Latest approaches on green chemistry preconcentration methods for trace metal determination in seawater--a review

A new approach for the determination of As, Cu, and Pb in seawater samples using manganese oxide octahedral molecular sieve as a sorbent for dispersive solid-phase microextraction

This study introduces a novel method for preconcentrating As, Cu, and Pb from seawater samples using manganese oxide octahedral molecular sieve (OMS-2), as a sorbent, and the analysis by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The OMS-2 nanomaterial was synthesized and characterized using X-ray diffraction and scanning electron microscopy, revealing a crystallite size of 20.9 nm and a typical needle-like morphology of cryptomelane structure. To optimize the ICP-OES operating conditions and the preconcentration process, a central composite design was used. The optimal conditions for ICP-OES analyses were 1200 W and 0.7 L min-1 for the levels of the radio frequency potential (RF) and nebulization gas flow rate, respectively. The optimal conditions for the adsorption process were achieved at a pH of 6.5, 30 mg of OMS-2, and 35 min of stirring time, in the presence of the sample matrix. The enrichment factors obtained were 66, 45, and 21, and a limit of detection of 0.3, 0.1, and 2.1 μg L-1 for As, Cu, and Pb, respectively. The recovery tests ranged from 80 % to 120 %. The method was successfully applied to determine As, Cu, and Pb in seawater samples.

What dead seaweeds can tell us about metal uptake and their application to control marine pollution

The mechanisms of trace element uptake by seaweeds are still unknown, despite being key to understand the impact of pollution in coastal environments. This knowledge gap, in addition to the lack of standardization, have also hindered the use of seaweeds to monitor seawater pollution. To address these shortcomings, we tested the use of devitalization as a pre-exposure treatment for brown seaweed transplants, and we compared devitalized and fresh transplants to gain some insights into the mechanisms of element uptake. We exposed four types of Fucus vesiculosus transplants in 6 sites for 4, 8 and 20 days: fresh and devitalized (dried or boiled) algal segments held in mesh bags, and whole algal thalli imitating natural conditions. We then determined he concentrations of 11 trace elements in the algal tissues. The element concentrations were highest in the devitalized transplants, but the material lost consistency and weight throughout the exposure period, limiting their use to short periods. We proposed several factors that may contribute to the different accumulation patterns between treatments, and examined the implications for the uptake mechanisms, revealing that two of the most important are surface adsorption of sediment particles and chemical bounds to extracellular components.

A Chelating Resin of EDTA-Type Modified Cross-Linking Polystyrene to Preconcentrate Trace Metals for Seawater Detection

The determination of trace metals in seawater is an important project of marine environmental monitoring. However, the presence of many alkali metal ions with high concentration, such as sodium ion, seriously interferes with the detection limit and accuracy of atomic absorption spectrometry (AAS, flame/graphite furnace integrated). The conventional chemical methods for the enrichment of trace metals are complex, and low boiling point organic solvents are used. In this paper, a kind of commercial cross-linked polystyrene resin microspheres was chloromethylated and aminated to introduce EDTA-type amino polycarboxylic groups and then loaded in a column as the absorption filler. A set of seawater pretreatment and enrichment devices was designed and assembled. The enriching process and conditions of trace Cu, Zn, Pb, and Cd in standard seawater were studied. 10 g of the modified resin could enrich the equivalent seawater and remove successfully the light metal ions. pH = 5∼9 and 0.2 mL/min of the flow rate were the suitable conditions for preconcentration. The enriched metal ions in the eluent were analyzed on the AAS. Compared with the conventional solvent method, the novel material and enrichment device have high preconcentration efficiency, strong anti-interference ability, and low cost and could be directly applied for routine seawater detection.

Capillary-Assisted Molecular Pendulum Bioanalysis

The development of robust biosensing strategies that can be easily implemented in everyday life remains a challenge for the future of modern biosensor research. While several reagentless approaches have attempted to address this challenge, they often achieve user-friendliness through sacrificing sensitivity or universality. While acceptable for certain applications, these trade-offs hinder the widespread adoption of reagentless biosensing technologies. Here, we report a novel approach to reagentless biosensing that achieves high sensitivity, rapid detection, and universality using the SARS-CoV-2 virus as a model target. Universality is achieved by using nanoscale molecular pendulums, which enables reagentless electrochemical biosensing through a variable antibody recognition element. Enhanced sensitivity and rapid detection are accomplished by incorporating the coffee-ring phenomenon into the sensing scheme, allowing for target preconcentration on a ring-shaped electrode. Using this approach, we obtained limits of detection of 1 fg/mL and 20 copies/mL for the SARS-CoV-2 nucleoproteins and viral particles, respectively. In addition, clinical sample analysis showed excellent agreement with Ct values from PCR-positive SARS-CoV-2 patients.

Rapid and green detection of manganese in electrolytes by ultraviolet-visible spectrometry to control pollutant discharge

Controlling the manganese (Mn²⁺) concentration is important to product quality in the electrolytic manganese industry. Conventional methods for detecting Mn²⁺ are complex and reagent-consuming, which makes them slow and polluting. It is of great significance to develop a new fast and environmentally friendly method to quantify Mn²⁺ in electrolyte. The characteristic ultraviolet-visible (UV-vis) absorbance at 401 nm of Mn²⁺ will vary linearly with the Mn²⁺ concentration after data correction. Adjusting the pH, calibrating the spectral bandwidth (SBW) and optical path length (OPL), and subtracting the interference from coexisting substances by linear interpolation improve the measuring accuracy. Mn²⁺ concentration can be determined by direct fast UV-vis absorbance measurement at characteristic peaks without using harmful reagents which facilitates such measurement to be applicated as on-line detection method for electrolytic manganese industry. The method developed in this study will help achieve the goal of improving the detection speed while cutting back on pollutant discharge from concentration analysis process in electrolytic manganese industry.

Source apportionment and deposition of dustfall-bound trace elements around Tabriz, Iran

The monthly and spatial variations of atmospheric dustfall (DF) and their elemental components were determined. The DF sampling was performed using the ASTM method D-1739 from April 2017 to March 2018 in four urban and suburb sampling sites around Tabriz, Iran. The ICP-OES was utilized for the determination of the elemental components of DF.The results showed that the level of DF varied from 1.3 to 27.6 (8.0 ± 3.4) g/m2.month during the sampling period, and the level of DF was higher in warm seasons than cold seasons. Also, it was revealed that the mean DF has a direct and significant relationship with temperature, wind speed, and relative humidity.The elements of Fe (11,997-17,093 mg/Kg and 71-81%) and Al (2903-6852 mg/Kg and 14-25%), which are the main elements of the Earth crust, were the dominant metals of DF among the analyzed elements. The lowest average value of the enrichment factor (EF) was for Al and was < 1, while the highest EF belonged to Hg, Pb, Cu, Sr, Mn, Co, Ni, and Cr, which were > 10 in all the sites, indicating that anthropogenic emission sources spread a considerable amount of trace elements in DF compared to the Lake Urmia bed or soil. The EF values for various elements (except than Cu and Hg) in cold seasons considerably increased compared to warm seasons.In all the study sites, Fe (540-1307 mg/m2.yr) had the highest deposition rates among the metals. This study revealed that the Earth crust is the main source of DF in the region.

Temporal and spatial variations of deposition and elemental composition of dust fall and its source identification around Tabriz, Iran

Coarse particles are primarily deposited via sedimentation, commonly referred as dust fall (DF). This study presented the monthly and spatial variations of atmospheric DF and their elemental components (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, Sr, Ti, V, Si, and Hg). Dust samples were collected from four urban and suburban sampling sites around Tabriz, Iran, by using the ASTM method D-1739 during April to September 2017. Moreover, the ICP-OES was used to determine metal components of the DF. The obtained results showed that the DF amount ranged between 1.8-27.6 (7.4 ± 5.6) g/m2.month. The elements of Fe (11863-13,906 mg/Kg and 85%-89%), Al (858-1205 mg/Kg and 4%-8%), and Si (274-386 mg/Kg) were the dominant elemental concentrations of the DF. The average value of enrichment factor (EF) for Hg, Pb, Cu, Sr, Co, Ni, Mn, and V was greater than 10 in all the samples, showing that anthropogenic sources emit a considerable amount of elements in DF rather than the soil or Urmia lake bed. The result of correlations between the concentration of dust fall with humidity, temperature, wind speed, and precipitation showed that there was a direct relationship between the amount of dust fall and wind speed while humidity, precipitation, and temperature were inversely proportional to the amount of dust fall. This study revealed that earth crust and anthropogenic activities such as vehicle traffic, combustion of fossil fuel, and different industrial activities were the main sources of the DF in the studied areas.

Development of magnetic porous coordination polymer adsorbent for the removal and preconcentration of Pb(II) from environmental water samples

A novel porous coordination polymer adsorbent (BTCA-P-Cu-CP) based on a piperazine(P) as a ligand and 1,2,4,5-benzenetetracarboxylic acid (BTCA) as a linker was synthesized and magnetized to form magnetic porous coordination polymer (BTCA-P-Cu-MCP). Fourier transform infrared (FTIR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscope(FESEM), energy-dispersive X-ray spectroscopy(EDS), CHN, and Brunauer-Emmett-Teller(BET) analysis were used to characterize the synthesized adsorbent. BTCA-P-Cu-MCP was used for removal and preconcentration of Pb(II) ions from environmental water samples prior to flame atomic absorption spectrometry(FAAS) analysis. The maximum adsorption capacity of BTCA-P-Cu-MCP was 582 mg g^-1. Adsorption isotherm, kinetic, and thermodynamic parameters were investigated for Pb(II) ions adsorption. Magnetic solid phase extraction (MSPE) method was used for preconcentration of Pb(II) ions and the parameters influencing the preconcentration process have been examined. The linearity range of proposed method was 0.1-100 μg L^-1 with a preconcentration factor of 100. The limits of detection and limits of quantification for lead were 0.03 μg L^-1 and 0.11 μg L^-1, respectively. The intra-day (n = 7) and inter-day (n = 3) relative standard deviations (RSDs) were 1.54 and 3.43% respectively. The recoveries from 94.75 ± 4 to 100.93 ± 1.9% were obtained for rapid extraction of trace levels of Pb(II) ions in different water samples. The results showed that the BTCA-P-Cu-MCP was steady and effective adsorbent for the decontamination and preconcentration of lead ions from the aqueous environment.

Novel chiral ionic liquids stationary phases for the enantiomer separation of chiral acid by high-performance liquid chromatography

Novel chiral ionic liquid stationary phases based on chiral imidazolium were prepared. The ionic liquid chiral selector was synthesized by ring opening of cyclohexene oxide with imidazole or 5,6-dimethylbenzimidazole, and then chemically modified by different substitute groups. Chiral stationary phases were prepared by bonding to the surface of silica sphere through thioene "click" reaction. Their enantioselective separations of chiral acids were evaluated by high-performance liquid chromatography. The retention of acid sample was related to the counterion concentration and showed a typical ion exchange process. The chiral separation abilities of chiral stationary phases were greatly influenced by the substituent group on the chiral selector as well as the mobile phase, which indicated that, besides ion exchange, other interactions such as steric hindrance, π-π interaction, and hydrogen bonding are important for the enantioselectivity. In this report, the influence of bulk solvent components, the effects of varying concentration, and the type of the counterion as well as the proportion of acid and basic additives were investigated in detail.

Green approach for ultratrace determination of divalent metal ions and arsenic species using total-reflection X-ray fluorescence spectrometry and mercapto-modified graphene oxide nanosheets as a novel adsorbent

A new method based on dispersive microsolid phase extraction (DMSPE) and total-reflection X-ray fluorescence spectrometry (TXRF) is proposed for multielemental ultratrace determination of heavy metal ions and arsenic species. In the developed methodology, the crucial issue is a novel adsorbent synthesized by grafting 3-mercaptopropyl trimethoxysilane on a graphene oxide (GO) surface. Mercapto-modified graphene oxide (GO-SH) can be applied in quantitative adsorption of cobalt, nickel, copper, cadmium, and lead ions. Moreover, GO-SH demonstrates selectivity toward arsenite in the presence of arsenate. Due to such features of GO-SH nanosheets as wrinkled structure and excellent dispersibility in water, GO-SH seems to be ideal for fast and simple preconcentration and determination of heavy metal ions using methodology based on DMSPE and TXRF measurement. The suspension of GO-SH was injected into an analyzed water sample; after filtration, the GO-SH nanosheets with adsorbed metal ions were redispersed in a small volume of internal standard solution and deposited onto a quartz reflector. The high enrichment factor of 150 allows obtaining detection limits of 0.11, 0.078, 0.079, 0.064, 0.054, and 0.083 ng mL(-1) for Co(II), Ni(II), Cu(II), As(III), Cd(II), and Pb(II), respectively. Such low detection limits can be obtained using a benchtop TXRF system without cooling media and gas consumption. The method is suitable for the analysis of water, including high salinity samples difficult to analyze using other spectroscopy techniques. Moreover, GO-SH can be applied to the arsenic speciation due to its selectivity toward arsenite.

Sensitive detection of atrazine in tap water using TELISA

Sensitive detection of atrazine in tap water using a universal platform: novel TELISA.