Current Analytical Chemistry - Volume 17, Issue 7, 2021

Background: Studies have confirmed the ubiquitous presence of microplastics in every environmental compartment, and their number is rising year by year. Despite the fact that important efforts are being made in many countries to try to reduce microplastics contamination, it is very likely that their presence will continue to increase since plastic degradation is a long-term procedure. Current scientific data in this field is only the tip of a huge iceberg in which hand in hand research with scientists of different disciplines is absolutely necessary to draw a clear map of their origin, transport dynamics, distribution and effects. Methods: A brief overview (perspective article) of current research topics on microplastics, the problems that they must face as well as those gaps that should be solved in the future are reviewed. Results: Standardized and validated methodologies for microplastics quantification and identification are needed. The analysis of organic and inorganic contaminants retained onto microplastics is also a key issue. The study of the presence, behavior, and fate of microplastics in the environment (in all the environmental compartments), as well as the toxicity and dietary exposure studies, are also extremely necessary. Conclusion: A better understanding of the concentration, source, and hazards of microplastics in every environmental compartment is still needed, especially in the terrestrial environment and atmosphere. There is also the need of applying harmonized and validated analytical methodologies to provide feasible results and to allow a suitable comparison.

Background: The extensive industrialization and unrestricted development of dyeutilizing industries coupled with the shortage of proper effluent treatment methods have increased the water pollution. Disposal of dyes in a natural water system is a severe worldwide concern owing to the harmful effects on the ecosystem. Among the available wastewater treatment methods, adsorption is considered as a promising alternative in the elimination of dyes. Methods: There are a variety of ways for the modification of agro-waste, such as (i) acid modification (ii) alkali modification, (iii) surfactant modification, and (iv) preparation of activated carbon, etc. Moreover, numerous techniques have been used for the characterization of modified agro-waste, such as, SEM/EDAX, TEM, BET, TGA, and FTIR. Results: From the literature study, it was observed that the adsorption efficiency of various modified agro-waste is reliant on the nature of the adsorbent materials and different batch parameters, such as initial dye concentration, solution pH, adsorbent dose, and temperature of the system. In this way, these components must be thought about while evaluating the elimination of dye using various agrobased adsorbents. Conclusion: Modification of agricultural waste usually improved the adsorption capacity of adsorbents due to an escalation in the number of active adsorbing sites, enhancement in the porosity, increase in the surface area, and generation of new functional groups that favor the removal of dye from wastewater. Agro-waste materials being inexpensive, abundant, and renewable can be effectively exploited for the confiscation of dye from aqueous media.

Background: Plants are considered an important feedstock for cellulose, although algae can be used as a reservoir for the extraction of cellulose in its pure form. Cellulose nanofiber extracted from plant and algae gains more attention among researchers due to their size in the nano range, low cost for preparation, higher surface area available for tuning, outstanding mechanical properties and eco-friendly nature. However, the quality of nanofiber depends on the extraction procedure and feedstock used for their extraction. Furthermore, the extracted nanofiber from lignocellulosic biomass is not compatible with liquid and polymeric matrices due to less amount of functional groups present on their surface. Therefore, it is urged to comprehend the explicit protocol required for the extraction of highly resourceful nanofibers from specific lignocellulosic biomass and surface tuning strategy, which can augment their application in various fields. The present review targets to understand the various polysaccharides, lignin and production of cellulose nanofibers in an economical & efficient way with special attention on its implementation in environmental applications to mitigate the toxic pollutants from our surroundings. Methods: Research articles related to the cellulose types, feedstocks, physico-chemical features, various extraction and conversion techniques, functionalization methods, and applications on mitigating environmental pollution were collected and reviewed. This review article comprises sections which present various cellulose and nanocellulose types, feedstocks, followed by their extraction, characterization and applications in mitigation of environmental issues such as heavy metal contaminations. Results: Studies highlighted in the article detailed types of extraction protocols, so far developed and strategies applied to improve the salient properties of nanofibers for specific applications are enlightened. Conclusion: The functionalized or modified cellulose and nanocellulose have gained significant attention attributed to their unique characteristics, physico-chemical characteristics and efficiency in recovery of environmental pollutants. Thus, further exploitation of such natural resources in mitigation of various environmental issues and other related applications are to be maximized.

Background: There is an increasing demand for innovation in petroleum system replacements. Towards this aim, lignocellulosic biomass is suggested as a possible sustainable source for the manufacturing of fuels and chemical production. This paper aims to investigate different kinds of β-O-4 lignin model compounds for the production of value-added chemicals in the presence of ionic liquids. Especially, cheap β-O-4 lignin model guaiacol glycerol ether (GGE) (Guaifenesin) is introduced to produce valuable chemicals and novel products. Methods: The research related to chemical depolymerization of lignocellulosic biomass activity is reviewed and an account of different methods such as thermal and microwave for the last 10 years is presented. So, this work provides an excellent background for academic research and it gives an efficient strategy for the manufacturing of novel value-added chemicals at an industrial scale. Results: The review concludes that ionic liquid microwave-assisted synthesis is a power-saving, cost-efficient, fast reaction, and clean way with high selectively and purity for the production of high-value chemicals rather than conventional heating. Guaiacol and catechol are some of these valuable chemicals produced from β-O-4 lignin model compounds with high demands and large industrial scale prospects. Conclusion: The β-O-4 lignin model compounds such as guaiacol glycerol ether (GGE) (Guaifenesin) are a good platform for developing food materials, perfumery, biorefinery, and pharmaceutical industry by ionic liquids-assisted lignin depolymerization method.

Background: Dye contamination of natural water system is a severe problem due to the considerable enhancement in the industrial activities. As the dyes are highly visible, nonbiodegradable, and toxic in nature, they are considered as a severe source of water pollution. Therefore, it is imperative to develop an inexpensive, simple, effective, and easy technique for their elimination from wastewater. Methods: Luffa aegyptiaca peel (LuAP), kitchen waste was exploited as a low-priced biosorbent for the adsorptive elimination of cationic methylene blue (MB) dye. The influence of several batch parameters, i.e., adsorbent dose, pH of the solution, initial dye concentration, adsorbate/adsorbent contact time, and temperature were optimized for maximum adsorption of MB from aqueous media. Furthermore, thermodynamics, kinetics, and isotherm studies were also carried out in order to comprehend the dominant mechanism for the adsorptive elimination of MB. Results: The kinetic data for the adsorption of MB onto the LuAP followed closely by the pseudosecond- order (PSO) kinetics, and the adsorption equilibrium data were observed to be well demonstrated by Langmuir isotherm. The equilibrium was attained in 180 min with maximum sorption capacity of 52.63 mg/g at an adsorbent dose of 3 g/L, pH of 7, and temperature of 303 K. Thermodynamic study reveals that the removal of MB by LuAP is spontaneous and endothermic. Conclusion: It has been concluded that LuAP can be efficiently utilized for the confiscation of cationic MB dye from polluted water.

Background: Color effluents generated from the production industry of dyes and pigments and their use in different applications, such as textile, paper, leather tanning, and food industries, are high in color and contaminants that damage the aquatic life. It is estimated that about 10⁵ of various commercial dyes and pigments amounted to 7×10⁵ tons are produced annually worldwide. Ultimately, about 10-15% is wasted into the effluents of the textile industry. Chitin is abundant in nature, and it is a linear biopolymer containing acetamido and hydroxyl groups amenable to render it atmospheric by introducing amino and carboxyl groups, hence able to remove different classes of toxic organic dyes from colored effluents. Methods: Chitin was chemically modified to render it amphoteric via the introduction of carboxyl and amino groups. The amphoteric chitin has fully been characterized by FTIR, TGA-DTG, elemental analysis, SEM, and point of zero charges. Adsorption optimization for both anionic and cationic dyes was made by batch adsorption method, and the conditions obtained were used for studying the kinetics and thermodynamics of adsorption. Results: The results of dye removal proved that the adsorbent was proven effective in removing both anionic and cationic dyes (Acid Red 1 and methylene blue (MB)), at their respective optimum pHs (2 for acid and 8 for cationic dye). The equilibrium isotherm at room temperature fitted the Freundlich model for MB, and the maximum adsorption capacity was 98.2 mg/g using 50 mg/l of MB, whereas the equilibrium isotherm fitted the Freundlich and Langmuir model for AR1 and the maximum adsorption capacity was 128.2 mg/g. Kinetic results indicate that the adsorption is a two-step diffusion process for both dyes as indicated by the values of the initial adsorption factor (Ri) and follows the pseudo-second-order kinetics. Also, thermodynamic calculations suggest that the adsorption of AR1 on the amphoteric chitin is an endothermic process from 294 to 303 K. The result indicated that the mechanism of adsorption is chemisorption via an ion-exchange process. Also, recycling of the adsorbent was easy, and its reuse for dye removal was effective. Conclusion: New amphoteric chitin has successfully been synthesized and characterized. This resin material, which contains amino and carboxyl groups, is novel as such chemical modification of chitin hasn’t been reported. The amphoteric chitin has proven effective in decolorizing aqueous solution from anionic and cationic dyes. The adsorption behavior of amphoteric chitin is believed to follow chemical adsorption with an ion-exchange process. The recycling process for few cycles indicated that the loaded adsorbent could be regenerated by simple treatment and retested for removing anionic and cationic dyes without any loss in the adsorbability. Therefore, the study introduces a new and easy approach for the development of amphoteric adsorbent for application in the removal of different dyes from aqueous solutions.

Background: Application of nanotechnology in wastewater treatment is the solution to cope with the conflict between people’s increasing demand for water and the world-wide water shortage. The main goal of this study is to prepare modified carbon nanostructures (CNSs) from sugarcane bagasse waste (SCB) as effective adsorbents for removing toxic Cr(VI) ions from their aqueous solutions. Methods: The preparation of CNSs was performed via catalytic hydrothermal/carbonization of SCB. The resultant CNSs sample was oxidized by oxidation with HNO3/H2O2 (O-CNSs) and then followed by coating with diethylenetriamine (N-CNSs). Transmission electron microscope (TEM), scanning electron microscope attached to energy-dispersive X-ray (SEM/EDX), fourier transform infrared (FTIR) and nitrogen adsorption analyses were used to determine the morphology and surface properties of CNSs. Adsorption and desorption studies of Cr(VI) ions onto these modified CNSs were investigated. Effects of initial concentration of Cr(VI), pH of solution and temperature in the batch mode were estimated. Adsorption studies were analyzed by Langmuir, Freundlich and Dubinin- Radushkevich models. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were undertaken to follow the adsorption mechanism. Results: The prepared samples composed of carbon nanotubes and graphene sheets were evident by TEM and SEM. The adsorption of Cr(VI) is exothermic in nature, well-fitted with Langmuir, described by pseudo-second order kinetic model and then is uncontrolled by intraparticle diffusion step. It was found that the adsorption of Cr(VI) was higher uptake over O-CNSs (56 mg/g) than that by NCNSs (44 mg/g). This was ascribed to that the first sample is enriched with acidic O-functional groups and possessed higher specific surface area (188 m²/g). Desorption studies were achieved by HNO3 and NaOH reagents for recovering the Cr(VI) from O-CNSs. Results revealed that about 90% of Cr(VI) can be recovered by HNO3 more than that by NaOH till the third run. Conclusion: Two modified CNSs samples were successfully prepared from SCB. Adsorption of Cr(VI) is highly relied on initial concentration of Cr(VI), pH and temperature. The main factors controlling the adsorption behavior of Cr(VI) are the acidic functional groups and the accessible surface area on O-CNSs. Furthermore, the O-CNSs attained high stability in recycling tests for Cr(VI) removal.

Background: Sucralose is a high intensity artificial sweetener and chemically known as 1,6-dichloro-1,6-dideoxy-β-D-fructofuranosyl-4-chloro-4-deoxy-α-D-galactopyranoside. It is used as a sweetener and flavour enhancer in foods and beverages. Due to its high stability at wider temperatures and pH, it made its applicability in various food products throughout the world. As per Joint FAO/WHO Expert Group on Food Additives (JECFA) in 1990, the daily intake of sucralose is 0-15 mg/kg body weight. The literature reports suggest that sucralose has a possible health threat due to the presence of chlorine groups, thereby leading to several illnesses. The growing interest in the use of sucralose (SCL) in the foods makes it necessary in developing a fast, reliable, cost effective and reproducible analytical method to determine SCL in food samples. The detection of sucralose and other carbohydrates like fructose, glucose and sucrose is a challenging task owing to its: (i) unavailability of the charged functions and (ii) lack of absorption of strong chromophoric nature in the UV region. Therefore, separation of non-absorbing neutral molecules needs a careful procedure with suitable electrolyte systems. Methodology: An indirect UV detection capillary electrophoretic method is described for the separation of sucralose in different food samples. It was achieved by nucleophile substitution (SN2) in the presence of amine as background electrolytes. The morpholine buffer showed good buffering capacity in terms of migration time (< 8.0 min) and baseline stability when compared to other amine buffers (ethylamine, piperidine, triethylamine). The analytical applications of proposed method showed by recovery percentages of sucralose in real and spiked samples on intra and inter-day basis at optimum experimental conditions of 0.2 M buffer concentration and pH 12.0 at 230 nm UV detection. Results: The selection of BGE, UV detection wavelength, buffer concentration, buffer pH, cassette temperature and applied voltage was optimized to enhance the sensitivity and selectivity of the separation method. Recoveries obtained were ranging from 96.87 to 98.82% for real samples and 94.45 to 98.06% for spiked samples, respectively. Linearity was studied in the range of 2-10 mM, and showed a correlation coefficient of 0.9942. LOD and LOQ were found to be 0.3804 mg L^-1 and 1.5215 mg L^-1 with % RSD (n = 5) ± 1.27 and 1.19% with respect to migration time and peak area. Furthermore, to better understand the separation of sucralose with amine buffers, were investigated computationally using HOMO-LUMO calculations. The obtained results showed that the band gap decreases in the presence of amine moiety irrespective of its nature. Conclusion: In the study, a novel background electrolytic system was successfully applied to separate sucralose using indirect UV detector with capillary electrophoresis. The FTIR results confirmed that the interaction of sucralose with different amine buffers to better understand the separation chemistry behind sucralose and amine complexes. Moreover, computational results indicate that the direction of charge transfer from the amine functionality to the glucofuranosyl ring in each amine derivative of sucralose confirms the strong interaction between sucralose and amines, which led to the baseline separation of sucralose in different food samples.

Background: Because of their intrinsic ability to induce physiological effects in humans at low doses, pharmaceuticals and personal care products (PPCPs) are a unique group of emerging environmental pollutants. A number of studies have confirmed the occurrence of different PPCPs in the environment, which raises concerns about possible adverse effects on humans and wildlife. The removal of PPCPs from wastewaters has become a major activity to reduce pollution due to their adverse effects on humans and aquatic ecosystems. Methods: This study aimed to design a Quantitative Structure Activity Relationship (QSAR) model for the removal of 57 PPCPs from wastewater treatment plants (WWTPs) of historical data obtained from plants located in South Korea. The target compounds of PPCPs were optimised geometrically using a Forcite-Geometry code, assembled in Material Studio 2016. Results: The removal efficiency of PPCPs is dependent on several preliminary molecular descriptors including rotatable bonds (RBs), hydrogen bond donor (HBD), total molecular mass (TMM), binding energy (BE), atom count (AC), element count (EC), total energy (TE), total dipole (TD), highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). A Genetic Function Approximation (GFA) method was adopted to perform regression analysis and create correlation between experimental data (literature) and measured data (QSAR model). Conclusion: A QSAR model equation was established and used to predict removal efficiency of 57 PPCPs; the results obtained showed goodness of fit, R² greater than 0.90 indicating that the internal and external validations were also performed on the model.

Background: Due to an abrupt increase in the contamination of freshwater systems by dye-containing wastewater, there is an urgent need to find robust and greener adsorbents for the elimination of dyes from the contaminated water. As the dyes not only change the appearance of water but are also a cause of many serious problems, which can be some time mutagenic and carcinogenic. Methods: This research paper is based on the use of adsorbent made from the peel of jackfruit (POJ). The adsorbent derived from agriculture waste was at low cost and efficient for the elimination of methylene blue (MB) dye from aqueous media. Batch adsorption experiments were accompanied by varying the pH of the solution, contact time, POJ dosage, and initial MB concentration. Results: It was seen that adsorption of MB onto Jackfruit peel adsorbent follows pseudo-secondorder (PSO) kinetics and Langmuir isotherm with maximum biosorption capacity of 232.55 mg/g. The thermodynamic study revealed that the adsorption was spontaneous, endothermic, and associated with the rise in entropy. Conclusion: In view of the low-cost and promising adsorption efficiency, the present investigation submits that that POJ is novel and economically feasible adsorbent for the removal of MB from aqueous solutions.

Background: The approach for the determination of aminoimidazo-azaarenes (AIAs) is urgently required due to their mutagenic activity and potential carcinogenicity. For this purpose, a CdSe/ZnS quantum dots (CdSe/ZnS QDs)-embedded molecularly imprinted silica gel with high selectivity and sensitivity was successfully prepared and applied to analyze such target. Methods: Herein, CdSe/ZnS QDs acted as the fluorescent probe, and molecularly imprinted silica gel as a recognition probe was synthesized on the surface of QDs via sol-gel method. 2- Aminobenzimidazole, which has a similar structure with AIAs, as well as low cost and low toxicity, was selected as the dummy template. Results: The material has a high imprinting factor (IF=6.15); the linear range of CdSe/ZnS@MIP as a fluorescent sensing material for AIAs is 0.5-20.0 μg L^-1 with the limit of detection (LOD) of 0.25 μg L^-1 (3σ/s). Moreover, the fluorescent materials have been further applied to determine AIAs in beef floss and grilled fish fillet with satisfactory recoveries (82.8-110.8 %), and the relative standard deviation (RSD) is < 5.5%. Conclusion: The proposed CdSe/ZnS QDs-embedded molecularly imprinted silica gel can be used to easily and selectively detect AIAs.

Background: This work describes a fast, simple, sensitive, and low-cost method for the identification of resveratrol in different brands and varieties of red wines. Methods: It was developed based on a comparison of the UV-VIS spectra of the samples and samples enriched with different concentrations of the trans-resveratrol standard. The spectra were analyzed by chemometric principal component analysis (PCA) and multivariate calibration. Results: The PCA data indicated that only 4 main components made possible group samples based on the grape variety characteristics and/or production region. Conclusion: From the construction of partial least squares (PLS) and multiple linear regression (RLM) models, it was possible to predict the sample trans-resveratrol content with that sample showing similarities between the groups observed in the PCA and the samples used in the model constructions. The predicted trans-resveratrol present in these samples ranged from 0.29 to 23.3 mg L^-1. This multivariate method suggested a good predictive capacity of determination of resveratrol concentrations in commercial red wines.

Background: Bronze spears are weapons with unique regional characteristics of the Shu culture, Southwest China in the Bronze Age, which reflect the bronze manufacturing tradition and the utilization of mineral resources of ancestors. Previous studies mainly focused on the classification, the alloy composition, or the production of bronze spearheads of the Shu culture. The purpose of this paper was to make a comprehensive discussion on the Shu culture from the aspects of the relationship between typology and scientific characteristics, the differences in metal raw material selection with the Ba culture, and the contact with the culture in the Central Plains. Methods: In this study, typology, portable X-ray fluorescence spectrometry (pXRF) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) were used to analyze thirteen bronze spearheads unearthed from Shuangyuan site, an Eastern Zhou cemetery in Chengdu City, Sichuan Province, Southwest China. Results: The results show that the spearheads can be classified into three types in typology. All samples are tin-lead ternary bronzes, and the lead isotope data indicate the lead ore. Most spearheads show ordinary lead, and only one spearhead has highly radiogenic lead. Conclusion: The typical Shu-style bronze spearheads have distinct shapes but similar ore materials. Meanwhile, people of the Ba culture and the Shu culture used different metal sources to make bronze spearheads. In addition, a very special bronze spearhead suggests that ancestors of the Shu culture in the Eastern Zhou Dynasty imitated the late Shang culture in the Central Plains.

Background: Bisphenols A (BPA), bisphenol S (BPS), and bisphenol F (BPF) are manufactured chemicals found in food packaging, drink containers, lotions, toys, plastic PVC flooring, and water pipes. The aim of this work is to develop simple, rapid and reliable high-performance liquid chromatography with fluorescence detector (HPLC-FLD) method for simultaneous determination of bisphenols A (BPA), bisphenol F (BPF), and bisphenol S (BPS) in plastic packed dry fruits collected from Saudi Arabia markets. Methods: BPA, BPS and BPF in plastic packed dry fruits samples were extracted and clean up using packed Multi-Walled Carbon Nanotubes (MWCNTs) mini-column followed by analysis using HPLC-FLD. Results: The three BPs were separated within less than 12 min. The method was validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), precision (repeatability) and accuracy (recovery). Good linearity was obtained in the concentration range of 62.25-10000 μg/L for BPS and 6.25-1000 μg/L for BPA and BPF. The LODs and LOQs were found to be 1.07, 12.09, and 0.9939 μg/L and 3.56, 40.32 and 3.13 μg/L for bisphenols BPA, BPS, and BPF, respectively. Recoveries for analytes in the samples were all within the range of 87% to 104%. Conclusion: The method was successfully applied to real dry fruit samples (i.e, dry date (Ajwa), apricot, dry grapes and figs. The results obtained revealed that all of the tested BPs were present in the samples.