Real Sample Matrix Research Articles

Determination of trace levels of thiazopyr residues in oolong tea samples using metal sieve-linked double syringe based liquid-phase microextraction coupled with gas chromatography-mass spectrometry

Thiazopyr has raised concerns about its potential impact on human health. Hence, detection of trace levels of thiazopyr herbicide has become critically important. This study presents a highly precise and accurate method to determine thiazopyr at trace levels using a combination of metal sieve-linked double syringe based liquid-phase microextraction (MSLDS-LPME) and Gas Chromatography-Mass Spectrometry (GC-MS) system. A thorough optimization of all parameters affecting the method's efficiency was performed using a univariate optimization approach, followed by an evaluation of the system's analytical performance. Employing the developed method in conjunction with the MSLDS-LPME-GC-MS system yielded a limit of detection (LOD) of 2.73 µg/kg and a limit of quantification (LOQ) of 9.11 µg/kg. To assess the method's applicability, a recovery study was conducted using oolong tea as a real sample matrix, employing a matrix-matching calibration approach. The results of recovery studies demonstrated acceptable recoveries ranging from 87.5 % to 101.9 %.

3D Plasmonic Gold Nanopocket Structure for SERS Machine Learning‐Based Microplastic Detection

AbstractMicroplastics (MPs) are present not only in the environment but also in drinking water, food, and consumer products. These MPs being toxic, carcinogenic, endocrine disrupting, and genetic risk creators cause several diseases. Despite various approaches, the development of onsite applicable, facile, and quick MP detection methods is still challenging. Here, 3D‐plasmonic gold nanopocket (3D‐PGNP) nanoarchitecture is formed on a paper substrate for simultaneous MP filtration and detection. The paper‐based 3D‐PGNP is integrated with a syringe filter device, and then, MP‐containing solutions are injected through the syringe. Subsequent detection of the MPs using the surface‐enhanced Raman scattering (SERS) successfully identifies the MPs without pretreatment. The interface and volumetric hotspot generation of 3D‐PGNP around the captured MPs significantly improves the sensitivity, which is confirmed by finite‐difference time‐domain simulation. Then, the SERS mapping images obtained from a portable Raman spectrometer are transformed into digital signals via machine learning (ML) technique to identify and quantify the MP distribution. The developed SERS‐ML‐based MP detection method is applied for mixture MPs and for real matrix samples, demonstrating that the method provides improved accuracy. This system is expected to be used for various MPs detection and for environmentally hazardous substances, such as bacteria, viruses, and fungi.

Quantification of trace fenuron in waste water samples by matrix matching calibration strategy and gas chromatography-mass spectrometry after simultaneous derivatization and preconcentration.

This study presents a highly sensitive and accurate analytical strategy for the determination of fenuron in wastewater samples using gas chromatography-mass spectrometry (GC-MS). Simultaneous derivatization and spray-based fine droplet formation-liquid phase microextraction (SFDF-LPME) method was developed and performed to achieve low detection limits. The parameters of the derivatization and SFDF-LPME method were optimized by univariate approach to improve sensitivity and selectivity. Under the optimum SFDF-LPME-GC-MS conditions, the limit of detection (LOD) and limit of quantitation (LOQ) were found to be 0.15 and 0.49 mg/kg, respectively. In addition, the linear range was calculated as 0.51-24.50 mg/kg. Recovery studies were carried out on wastewater samples to determine the accuracy of the developed method and its applicability to real sample matrix. Matrix matching calibration strategy was applied to eliminate/reduce any possible interference effects caused by the complexity of the wastewater matrix and to increase the accuracy of the analytical results. Percent recovery results varied between 85.9 and 120.9% with small percent relative standard deviation values. These results were satisfactory in terms of the accuracy and applicability of the proposed method for wastewater samples.

Hierarchical porous zeolitic imidazolate framework‑8 supported hollow-fiber liquid-phase microextraction of nine typical phenolic pollutants in water samples followed by electrophoretic analysis

Hierarchical porous zeolitic imidazolate framework‑8 (HpZIF-8) have not only good chemical and thermal stability, but also pore structures of different sizes. In this work, HpZIF-8 supported hollow-fiber liquid-phase microextraction (HpZIF-8@HF-LPME) co-modified with tributyl phosphate and 2-nitroethyl benzene was firstly developed for purification and enrichment of nine typical phenolic pollutants followed by electrophoretic separation and amperometric detection (CE-AD). The key enrichment parameters were optimized by full factorial experimental and central composite designs. Under the optimum conditions, the maximum enrichment factors for the nine analytes were 479 (phenol), 249 (2-chlorophenol), 821 (4-chlorophenol), 1253 (3-methylphenol), 1376 (2,4-dichlorophenol), 1078 (2,4,6-trichlorophenol), 200 (pentachlorophenol), 614 (4-nitrophenol) and1827 times (bisphenol A), respectively. The limits of detection were 0.060-1.5µg L-1 (S/N=3) in real sample matrixes. This proposed method has been successfully applied to water samples with high ionic strength, and the average recoveries were in the range of 80.2-118.0%. This developed method of HpZIF-8@HF-LPME/CE-AD needs no desorption and derivatization, providing an alternative for monitoring typical phenolic pollutants in water samples.

Self-checking dual-modal aptasensor based on hybrid Z-scheme heterostructure of Zn-defective CdS/ZnS for oxytetracycline detection

Electrochemical detection methods have been widely used for trace target detection with satisfactory results. However, most of the existing electrochemical sensors rely only on single signal output, which inevitably suffer from the interference of the complex matrix of real samples. Herein, we proposed a dual-modal aptasensor for oxytetracycline assay with self-checking function by integrating photoelectrochemical (PEC) and electrochemical (EC) signal outputs in one analysis system. Zn-defective CdS/ZnS heterostructure was synthesized and served as the photo-electroactive substrate for constructing the biorecognition process, while methylene blue (MB) was used as a dual-functional probe to enhance both PEC and EC signals. Due to the high activity of Zn-defective CdS/ZnS heterojunction and the unique dual-modal signal readout strategy, the biosensing platform exhibits superior analytical performance with the relatively wide linear range (0.01–50 ng mL−1), lower detection limits of 1.86 pg mL−1 (PEC mode) and 3.08 pg mL−1 (EC mode), as well as good selectivity, stability and reproducibility. The proposed dual-model analytical system with self-checking function is envisioned to provide a new approach for sensitive and reliable biosensing.

Electrochemically synthesized green fluorescent carbon dots for quantitation of hypochlorite and carbendazim.

Green emission carbon dots (CDs) electrochemically prepared from 2,6-pyridinedicarboxylic acid and o-phenyl-enediamine were applied separately for the quantitation of hypochlorite and carbendazim. The characteristic and optical properties of the CDs were studied through fluorescence, UV-vis absorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. The synthesized CDs were mainly 0.8-2.2 nm in size, with an average size of 1.5 nm. The CDs exhibited green luminescence centered at 520 nm when excited by 420 nm light. The green emission of the CDs is quenched after the addition of hypochlorite, mainly through the redox reaction between hypochlorite and hydroxyl groups on the CDs surface. Furthermore, the hypochlorite-induced fluorescence quenched can be prevented in the presence of carbendazim. The sensing approaches exhibit good linear ranges of 1-50 μM and 0.05-5 μM for hypochlorite and carbendazim, respectively, with low detection limits of 0.096 and 0.005 μM, respectively. Practicalities of the luminescent probes were separately validated by the quantitation of the two analytes in real sample matrix with recoveries ranging from 96.3 to 108.9% and the relative standard deviation values below 5.51%. Our results show the potential of the sensitive, selective, and simple CD probe for water and food quality control.

Zr-MOF-Induced Smart Accumulation Enables Surface-Enhanced Raman Spectroscopic Detection of Dioxin at ppt Level in Food Samples.

The fast and economical detection of trace polychlorinated dibenzo-p-dioxins (PCDDs) in food samples by current mass spectrum-based methods is hindered by tedious sample preparation and bulky & expensive analytical instruments. Surface-enhanced Raman spectroscopy (SERS) successfully detects many organic pollutants in foods but not dioxins because the employed metal nanoparticles weakly adsorb hydrophobic PCDDs. Herein, we report the detection of PCDDs in milk with SERS for the first time using a bifunctional substrate consisting of Au nanoparticles embedded in a zirconium-based metal-organic framework shell (AuNP/Zr-MOF). 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), as the most toxic PCDD, is detected as low as 1.2 parts per trillion (ppt) in real milk samples with massive interfering substances in 30 min, which is the lowest among all reported methods. The aromatic rings of Zr-MOF promote the smart accumulation of TCDD through π-π interactions, and Au-Cl interactions drive TCDD onto Au surfaces. Zr-MOF shells with pore sizes of 12.7 and 20 Å block the accessibility of larger interfering molecules. A one-step apparatus and protocol are established to be superior to traditional methods in terms of time and cost. This work provides new insight into a rational screening method for the detection of persistent organic pollutants in a real sample matrix.

How safe is our food we eat? An electrochemical lab-on-kitchen approach towards combinatorial testing for pesticides and GMOs; A case study with edamame

In our daily life, as consumers we are constantly made aware of the impact of pesticides and other modifications to food products derived from genetically modified organisms (GMO’s) that have an impact on human health. In our connected world, there is an immense interest for on-demand information about food quality prior to consumption. The gold standard method to detect pesticides or GMOs residues in food is complex and is not amenable to rapid consumer use. In this study, we demonstrate the feasibility of an electrochemical portable sensing approach for the simultaneous direct detection of spiked pesticides chlorpyrifos (Chlp) and GMOs protein Cry1Ab in real edamame soy matrix. The immunoassay based two-plex sensing platform was fabricated using respective antibody’s Chlp on one side and Cry1Ab on other side. A simple lab-on-kitchen level preparation of matrix has been demonstrated and sensor response was tested using non-faradaic electrochemical impedance spectroscopy (EIS), which showed a linear response in Cry1Ab/Chlp concentrations from 0.3 ng/mL to 243 ng/mL with limit of detection 0.3 ng /mL for both the target antigens (Cry1Ab and Chlp) respectively. The spiked and recovery test results fall within ± 20% error in real sample matrix which demonstrates the performance of the our platform with maximum residue limit (MRL) for the given targets. Such electrochemical portable multi-analyte direct sensing tool with simple matrix processing protocol can be a future commercial field-testing tool for use at everyday consumer level.

Soya bean derived activated carbon as an efficient adsorbent for capture of valuable heavy metals from waste aqueous solution

Abstract The removal of hazardous metal ions from liquid waste effluents is very important for water as well as environmental safety. In this regard, this article discusses in detail the U(VI) uptake from aquatic environment using biomass-based Soya Bean activated carbon (labeled as AC-SB). XRD, SEM, FTIR, Raman, and BET analysis were used to characterize the synthesized AC-SB sorbent. Batch-type experiments were used to investigate the effect of various parameters on adsorption efficiency, including pH, metal-ion concentration, temperature, and contact time. The sorption experimental data have been described well with pseudo-second-order kinetic mathematical equations. The equilibrium state of the uptake reaction was 120 min. The Langmuir isotherm model accurately described the equilibrium process which declares that the uranium sorption is a monolayer and homogeneous process. The sorption capacity of the prepared AC was 32.7 mg g−1. Thermodynamic analysis explore that the U(VI) uptake process is endothermic, feasible and spontenous process. The displayed results demonstrate that the prepared AC-SB sorbent could be used as the proper material for uranium sorption from real matrix samples.

Tetraphenylporphyrin Decorated Bi2MoO6 Nanocomposite: Its Twin Affinity of Oxygen Reduction Reaction and Electrochemical Detection of 4-Nitrophenol.

A selective electrode for oxygen reduction reaction (ORR) and electrocatalytic reduction of 4-nitrophenol (p-NP) was fabricated on a glassy carbon electrode using organic-inorganic Bi2MoO6/H2TPP nanocomposites with different weight percentages of tetraphenylporphyrin, synthesized by the solvothermal process. Materials thus synthesized were characterized through UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analysis. The electrocatalytic performance of the modified electrode toward ORR in the 0.1 M KOH solution, the onset potential Eonset (0.942 V), E1/2 (0.704 V) vs RHE, Jd (-5.545 mA cm-2), and n = 4 physicochemical parameters were well appreciable. It exhibits good catalytic activity toward ORR through a four-electron pathway with excellent stability and high active site density, and thus, the in situ Porphy-decorated metal oxide system facilitates the electron transport process. High selectivity and efficacy for the oxygen reduction reaction (ORR) are a significant measure for several energy-converting applications. The decorated electrode, glassy carbon electrode (GCE)/Bi2MoO6/3 wt % Porphy, serves as an electrochemical sensor that exhibited good sensitivity (0.4683 μAμM-1 cm-2), good reproducibility, a low detection limit (0.0940 μM), and long-term stability in the aqueous phase without any appreciable effect in the presence of some common organic and inorganic interferences for the detection of p-NP in a linear concentration range of 0.5-350 μM. Therefore, the material performs as an effective electrode for both the ORR and the electrocatalytic reduction of p-NP with real matrix samples at room conditions.

Electrochemical Sensing Platform for the Detection of Pesticides and GMO Protein in Food Matrices

The growing technology and development in the agriculture industry has led to the introduction of genetically modified organisms (GMO’s) crops having which have high resistance to insecticides, thus there is a tremendous rise in the use of the pesticides/insecticide worldwide. The underlying concern is about the possible health issue related to their residues in the daily dietary intake viz sources such as water, fruits, vegetables and grains. Therefore, various regulatory bodies have set the maximum residue limits for safe use of these pesticides or insecticides in agriculture land. Secondly, regardless of the rising debate or controversies about the GMO’s among society and producer, their cultivation is constantly increasing. As the impact of cultivating these crops on human health are under study, more than 50 countries have mandated the labelling of these GMO’s proteins to ensure the right to information to the consumers. Although these pesticides/insecticides and GMO’s can be detected precisely using gold standard analytical methods in the food matrix, but these methods require an expert to handle, and stringent sample pre-processing steps. Thus, there is a high demand for the portable, on-field device which can be used at the consumer levels requiring no pre-sample processing steps. In our work, we explore the use of the electrochemical assay method to detect the pesticides such as Chlorpyrifos, Glyphosate and GMO proteins in high fat and low-fat food matrices. The assay-based electrochemical multiplex sensor has been developed by modifying the screen-printed Au-electrode/carbon electrode substrate with the respective antibody at optimized concentrations. The real low-fat and high-fat sample matrices has been prepared by simply blending the mix using home blender. The real sample matrix spiked with the pesticides /GMO protein were tested for calibrated dose response from 0.3 ng/mL- 243 ng/mL, and the limit of detection of less than < 10 ng/mL were observed using this developed electrochemical portable device method. Such portable electrochemical device approach could be a promising on-field sensing tool for the pesticide and GMO protein detection. Figure 1

Simultaneous detection of Cd2+ and Pb2+ by differential pulse anodic stripping voltammetry: Use of highly efficient novel Ag0(NPs) decorated silane grafted bentonite material

• Novel nanocomposite materials were synthesized adopting greener route. • Nanocomposite materials were employed for highly efficient and selective simultaneous detection of Cd 2+ and Pb 2+. • Sensing platform is unaffected with existing co-ions. • High recovery was obtained using real matrix analysis for Pb 2+ and Cd 2+. Novel and highly efficient nanomaterials were synthesized using relatively greener routes, and these materials were utilized in the trace and simultaneous detection of Cd 2+ and Pb 2+ in aqueous solutions. Silver nanoparticles (AgNP) were synthesized by using the Persea Americana leaf extract, and the AgNP were in situ decorated with the silane grafted bentonite (AgNP@Bt/TC). The structure/morphology of the synthesized materials was characterized by scanning electron microscopy/energy-dispersive X-ray (SEM/EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Nanomaterial was utilized to modify the glassy carbon electrode surface. For the first time, the fabricated electrode was employed for the single and simultaneous trace detection of lead and cadmium in aqueous solutions using the differential pulse anodic stripping voltammetry (DPASV). Extensive parametric studies viz. , pH, depositional potential, time, and potentially interfering ions were studied. Fairly good calibration lines were obtained to detect these two ions with a detection limit (LOD) of 0.79 µg/L for Cd 2 + and 0.88 µg/L for Pb 2+ . The detection method was utilized in the simultaneous detection of the metal ions in real matrix samples, which gave the recovery of 93 to 108% for cadmium and 99 to 113% for lead detection.

Simultaneous electrochemical determination of morphine and methadone by using CMK-5 mesoporous carbon and multivariate calibration

For the first time, a sensitive electrochemical sensor using a glassy carbon electrode modified with CMK-5 Ordered mesoporous carbon was fabricated for simultaneous analysis of morphine and methadone. Modern electrochemical FFT-SWV techniques and partial least-squares as a multivariable analysis were used in this method. CMK-5 nanostructures were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and Raman spectroscopy. Variables such as accumulation time and pH for the proposed sensor were optimized before quantitative analysis. To train the proposed sensor, standard mixtures of morphine (MOR), and methadone (MET) were prepared in the established linear ranges of the analyzes. The results obtained from training samples were used for PLS modeling. The efficiency of the model was determined using test and real matrix samples. The root mean square error of prediction and the squared correlation coefficients (R2p) for MET and MOR were estimated to be 0.00772 and 0.00892 and 0.948 to 0.990, respectively. The recoveries in urine samples were reported to be 97.0 and 105.6% for both MOR and MET, respectively.

Using the extract of pomegranate peel as a natural indicator for colorimetric detection and simultaneous determination of Fe3+ and Fe2+ by partial least squares–artificial neural network

AbstractA simple, novel, biocompatible, and sensitive spectrophotometric method was developed for colorimetric detection and speciation of Fe3+ and Fe2+ ions. The method is based on the complex formation of Fe3+ and Fe2+ with organic constituents containing functional groups in pomegranate peel extract (PG). Developing of the color is specifically established in the presence of Fe3+ and Fe2+. Accordingly, in addition to direct detection of both cations, we carried out a quantitative multivariate model for their accurate determination in real matrix aqueous samples. Due to spectral interference, the simultaneous determination of Fe3+ and Fe2+ mixtures using spectrophotometry is a problematic issue. A combined multivariate as partial least squares (PLS)–artificial neural network (ANN) was used to create and adjust a model and predict said cations in test and real sample sets. In this context, the calibration model is based on absorption spectra in the 400–900 nm range for 98 different mixtures of Fe3+ and Fe2+. Calibration matrices contained 1–12 and 1–10 μg ml−1 of Fe3+ and Fe2+, respectively. The detection limits for Fe3+ and Fe2+ were 0.53 and 0.14 μg ml−1, respectively. The root mean square error of prediction (RMSEP) for Fe3+ and Fe2+ with PLS‐ANN was 0.78, 1.65 and 1.062, 0.894 in Kalugan waterfall and Tehran tap water. This strategy can simultaneously determine Fe3+ and Fe2+ in real matrix samples, and the reliability of the determination is acceptable.

Metal organic framework encapsulated tamavidin-Gluc reporter: application in COVID-19 spike antigen bioluminescent immunoassay.

Enzyme linked immunosorbent assay (ELISA) is one of the most utilized serological methods to diagnose and identify etiologic agents of many infectious diseases and other physiologically important analytes. ELISA can be used either alone or adjunct to other diagnostic methods such as molecular arrays, and other serological techniques. Most ELISA assays utilize reagents that are proteinaceous in nature, which are not very stable and require cold-chain transport systems. Development of a desirable immunoassay requires stability of reagents used and its ability to be stored at room temperature without sacrificing the activity of the reagents or the protein of interest. Metal organic frameworks (MOFs) are a rapidly emerging and evolving class of porous polymeric materials used in a variety of biosensor applications. In this study, we introduce the use of MOFs to stabilize a universal reporter fusion protein, specifically, avidin-like protein (Tam-avidin2) and the small bioluminescent protein Gaussia luciferase (Gluc) forming the fusion reporter, tamavidin2-Gluc (TA2-Gluc). This fusion protein serves as a universal reporter for any assays that utilize biotin-avidin binding strategy. Using SARS-CoV2 S1 spike antigen as the model target antigen, we demonstrated that encapsulation of TA2-Gluc fusion protein using a nano-porous material, zeolitic imidazolate framework-8 (ZIF-8), allows us to store and preserve this reporter protein at room temperature for over 6 months and use it as a reporter for an ELISA assay. Our optimized assay was validated demonstrating a 0.26 μg mL-1 limit of detection, high reproducibility of assay over days, detection of spiked non-virulent SARS-COV2 pseudovirus in real sample matrix, and detection in real COVID-19 infected individuals. This result can lead to the utilization of our TA2-Gluc fusion protein reporter with other assays and potentially in diagnostic technologies in a point-of-care setting.

Synthesis of Zn metal–organic framework doped magnetic graphene oxide for preconcentration and extraction of cefixime followed by its measurement using HPLC

In this work, an attempt was made to develop a powerful method for the determination of cefixime, as a widely used cephalosporin antibiotic. The method was based on the facile extraction and preconcentration of cefixime using Zn metal–organic framework doped magnetic graphene oxide composite (ZnMOF@MGO), followed by its determination using high-performance liquid chromatography (HPLC). The high surface area, great stability, and distinct features of the new adsorbent made it ideal for very efficient interactions with analyte molecules. ZnMOF@MGO was able to effectively extract cefixime from the complex matrix of real samples. Furthermore, the application of the magnetic-solid phase extraction (MSPE) process provided a low-cost and simple extraction process with a reduced extraction time. The combination of a high-performance extraction with a potent HPLC system resulted in a highly sensitive and selective analytical detection method. The method was able to detect cefixime in a linear range of 0.5–130 ng mL−1, with a detection limit of 0.11 ng mL−1, no important interfering effect was caused by other examined drugs. It was examined for the analysis of cefixime content of pharmaceutical and biological samples and acceptable recovery values were obtained.

Ion-Selective Optodes Integrated Paper-Based Device for Simultaneous Colorimetric Quantification of Salivary Na&lt;sup&gt;+&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt; and Ca&lt;sup&gt;2+&lt;/sup&gt;

The quantification of electrolytes in biological fluids plays an important role for evaluating the human health condition. This work proposes a disposable and simple microfluidic paper-based analytical device (μPAD) for the quantitative colorimetric detection of salivary Na+, K+ and Ca2+, relying on ion-selective optodes (ISOs). Nanoscale ISOs composed of pluronic F-127 surfactant-based micelles were used as a colorimetric indicator system, reducing the assay time compared to the previously reported bulk membrane approach. Devices consist of three functionalized paper layers assembled by lamination, with the optical signal read out from the bottom layer. Saliva was chosen as the biological specimen because it is painlessly collected and easy-to-handle, which makes it suitable for POC assays. Simultaneous Na+, K+ and Ca2+ detection by a single μPAD was successfully confirmed by using aqueous metal ion samples with various concentrations of Na+, K+ and Ca2+ within the biologically relevant range. The simultaneous detection of the three cationic species enabled the correction of the three ion quantities by eliminating the interference from other ions using the calculated selectivity coefficients. For proof-of-concept, Na+ quantification in a human saliva sample was conducted by the developed μPADs. The calibration curve for this assay was prepared by applying artificial saliva to the μPADs. The concentrations of Na+ in spiked human saliva were also measured by the μPADs. The obtained recovery rates were 78-132 %, which indicates the quantification of the added Na+ in the real sample matrix. Finally, this μPAD was successfully integrated into a smartphone-based assay, which enables salivary electrolyte quantification in resource poor settings. The developed μPADs satisfy the criteria of low-cost (< $0.3/device), rapidity (< 5 min) and simple analytical procedure compared to the conventional ion-selective electrode (ISE) method.

Efficient use of Ferrate(VI) in the remediation of aqueous solutions contaminated with potential micropollutants: Simultaneous removal of triclosan and amoxicillin

Ferrate(VI) is a safer oxidant compared to the often used oxidant in various wastewater treatment plants since the ferrate(VI) is devoid with the generation of harmful by-products. Hence, the present study is aimed to obtain laboratory experimental data for the treatment of water adulterated with emerging micro-pollutant (triclosan and amoxicillin) using the ferrate(VI). The parametric studies enabled us to deduce the kinetics of ferrate(VI) removal. The molar stoichiometry of ferrate(VI) and micro-pollutant was obtained as 2:1. Further, the mineralization of triclosan and amoxicillin is obtained which further enhances the applicability of ferrate(VI) in the waste water treatment. The simultaneous removal of these two pollutants (triclosan and amoxicillin) are extensively studied using the ferrate(VI). Moreover, the pH dependent degradation using ferrate(VI) is enabled to deduce the mechanism of removal. Additionally, the real matrix samples using the natural spring water (Tuikhur water) spiked with these micro-pollutants showed that the ferrate(VI) efficiency is almost unaffected at least in the removal of these two micro-pollutants. This showed the selectivity of the ferrate(VI) in the treatment process.

Novel determination of Cd and Zn in soil extract by sequential application of bismuth and gallium thin films at a modified screen-printed carbon electrode

This study describes a novel electrochemical technique for the detection of bioavailable cadmium(II) (Cd) and zinc(II) (Zn), in real soil samples. This was made possible by the sequential deposition of bismuth and gallium thin films on modified screen-printed carbon electrodes (SPEs). A range of graphitic modifications were evaluated, and a reduced graphene oxide/graphitic carbon nitride (RGO/g-C3N4) modification proved most suitable. Electrochemical characterisation demonstrated superior stability, attributed to the functional groups of GO, and an increased electron transfer rate, attributed to the intercalated g-C3N4.For voltammetric analysis, cadmium was determined in acetate buffer (pH 4.6) using a bismuth thin film (BiTF). Zn was then determined in the same cell, after adjustment of the pH to 5.1, using a gallium thin film (GaTF). The rationale for two separate thin films is described. Optimisations, such as concentration of bismuth(III), gallium(III), potassium ferrocyanide, pH and deposition potentials, were conducted in the matrix of real samples. The LODs and LOQs were determined in the extracted soil matrix as 0.01 and 0.03 mg kg−1, respectively, for bioavailable Cd and 0.01 and 0.04 mg kg−1, respectively, for bioavailable Zn. Good agreement was observed for Cd and Zn levels in numerous soil samples when compared to the established technique of ICP-OES. This approach opens up the possibility for rapid on-site portable testing of Cd and Zn in real soil samples to determine the probability of Cd uptake by crops.

Simultaneous removal of crystal violet and methyl green in water samples by functionalised SBA-15

ABSTRACT In this paper, we have synthesised SBA-S4, as a mesoporous silica-based sorbent, via template method by functionalization of SBA-15 using the tetra-sulphide group. The prepared structure was applied to remove Crystal Violet (CV) and Methyl Green (MG) dyes with 100% efficiency. The obtained adsorbent, after and before the modification, was characterised by several techniques to explore textural properties, functional groups, and morphology. Design-Expert was applied to find the optimal values of adsorbent dosage, the solution pH, and the concentration of each dye as experimental variables. It was found that the isotherm model and kinetic rate order fitted Langmuir and pseudo-second-order, respectively. The maximum adsorption capacity of the studied sorbent was 67.6 and 39.4 mg g−1 for CV and MG, respectively. The results also showed that SBA-S4 had high efficiency for eliminating the studied analytes in tap water, well water, and river water as real matrix samples. Reusability and regeneration studies indicated that the studied sorbent can be applied more than 5 cycles with a negligible loss of efficiency.