complexity of the sample, and available instrumentation. Thus, this review article is mainly focused on the last advances in the analytical methodologies for the determination of halogenated organic contaminants. Methodologies regarding sample treatment, chromatographic separation, and mass spectrometry analysis have been reviewed to finally highlight the future perspectives for the improvement of the analytical determinations of these compounds and the throughput of environmental control laboratories in this field.