Analytical approach on surface active agents in the environment and challenges

Surface active agents (SAAs) are a class of compounds, which is used in variety of products such as detergents, fabric softeners, soaps, paints, adhesives, inks and anti-fogs. After the use of these products containing surfactants are disposed in water reservoirs. The separation and determination of surfactants from complex matrices become challenging for analytical chemists. The fundamentals on separation, preconcentration and analysis of surfactants employing different analytical instrumental techniques for qualitative and quantitative determination of surfactants in environmental samples are discussed. In addition, this compiled work enhanced our knowledge in learning about pathway mechanisms and the degree of their environmental loads. We also discussed the different aspects of method validation in the framework of quality control (QC) and quality assurance (QA). This review provides information on levels of SAAs in various environmental samples including soil, sediments, sewage wastewater, river wastewater and aerosols worldwide.     

Adsorption of a few heavy metals on natural and modified kaolinite and montmorillonite: a review

The feasibility of using two important and common clay minerals, kaolinite and montmorillonite, as adsorbents for removal of toxic heavy metals has been reviewed. A good number of works have been reported where the modifications of these natural clays were done to carry the adsorption of metals from aqueous solutions. The modification was predominantly done by pillaring with various polyoxy cations of Zr4+, Al3+, Si4+, Ti4+, Fe3+, Cr3+or Ga3+, etc. Preparation of pillared clays with quaternary ammonium cations, namely, tetramethylammonium-, tetramethylphosphonium- and trimethyl-phenylammonium-, N'-didodecyl-N, N'-tetramethylethanediammonium, etc, are also common. Moreover, the acid treatment of clays often boosted their adsorption capacities. The adsorption of toxic metals, viz., As, Cd, Cr, Co, Cu, Fe, Pb, Mn, Ni, Zn, etc., have been studied predominantly. Montmorillonite and its modified forms have much higher metal adsorption capacity compared to that of kaolinite as well as modified-kaolinite.     

Layer double hydroxides (LDHs)- based electrochemical and optical sensing assessments for quantification and identification of heavy metals in water and environment samples: A review of status and prospects

One of the most severe environmental problems is heavy metal contamination, putting the world's sustainability at risk. Much effort has been put into developing sensors that can be taken anywhere to detect the environmental effects of heavy metals. Sensitivity, selectivity, multiplexed detection ability, and mobility enhance significantly when nanoparticles and nanostructures are incorporated into sensors. LDHs (layered double hydroxides) have gotten much attention in analytical chemistry in recent years because of their benefits, including their large specific surface area, ease of synthesis, low cost, and high catalytic efficiency and biocompatibility. LDHs are often manufactured as nanomaterial composites or created with specialized three-dimensional structures depending on the application. However, in these settings, LDHs (as color indicators, extracting sorbents, and electrochemical sensing) are usually restricted. Upcoming signs of progress and development possibilities of LDHs in analytical chemistry are reviewed in this paper to assist overcome these problems. Furthermore, the approaches used in the design of LDHs, including structural aspects, are defined and assessed in preparation for future analytical applications. The latest advances in optical and electrochemical sensors to detect heavy metals are described in this review. The sorts and characteristics of LDHs will be explored first. We will then go into microelectrode (or nanoelectrode) arrays, nanoparticle-modified electrodes, and microfluidic optical and electrochemical sensing assays in detail. This paper also discusses design strategies for LDH-based nanostructured sensors and the advantages of using nanomaterials and nanostructures.     

燃烧过程中碱/碱土金属对重金属迁移转化影响的研究进展

碱/碱土金属广泛存在于各种固体燃料中，在燃烧过程中碱/碱土金属与燃料中重金属及其他矿物发生复杂的物理化学反应，从而影响重金属的迁移和转化。本研究主要介绍了碱/碱土金属对As、Se、Pb和Cr四种重金属迁移转化的影响规律，包括碱金属和碱土金属对重金属迁移转化的影响，颗粒物团聚与黏结对重金属排放的影响三个方面。碱/碱土金属能够抑制重金属的挥发：碱金属与Cl元素的结合，降低了PbCl₂的生成；碱金属的存在有利于提升高岭土对Pb的吸附效率；碱/碱土金属可以与As和Se形成稳定的化合物。但同时需要注意碱/碱土金属与Cr的部分结合产物中，Cr以六价态存在，具有较高的毒性。碱/碱土金属对于团聚现象发生，分别起到了促进和抑制作用，适当含量的碱金属有利于减少重金属的释放。通过总结碱/碱土金属对重金属迁移转化的影响规律，以期为降低重金属的危害提供思路。     

微塑料介导重金属在陆生植物中迁移及生物效应的影响

随着地膜在现代化农业中的广泛应用,微塑料在土壤中的残留问题日益严重。环境中释放的微塑料可能会与先前存在的重金属相互作用,导致生物效应(生物积累/毒性),并对人类健康和农产品安全构成威胁。目前,大多数研究集中于单一影响因素在土壤系统中的暴露和转化分析,有关微塑料和共存金属对环境联合影响的相当有限。本文综述了微塑料与重金属来源、相互作用机理与影响因素的研究现状,阐述了陆生植物对二者联合污染的生理响应。此外,未来的研究还应重点探讨微塑料与重金属共同在植物上暴露的具体分子机制、通过食物链对人类健康的影响、与其他混合污染物联合作用及微塑料老化过程对重金属迁移动态变化过程的影响。     

Analytical methods for the assessment of endocrine disrupting chemical exposure during human fetal and lactation stages: A review

In the present work, a review of the analytical methods developed in the last 15 years for the determination of endocrine disrupting chemicals (EDCs) in human samples related with children, including placenta, cord blood, amniotic fluid, maternal blood, maternal urine and breast milk, is proposed. Children are highly vulnerable to toxic chemicals in the environment. Among these environmental contaminants to which children are at risk of exposure are EDCs —substances able to alter the normal hormone function of wildlife and humans—. The work focuses mainly on sample preparation and instrumental techniques used for the detection and quantification of the analytes. The sample preparation techniques include, not only liquid–liquid extraction (LLE) and solid-phase extraction (SPE), but also modern microextraction techniques such as extraction with molecular imprinted polymers (MIPs), stir-bar sorptive extraction (SBSE), hollow-fiber liquid-phase microextraction (HF-LPME), dispersive liquid–liquid microextraction (DLLME), matrix solid phase dispersion (MSPD) or ultrasound-assisted extraction (UAE), which are becoming alternatives in the analysis of human samples. Most studies focus on minimizing the number of steps and using the lowest solvent amounts in the sample treatment. The usual instrumental techniques employed include liquid chromatography (LC), gas chromatography (GC) mainly coupled to tandem mass spectrometry. Multiresidue methods are being developed for the determination of several families of EDCs with one extraction step and limited sample preparation.     

Pharmaceuticals and their metabolites in the marine environment: Sources,analytical methods and occurrence

The occurrence of pharmaceuticals in the environmental waters is a global concern. There is little research conducted on the monitoring of pharmaceuticals in the marine environment. In this article, the occurrence of pharmaceuticals and their metabolites in the coastal waters as well as associated risks related to their uptake by marine organisms are critically reviewed. The literature showed antibiotics as the most plentiful pharmaceuticals in the marine environment. Other therapeutic classes of pharmaceuticals appeared prominently in the marine environment are non-steroidal anti-inflammatory drugs and β-blockers, while gemfibrozil and carbamazepine were singled-out as the most studied lipid regulator and antiepileptic, respectively. Some pharmaceuticals have been found present in the marine organisms that are regarded as important food sources for humans. We reviewed the negative effects associated with the presence of pharmaceuticals in the marine environment. This article is concluded by deliberating on the possible future studies in this research niche area.     

Microbiological analysis of seawater and sediments in urban shorelines: Occurrence of heavy metals resistance bacteria on Chennai beaches, Bay of Bengal

The present study aims to evaluate the microbial diversity of bacteria, fungi and other pathogenic microorganisms present in seawater and sediments from Chennai shoreline (southeast coast of India).Chennai beaches are heavily polluted with untreated sewage effluents; municipal sewage disposal and recreational activities. Seawater was heavily contaminated with coliforms, Vibrio and Pseudomonas compare to sediment microbial contamination. Isolated bacteria are mostly pathogenic microorganisms including Vibrio, Pseudomonas, Coliforms, Salmonella and Shigella. Another potential environmental threat noticed was heavy metal resistance of these pathogenic strains against 50 mM of Ni, Cr, Cu, Co, Pb and Hg. Statistical analyses revealed that the Chennai coast may cause health risk to the recreational users and fisher folk, ultimately warrants environmental quality management to control microbial contamination     

In-situ electrochemical and piezogravimetric studies on the application of macrocyclic resorcinarene tetramer in the development of chemically-modified heavy metals ions detection platform in aqueous media

The new application of C-dec-9-enylcalix[4]resorcinarene (R₁), as an ionophore to detect heavy metals (HMs) cations (Cd²⁺, Hg²⁺, Cu²⁺, and Pb²⁺) in the aqueous media has been investigated through the preparation of an effective mass-sensitive sensor via the exploitation of a flow-type QCM-I technique. By adjusting the ions’ amounts in model solutions over a wide range of concentrations, acquired changes in the oscillating frequency related to the loading of metal ions on the sensor’s surface were gained, and thus favorable metrological parameters displaying the lowest detection limit (LOD) associated with copper ions (10 ppb). Simultaneously, a novel voltammetric sensor was prepared by modifying gold screen-printed electrodes (SPEs) with R₁. Electrochemical characterization employing CV, SWV, and EIS was carried out, showing the success of the electrode modification. Then, the experimental conditions of supporting electrolyte, pH, accumulation time, and accumulation potential were optimized to achieve an enhanced detection. The R₁@SPE sensor simultaneously detected the HMs (Cd²⁺, Hg²⁺, Cu²⁺, Pb²⁺), and the lowest LOD was associated with Pb²⁺ (0.19 ppb). The selectivity evaluation of the electrochemical sensor was performed by studying the effect of interferences majorly present in water sources (Mg²⁺, Ni²⁺, Zn²⁺, Al³⁺, and K⁺) on the SWV detection signals, and it was revealed that the interfering ions did not affect the simultaneous detection of the studied HMs (RSD less than 5%), the voltammetric sensors also presented excellent repeatability and reproducibility (RSD less than 5%).     

Analytical methods for the determination of mixtures of bisphenols and derivatives in human and environmental exposure sources and biological fluids. A review

Bisphenol A (BPA) is ubiquitous in humans and the environment. Its potential adverse effects through genomic and non-genomic pathways have fostered BPA replacement by bisphenol analogs that, unfortunately, exert similar adverse effects. Many of these analogs, as well as their derivatives, have already found in humans and the environment and major concerns have arisen over their low dose- and mixture-related effects. This review aims to discuss the characteristics of the main analytical methods reported so far for the determination of mixtures of bisphenol analogs and/or derivatives in human and environmental exposure sources and biological fluids. Approaches followed for removal of background contamination, sample preparation and separation and detection of mixtures of bisphenols and derivatives are critically discussed. Sample treatment is matrix-dependent and common steps include analyte isolation, removal of interferences, evaporation of the extracts and solvent reconstitution. Separation and quantification has been almost exclusively carried out by liquid chromatography tandem mass spectrometry (LC-MS/MS) or gas chromatography mass spectrometry (GC–MS), in the last case prior derivatization, but LC-fluorescence detection has also found some applications. Main characteristics, advantages and drawbacks of these methods will be comparatively discussed. Although at an early stage, some approaches for the assessment of the risk to mixtures of bisphenols, mainly based on the combination of chemical target analysis and toxicity evaluation, have been already applied and they will be here presented. Current knowledge gaps hindering a reliable assessment of human and environmental risk to mixtures of bisphenols and derivatives will be outlined.     

Advances in the scaffolds fabrication techniques using biocompatible polymers and their biomedical application: A technical and statistical review

With the advancement in tissue engineering, researchers are working hard on new techniques to fabricate more advanced scaffolds from biocompatible polymers with enhanced porosity, appropriate mechanical strength, diverse shapes and sizes for potential applications in biomedical field in general and tissue engineering in particular. These techniques include electrospinning, solution blow spinning, centrifugal spinning, particulate leaching (salt leaching), freeze-drying, lithography, self-assembly, phase separation, gas foaming, melt molding, 3-D printing, fiber mesh and solvent casting. In this article we have summarized the scaffold’s fabrication techniques from biocompatible polymers that are reported so far, the recent advances in these techniques, characterization of the physicochemical properties of scaffolds and their potential applications in the biomedical field and tissue engineering. The article will help both newcomers and experts working in the biomedical implant fabrication to not only find their desired information in one document but also understand the fabrication techniques and the parameters that control the success of biocompatible polymeric scaffolds. Furthermore, a static analysis of the work published in all forms on the most innovative techniques is also presented. The data is taken from Scopus, restricting the search to biomedical fields and tissue engineering.     

Excited-state nonadiabatic dynamics simulations on the heptazine and adenine in a water environment: A mini review

Studying the excited-state decay process is crucial for materials research because what happens to the excited states determines how effective the materials are for many applications, such as photoluminescence and photocatalysis. The high computational cost, however, limits the use of high-accuracy theoretical approaches for analyzing research systems containing a significant number of atoms. Time-dependent density functional theory is a practical approach to investigate the photorelaxation processes in these systems, as demonstrated in the studies of the excited-state decays of heptazine-water clusters and adenine in water described in this review. Here, we highlight the importance of conical intersections in the excited-state decay processes of these systems using the aforementioned examples. In the heptazine-water and adenine-water systems, these intersections are associated with the photocatalytic water splitting reaction, caused by a barrierless reaction called water to adenine electron-driven proton transfer. We expect the result would be helpful for researching the excited-state decays of graphitic carbon nitride materials and DNA nucleotides.     

A comparative study on the single-scan and multiple-scan techniques in differential scanning calorimetry: Application to the crystallization of the semiconducting Ge0.13Sb0.23Se0.64 alloy

A method has been developed for analysing the evolution with time of the volume fraction transformed and for calculating the kinetic parameters at non-isothermal reactions in materials involving formation and growth of nuclei. By considering the assumptions of extended volume and random nucleation, a general expression of the fraction transformed as a function of time has been obtained in isothermal crystallization processes. Considering the mutual interference of regions growing from separate nuclei the Johnson–Mehl–Avrami equation has been deduced as a particular case. The application of the transformation rate equation to the non-isothermal processes has been carried out under the restriction of a nucleation which takes place early in the transformation and the nucleation frequency is zero thereafter. Under these conditions, the kinetic parameters have been deduced by using the techniques of data analysis of single-scan and multiple-scan. The theoretical method developed has been applied to the glass-crystal transformation kinetics of the semiconducting Ge_0.13Sb_0.23Se_0.64 alloy. The kinetic parameters obtained according to both techniques differ by only about 2.5%, which confirms the reliability and accuracy of the single-scan technique when calculating the above-mentioned parameters in non-isothermal transformation processes. The phases at which the above-mentioned semiconducting glass crystallizes after the thermal process have been identified by X-ray diffraction. The diffractogram of the transformed material shows that microcrystallites of Sb₂Se₃ and GeSe are associated with the crystallization process, remaining a residual amorphous matrix.