Rapid Magnetic Dispersive solid phase extraction to preconcentration/determination of Cd and Pb in aqueous samples

A new magnetic dispersive solid phase extraction (MDSPE) method and graphite furnace atomic absorption spectrometry (GFAAS) have been combined for the analysis of Cd and Pb in environmental samples. For the preconcentration, a shell structured Fe3O4@graphene oxide nanospheres was synthetized and characterized. The material was suspended in the ionic liquid 1-n-butyl-3-metilimidazolium tetrafluoroborate [BMIM][BF4], the obtained stable colloidal suspension is named ferrofluid. GO presents excellent adsorbent properties for organic species due to the presence of the electronic π system. For this reason, the organic ligand [1,5-bis-(2-dipyridyl) methylene] thiocarbonohydrazide (DPTH) was used in order to form organic complexes of Cd and Pb. Once the DPTH ligand has been added to sample, the ferrofluid was injected and finely dispersed in the sample solution in order to extract the formed chelates. The complete adsorption of the chelates took place within few seconds then, the solid was separated from the solution with the aid of a strong magnet. Cd and Pb ions were desorbed from the material with 1 mL of acid nitric 5% solution and quantified by GFAAS. All experimental and instrumental variables were optimized. The analytical performances of the optimized method were: EF (Enrichment factor): 200 with LODs (detection limit): 0.005 and 0.004 µg L-1 and LOQs (determination limit): 0.017 and 0.013 µg L-1, for Cd and Pb, respectively. The reliability of the developed procedure was tested by relative standard deviation (% RSD), which was found to be < 5%. The accuracy of the proposed method was verified using certified reference materials (SLRS-5, SPS-SW2, and BCR-723) and by determining the analyte content in spiked aqueous samples. Sea waters and tap water samples collected from Málaga (Spain) were also analysed. The determined values were in good agreement with the certified values and the recoveries for the spiked samples were around 100% in all cases.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Magnetic graphene molecularly imprinted polypyrrole polymer (MGO@MIPy) for electrochemical sensing of malondialdehyde in serum samples

A modified screen-printed carbon electrode (SPCE) has been designed and fabricated for the determination of malondialdehyde (MDA), an important biomarker of oxidative stress. Magnetic graphene oxide (MGO) was synthesized and coated by a molecularly imprinted polypyrrole (MIPy) for the preparation of a novel hybrid nanomaterial (MGO@MIPy). The nanocomposite has been characterized using different spectroscopic and imaging techniques. The coupling of MIPy with MGO allows the exploitation of the magnetic properties of the material for separation, preconcentration and manipulation of analyte which is selectively captured onto the MIPy surface of the nanocomposite. Besides, the derivatization of MDA with diaminonaphtalene (DAN) was carried out, resulting in a more electroactive molecule (MDA-DAN). MDA-DAN was used as template in the synthesis of MIPy. SPCEs were employed to monitor the differential pulse voltammetry (DVP) levels of the material, which is related to the amount of the captured analyte. Under optimum conditions, the nanocomposite-based sensing system has proved to be suitable for the monitoring of MDA, presenting a wide linear range (0.01–100 µM), high sensitivity (experimental LOQ = 0.01 µM) and precision (RSD = 4%). For validation purposes, three chicken serum samples were analysed by external calibration, obtaining recoveries values close to 100% for all the spiked tests. Finally, the developed electrochemical sensor demonstrated to be adequate for bioanalytical application, presenting an excellent analytical performance for the routine monitoring of MDA in serum samples.The Spanish Ministry of Science and Innovation, JJCC Castilla-La Mancha and Junta de Andalucía are gratefully acknowledged for funding this work with Fellowship FPU18/05371, and Grants PID2019-104381 GB-I00, JCCM SBPLY/17/180501/000262, and UMA18FEDERJA060, respectively. Funding for open access charge: Universidad de Málaga /CBUA

Novel molecularly imprinted impedimetric biosensor based on polypyrrole and decorated graphene oxide for the routine monitoring of Lysozyme

In this work, a novel molecularly imprinted polymer based on polypyrrole (PPy) and decorated graphene oxide (GO@Fe3O4) was developed for the sensitive detection of lysozyme (LYS). The synthesized material (MIPPy/GO@Fe3O4) was electrodeposited with LYS as a template on gold microelectrodes. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to confirm the adequate preparation of GO@Fe3O4, and the characterization of the resulting microsensors was carried out with the following analytical techniques: electrochemical impedance spectrometry (EIS), FT-IR analysis and scanning electron microscopy (SEM). An equivalent circuit was suggested to quantitatively analyse each component of the sensor system. EIS was also used for the determination of LYS in a wide linear range from 1 to 1 105 pg/mL, presenting good precision (RSD ≈ 10%, n = 5) and low limits of detection and quantification (LOD = 0.009 pg/mL and LOQ = 0.9 pg/mL, respectively). Meanwhile, the microsensor showed a high sensitivity, a good selectivity and reproducibility. The construction process was relatively simple, and provided a rapid and economical method for the routine monitoring of LYS. The microsensor was successfully applied for the detection of this protein in fresh chicken-egg white sample and commercial drug.Campus de Excelencia Internacional Andalucía Tech. Beca FPU18/05371 Proyecto de la Junta de Andalucía UMA18FEDERJA06

Magnetic graphene oxide as a valuable material for the speciation of trace elements

Magnetic solid phase extraction (MSPE) has been explored for the application in preconcentration processes to achieve highly sensible analytical methods. Attending to the different magnetic adsorbent materials used in this field, functionalized magnetic graphene oxide (MGO) has proven to be effective for selective analysis and speciation of metals, metalloids, and derivatives in combination with several analytical techniques. Despite the increasing number of articles on speciation of trace elements using functionalized MGO as solid phase adsorbent, there are no dedicated reviews that cover the application of this novel nanomaterial, being this work pioneer in this area. This article provides a comprehensive review of the relevant literature related to the speciation of Al, Cr, As, Se, Ag, Cd, Hg, Tl and Pb, with special focus on species determined, toxicity, MGO functionalization, analytical performance, and applications, mainly to environmental and food samples. Finally, future challenges and trends related to this topic are shown.This work has been partially supported by the University of Malaga (I Plan Propio de Investigación y Transferencia, Proyecto Puente UMA and fellowship A.2.-2021 predoctoral contracts), FEDER funds, Junta de Andalucia, Project UMA18-FEDERJA-060 and the Spanish Ministerio de Ciencia y Tecnologia (fellowship FPU18/05371). Funding for open access charge: Universidad de Málaga / CBUA

Semiautomatic method for the ultra-trace arsenic speciation in environmental and biological samples via magnetic solid phase extraction prior to HPLC-ICP-MS determination

A novel magnetic functionalized material based on graphene oxide and magnetic nanoparticles (MGO) was used to develop a magnetic solid phase extraction method (MSPE) to enrich both, inorganic and organic arsenic species in environmental waters and biological samples. An automatic flow injection (FI) system was used to preconcentrate the arsenic species simultaneously, while the ultra-trace separation and determination of arsenobetaine (AsBet), cacodylate, AsIII and AsV species were achieved by high performance liquid chromatog raphy combined with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The sample was introduced in the FI system where the MSPE was performed, then 1 mL of eluent was collected in a chromatographic vial, which was introduced in the autosampler of HPLC-ICP-MS. Therefore, preconcentration and separation/deter mination processes were automatic and conducted separately. To the best of our knowledge, this is the first method combining an automatic MSPE with HPLC-ICP-MS for arsenic speciation, using a magnetic nanomaterial based on MGO for automatic MSPE. Under the optimized conditions, the LODs for the arsenic species were 3.8 ng L− 1 AsBet, 0.5 ng L− 1 cacodylate, 1.1 ng L− 1 AsIII and 0.2 ng L− 1 AsV with RSDs <5%. The developed method was validated by analyzing Certified Reference Materials for total As concentration (fortified lake water TMDA 64.3 and seawater CASS-6 NRC) and also by recovery analysis of the arsenic species in urine, well-water and seawater samples collected in Malaga. ´ The developed method has shown promise for routine monitoring of arsenic species in environmental waters and biological fluids.This work has been partially supported by the University of Malaga (Proyecto Puente UMA), FEDER funds, Junta de Andalucia, Project UMA18FEDERJA060 and the Spanish Ministerio de Ciencia y Tecnologia (fellowship FPU18/05371). Funding for open access charge: Universidad de Málaga / CBU

Phosphorus removal and recycled from tertiary effluent in sewage treatment plant using graphene modified with magnetic nanoparticles (M@GO).

Phosphorus is employed in detergents, as fertilizers in agriculture, etc. As a nutrient for plants, too much phosphorus can cause increased growth of algae and large aquatic plants, which can result in decreased levels of dissolved oxygen– a process called eutrophication. On the other hand, P is a relatively limited resource, considered by the European Union as a strategic interest material. Thus, the removal and recycled of P from the sewage treatment plants is of great interest to the society. In this work, a new patented magnetic graphene oxide (M@GO) for the removal of phosphorus from wastewater is studied. The main technical advantage of this solid adsorbent is its easy separation from the treated water by applying a magnetic field. The key factors affecting the sorption and elution efficiency are studied. The thermodynamic adsorption model that provides a best fit was the Langmuir isotherm. The mass transfer kinetic model indicates that the mass transfer of P between the bulk liquid and the solid surface is not the rate-limiting step of the adsorption process. The P adsorption on M@GO was demonstrated by TEM, XPS, FTIR. After the adsorption, an ammonia aqueous solution has provided to be the best eluent to recover the phosphorus from the solid adsorbent, as ammonium phosphate, with recovery yields above 90%. The results of this work have driven to the design of a new magnetic reactor for the treatment of waste water. Acknowledgements The authors thank to Spanish Ministerio de Ciencia e Innovación, Project PID2021-126794OB and the II Plan Propio UMA.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Simultaneous preconcentration and determination of trace metals (V, Ni, Ti, and Ga) in environmental samples by high resolution continuum source electrothermal atomic absorption spectrometry.

In this work is presented a simple, sensitive, low-cost method for direct and simultaneous determination of V, Ti, Ni and Ga by electrothermal atomic absorption spectrometer (ETAAS) in aqueous environmental samples (tap and seawater samples). The system is based on the retention of the analyte on a novel adsorbent material based on the coupling of magnetic nanoparticles (MNPs) and graphene oxide (GO) functionalised with methylthiosalicylate (MTS) that provides selectivity to interact with transition metals in solution, M@GO -MTS. The detection limits achieved with the method were 0.9 μg L-1 for Ti, 0.6 μg L-1 for V, 0.04 μg L-1 for Ga, 0.75 μg L-1 for Ni. The accuracy of the proposed method was demonstrated by analysing two certified reference materials and by determining the analyte content in spiked environmental water samples. The results obtained using this method were in good agreement with the certified values of the standard reference materials and the recoveries for the spiked tap water and seawater samples were between 90% to 120%.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Development of an on-line MSPE-ICP-OES method for the preconcentration and speciation of Cr(III)/Cr(VI) in aqueous samples

SHOTGUN PRESENTATIONIn this work, a new double-reactor method for the analysis and speciation of trace amounts of Cr(III)/Cr(VI) ions in environmental samples has been developed combining on-line magnetic solid phase extraction (MSPE) with inductively coupled plasma optical emission spectrometry (ICP OES). For the preconcentration and speciation of Cr, a new magnetic graphene oxide (MGO) functionalized with p-sulfanilic acid has been syhthesized. This material presents good capacity of adsorption towards Cr(III) and Cr(VI) species. The FI manifold used for on-line preconcentration and elution is shown in Fig.1. The eight-port valve (V) was changed from position A-B, and vice versa allowing the load of sample of the two reactors (R1 and R2) followed of the elution of Cr(VI) with NH3 3.2 % in R1 and total Cr with HNO3 2.3 % in R2 to ICP-OES. Subtracting the signal of Cr (VI) to the signal of Cr(III)+Cr(VI), both ions can be determined. Moreover, several flow and chemical variables were optimized by two multivariate central composite designs (CCD). The optimized method offers good sensitivity and precision. The accuracy of the proposed method was verified using certified reference materials. The obtained results were in good agreement with the certified values and high recoveries were achieved for the spiked samples. Thus, the new adsorbent has demonstrated to be useful for the preconcentration and speciation of Cr(III)/Cr(VI).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Fondos FEDER y Junta de Andalucía Proyecto UMA18-FEDERJA-060. Plan Propio. Proyecto Puente. Universidad de Málag

Using Flipped classroom at University to improve the chemistry learning.

The main objective of this paper was to improve the learning of Chemistry subject using Flipped classroom, because it makes class time more engaging. The lecture portion of General Chemistry courses in engineers degrees have been pushed outside the classroom using pre recording technology and steaming delivery of content, to make classes more interactive and participative. The Flipped classroom model has become one of the main topics in the higher education space in recent years thanks to improvements in technology. This year, the Flipped classroom model with the chemistry students at Malaga State University has been begun experimenting with. Statistical significance of the data has shown, and proved with, that implementing the Flipped classroom model could not only benefit professors, but it could also help us adapt the classes to the various learning styles that exist among the students. The study shows the results of surveys about student attitudes towards aspects of flipping the classroom.I Plan Propio Integral de Docencia, Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Determination of mercury in sea waters by magnetic dispersive solid phase extraction prior to quantitation by FI-CV-GFAAS

Shotgun PresentationMercury is a non-essential trace element that is toxic to humans due to the bioaccumulation effect. In this work, a shell structured Fe3O4@graphene oxide nanospheres were used to develop a magnetic dispersive solid phase extraction (MDSPE) method for the extraction and preconcentration of ultra-trace amounts of Hg(II). After first enrichment, a second online preconcentration by cold vapor generation was conducted, followed by the determination of the analyte by graphite furnace atomic absorption spectrometry (CV-GFAAS). The influences of several analytical parameters were optimized for MDSPE and CV-GFAAS. Under the optimized conditions, %RSD, detection limit and determination limit were 2.9%, 0.25 ng·L-1 and 4.9 ng·L-1 , respectively. Thanks to the 500 μL loop, a high preconcentration factor can be achieved even with low sample volume. For example, 5 mL of sample would be preconcentrated 10 times. Moreover, this method is suitable for high sample volume, resulting in a preconcentration factor >250. The accuracy of the proposed method was verified using a certified reference material (mussel tissue NIST 2976) and by determining the analyte content in spiked sea waters and tap water samples collected from Málaga and Cádiz (Spain). The determined values were in good agreement with the certified values and the recoveries for the spiked samples were close to 100% in all cases. The results showed the proposed method is simple, rapid, environmentally friendly and sensitive enough for the accurate determination of mercury.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech Fondos Feder y Junta de Andalucía Proyecto UMA18-FEDERJA-060 Plan Propio, Proyecto Puente, Universidad de Málag