Magnetic dispersive solid-phase extraction using a zeolite-based composite for direct electrochemical determination of lead(II) in urine using screen-printed electrodes

A chemiluminescence biosensor based on the peroxidase-like property of molybdenum disulfide/zirconium metal-organic framework nanocomposite for diazinon monitoring

BACKGROUND

Organophosphorus pesticides are widely used in agriculture owing to their high effectiveness as insecticides. Among these, diazinon is a common environmental contaminant that acts as an acetylcholinesterase (AChE) enzyme inhibitor. As the current methods are too expensive and time-consuming for routine analysis of diazinon, its trace monitoring by rapid and sensitive methods is critical to protect the environment and human health.

RESULTS

A biosensor was introduced for the indirect detection of diazinon using a molybdenum disulfide/zirconium metal-organic framework (MoS₂@MIP-202(Zr)) nanocomposite. The probe is based on the peroxidase mimic of the prepared nanocomposite on NaHCO₃-H₂O₂ chemiluminescence system as well as the inhibitory effect of diazinon on the enzymatic activity of AChE. The chemiluminescence signal is gradually decreased with an increase in diazinon concentration, and there is a linear relationship between the analytical signal and diazinon concentration. Under the optimum conditions, the calibration plot is linear in the concentration range of 0.5-300.0 nmol L^-1. The limit of detection and quantification limit of the method are 0.12 and 0.40 nmol L^-1, respectively. The inter-day and intra-day relative standard deviations (% RSD n = 5, diazinon concentration; 100 nmol L^-1) are 3.66 and 1.35%, respectively. The method was used for diazinon detection in real water samples, and the high relative recovery values for the spiked samples along with satisfactory results of a certified reference material analysis confirmed that the method is accurate and free from the matrix effect.

SIGNIFICANCE AND NOVELTY

A nano-probe based on the peroxidase-like property of MoS₂@MIP-202(Zr) nanocomposite was developed for the first time for indirect detection of residue levels of diazinon in water samples. The high stability of the nanocomposite makes it a good alternative for natural peroxidase enzymes such as horseradish peroxidase with low stability.

Accumulation of essential (copper, iron, zinc) and non-essential (lead, cadmium) heavy metals in Caulerpa racemosa, sea water, and marine sediments of Bintan Island, Indonesia

Background: Heavy metals are materials naturally occurring in nature and increase with a rise in human activity. Ex-mining areas and domestic waste from human settlements are sources of heavy metal contamination that enter and pollute water, which then accumulates in various organisms including the  Caulerpa racemosa community. The accumulation of heavy metals in  C. racemosa has a wide impact on the food chain in aquatic ecosystems and humans because this alga is a consumptive commodity.  

Methods: Sampling of  C. racemosa was carried out at seven sites on Bintan Island, Indonesia covering the eastern (Teluk Bakau, Beralas Pasir, Malang Rapat), northern (Berakit and Pengudang), western (Sakera), and southern parts (Tg. Siambang). Sampling was carried out during different monsoons, and heavy metals in water and sediment samples were measured to determine the heavy metal concentration. Heavy metals were analyzed by a spectrophotometric method using Atomic Absorption Spectrophotometry.  

Results: The results showed that heavy metal concentrations fluctuate according to changes in the wind season, which carry currents and spread pollutants into the water. The concentration of metal in the water is also from anthropogenic activities. The heavy metal content of cadmium (Cd), lead (Pb), copper (Cu), iron (Fe), and zinc (Zn) in  C. racemosa is high in locations close to settlements. Meanwhile, in seawater samples, Fe and Zn metals have the highest concentrations compared to others. 

Conclusions: Ex-bauxite mines are a source of Fe and Zn metal contamination in the environment, especially at Tg. Siambang. The levels of these heavy metals in the sediment are also high, as surface particle deposits accumulate at the bottom of the sediment. In general, the levels of heavy metals Cd, Pb, Cu, Fe, and Zn increase in the northern monsoon because the dynamics of the water transport greater heavy metal pollution.

Non-invasive electrochemistry-driven metals tracing in human biofluids

Wearable analytical devices represent the future for fast, de-centralized, and human-centered health monitoring. Electrochemistry-based platforms have been highlighted as the role model for future developments amid diverse strategies and transduction technologies. Among the various relevant analytes to be real-time and non-invasively monitored in bodily fluids, we review the latest wearable achievements towards determining essential and toxic metals. On-skin measurements represent an excellent possibility for humankind: real-time monitoring, digital/fast communication with specialists, quick interventions, removing barriers in developing countries. In this review, we discuss the achievements over the last 5 years in non-invasive electrochemical platforms, providing a comprehensive table for quick visualizing the diverse sensing/technological advances. In the final section, challenges and future perspectives about wearables are deeply discussed.

Electrochemical paper-based microfluidic device for on-line isolation of proteins and direct detection of lead in urine

In this work, we developed a microfluidic paper-based analytical device (μPAD) for the on-line isolation of proteins and the electrochemical detection of lead ions (Pb(II)) in urine samples. The patterned filter paper was prepared through the direct printing of microchannel patterns on filter paper using an office laser printer. The paper was modified with protein precipitant and was then coupled with a detachable three-electrode system. Experimental parameters, namely, modification reagents, microchannel length and width, deposition potential, and deposition time, were optimized. Then, the maximum protein concentration under which the device can function was obtained as 300 mg L^-1. The linear range was 10-500 μg L^-1 with a detection limit of 9 μg L^-1. The effectiveness of this device was demonstrated through the quantification of Pb(II) in urine samples and the results agreed with those of atomic absorption spectrometry (AAS).

Greenness of magnetic nanomaterials in miniaturized extraction techniques: A review

Green analytical chemistry principles should be followed, as much as possible, and particularly during the development of analytical sample preparation methods. In the past few years, outstanding materials such as ionic liquids, metal-organic frameworks, carbonaceous materials, molecularly imprinted materials, and many others, have been introduced in a wide variety of miniaturized techniques in order to reduce the amount of solvents and sorbents required during the analytical sample preparation step while pursuing more efficient extraction methods. Among them, magnetic nanomaterials (MNMs) have gained special attention due to their versatile properties. Mainly, their ability to be separated from the sample matrix using an external magnetic field (thus enormously simplifying the entire process) and their easy combination with other materials, which implies the inclusion of a countless number of different functionalities, highly specific in some cases. Therefore, MNMs can be used as sorbents or as magnetic support for other materials which do not have magnetic properties, the latter permiting their combination with novel materials. The greenness of these magnetic sorbents in miniaturized extractions techniques is generally demonstrated in terms of their ease of separation and amount of sorbent required, while the nature of the material itself is left unnoticed. However, the synthesis of MNMs is not always as green as their applications, and the resulting MNMs are not always as safe as desired. Is the analytical sample preparation field ready for using green magnetic nanomaterials? This review offers an overview, from a green analytical chemistry perspective, of the current state of the use of MNMs as sorbents in microextraction strategies, their preparation, and the analytical performance offered, together with a critical discussion on where efforts should go.

Application of magnetic nanomaterials in electroanalytical methods: A review

Magnetic nanomaterials (MNMs) have gained high attention in different fields of studies due to their ferromagnetic/superparamagnetic properties and their low toxicity and high biocompatibility. MNMs contain magnetic elements such as iron and nickel in metallic, bimetallic, metal oxide, and mixed metal oxide. In electroanalytical methods, MNMs have been applied as sorbents for sample preparation before the electrochemical detection (sorbent role), as the electrode modifier (catalytic role), and the integration of the above two roles (as both sorbent and catalytic agent). In this paper, the application of MNMs in electroanalytical methods have been classified based on the main role of the nanomaterial and discussed separately. Furthermore, catalytic activities of MNMs in electroanalytical methods such as redox electrocatalytic, nanozymes catalytic (peroxidase, catalase activity, oxidase activity, superoxide dismutase activity), catalyst gate, and nanocontainer have been discussed.

Magnetic dispersive solid-phase extraction using ZSM-5 zeolite/Fe2O3 composite coupled with screen-printed electrodes based electrochemical detector for determination of cadmium in urine samples

A novel, simple, fast, sensitive and environmentally friendly approach is presented to determine cadmium in urine samples, combining magnetic dispersive solid-phase extraction (MDSPE) for sample preparation and screen-printed carbon electrodes (SPCEs) for square-wave anodic stripping voltammetry. This association involves the miniaturization of sample preparation and measurement process. Firstly, cadmium was extracted directly from urine samples employing a ZSM-5/Fe₂O₃, then, the composite enriched with cadmium was deposited onto the SPCE and finally covered with a suitable electrolyte for electrochemical detection. Thereby, the elution and detection of cadmium were carried out in a single step. To optimize experimental parameters affecting MDSPE, a two-step multivariate strategy has been employed. The method has been evaluated under optimized extraction/elution conditions (i.e., type of sorbent, ZSM-5/Fe₂O_3; amount of sorbent, 10 mg; sample pH, 6.8; extraction time, 5.5 min; and HCl concentration, 0.5 M) using standard addition calibration. Standard addition calibration curves gave a good linearity in the range from 0 to 30 μg L^-1 with correlation coefficients ranging from 0.997 to 0.998 (N = 7). The limit of detection, evaluated empirically and statistically, ranged from 0.5 to 1.0 μg L^-1 and from 0.4 to 0.8 μg L^-1, respectively, which are lower than the threshold level established by the Ministry of Labour and Social Affairs (Spain) and World Health Organization for normal cadmium content in urine (i.e., 3.4 and 4.0 μg L^-1, respectively). The repeatability of the proposed method was evaluated at 5 and 20 μg L^-1 spiking levels obtaining coefficients of variation ranged between 12 and 15% (n = 6). A certified reference material (REC-8848/Level II) was analyzed to assess method accuracy finding 92% and 1.3 μg L^-1 as the recovery (trueness) and standard deviation values, respectively. Finally, the method was applied to spiked urine samples, obtaining good agreement between spiked and found concentrations (recovery ranged from 89 to 98% and CV values ranged from 7% to 14%). Therefore, this is a new and successful contribution to the portable total analytical systems.

Magnetic solid-phase extraction for speciation of mercury based on thiol and thioether-functionalized magnetic covalent organic frameworks nanocomposite synthesized at room temperature

A simple and practical magnetic solid-phase extraction high-performance liquid chromatography-inductively coupled plasma mass spectrometry (MSPE-HPLC-ICP-MS) method for extraction and determination of trace mercury species, including inorganic mercury (IHg), monomethylmercury (MeHg) and ethylmercury (EtHg), was developed. The MSPE adsorbent, urchin-like thiol and thioether-functionalized magnetic covalent organic frameworks (Fe₃O₄@COF-S-SH), was synthesized by coating covalent organic frameworks (COFs) on the surface of Fe₃O₄ nanoparticles at room temperature and then easily grafting 1,2-Ethanedithiol on the COFs. The as-prepared Fe₃O₄@COF-S-SH has strong adsorption capacity for IHg, MeHg and EtHg, with excellent static adsorption capacity: 571, 559 and 564 mg g^-1, respectively. The parameters influencing the extraction and enrichment had been optimized, including pH, adsorption and desorption time, composition and amount of the eluent, co-existing ions and dissolved organic materials etc. Under the optimized condition, the limit of detection (3δ) of the proposed method were 0.96, 0.17 and 0.47 ng L^-1 for IHg, MeHg and EtHg, and the developed method has high actual enrichment factors of 370, 395, 365-fold for IHg, MeHg and EtHg based on 200 mL samples, respectively. The high accuracy and reproducibility has been proved by the spiked recoveries (96.0‒108 %) in real water samples and determination of the certified reference material. Both the adsorption and desorption process can be completed within 5 min. The proposed method with simple operation, short pre-concentration time and high sensitivity has been successfully applied to mercury speciation at trace levels in the samples with complicated matrices, including underground water, surface water, sea water and fish samples.

Zeolitic imidazolate frameworks for use in electrochemical and optical chemical sensing and biosensing: a review

This review (with 145 refs.) summarizes the progress that has been made in the use of zeolitic imidazolate frameworks in chemical sensing and biosensing. Zeolitic imidazolate frameworks (ZIFs) are a type of porous material with zeolite topological structure that combine the advantages of zeolite and traditional metal-organic frameworks. Owing to the structural flexibility of ZIFs, their pore sizes and surface functionalization can be reasonably designed. Following an introduction into the field of metal-organic frameworks and the zeolitic imidazolate framework (ZIF) subclass, a first large section covers the various kinds and properties of ZIFs. The next large section covers electrochemical sensors and assays (with subsections on methods for gases, electrochemiluminescence, electrochemical biomolecules). This is followed by main sections on ZIF-based colorimetric and luminescent sensors, with subsections on sensors for metal ions and anions, for gases, and for organic biomolecules. The last section covers SERS-based assays. Several tables are presented that give an overview on the wealth of methods and materials. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Graphical abstract In recent years, ZIFs and their composites have been widely used as probes in chemical sensing, and these probes have shown great advantages over other materials. This review describes the current progress on ZIFs toward electrochemical, luminescence, colorimetric, and SERS-based sensing applications, highlighting the different strategies for designing ZIFs and their composites and potential challenges in this field.