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

Strategies for antidepressants extraction from biological specimens using nanomaterials for analytical purposes: A review

Accurate and precise monitoring of antidepressant drugs represents a crucial step for the adequate and personalized treatment of several psychological disorders such as depression, which nowadays represent a social, economic and health major concern. Several chemical, electrochemical, and biological methods have been traditionally developed for the extraction and detection of antidepressants, even though several restrictions such as post-treatment required, elevate costs and limited efficiency. Nanotechnology is a field with a tremendous growth observed in the last two decades, especially regarding their many biological applications, such as antibacterial or as biosensors, as well as in many different applications related to medicine. Lately, nanotechnology has emerged as a promising substitute for the extraction of antidepressants instead of traditional techniques, as nanomaterials can be efficiently used as sorbents due to their small size and their high specific surface area which enhance their high reactivity. In this review article, we provide a general overview on the use of different nanomaterials for the extraction of antidepressants from biological specimens and discuss not only the advantages but also the major limitations of using such nanomaterials. Potential alternatives to overcome these drawbacks are discussed as well

Effect of chlorine group position on adsorption behavior and corrosion inhibition of Chlorobenzylideneamino-5-methyl-2, 4-dihydro-1, 2, 4-triazole-3-thione Schiff bases: Experimental study

The corrosion inhibition and adsorption of 4-(n-Chlorobenzylideneamino)-5-methyl-2,4-dihydro-1,2,4-triazole-3-thione (n-CBAT) Schiff bases has been investigated on steel electrode in 1.0 M HCl by using weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy (EIS) methods. The results show that all n-CBAT are good inhibitors, and inhibition efficiency follows the order:4-CBAT <3-CBAT <2-CBAT. Polarization curves reveal that all studied inhibitors are mixed type. The adsorption of each inhibitor on mild steel surface obeys Langmuir adsorption isotherm. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The effect of temperature on the corrosion behavior with addition of 1×10−3Mof n-CBAT added was studied in the temperature range 30–60◦C. The thermodynamic parameters activation were determined and discussed

Electrochemically-based hybrid oxidative technologies for the treatment of micropollutants in drinking water

Simultaneous degradation of sulfadiazine, naproxen, diclofenac, ketoprofen and ibuprofen from drinking water was investigated by different technologies including photolysis, electrooxidation, photo-electrooxidation, zero-valent iron and their combinations. All oxidation technologies were very effective for the degradation of all drugs under anoxic conditions and the efficiency decreased under oxic conditions. Results also revealed that all drugs can be photochemically degraded by direct reactions, being ketoprofen and diclofenac completely degraded in only 10 min. Oxidizability with electrooxidation decreases in the sequence sulfadiazine > naproxen > diclofenac > ketoprofen > ibuprofen. Antagonistic effect was observed when photolysis was coupled to electrooxidation for all drugs under anoxic and oxic conditions, except for ibuprofen under O2 bubbling. On the other hand, synergistic effect was observed for ZVI + photolysis, ZVI + electrooxidation for ketoprofen and ibuprofen drugs and ZVI + Photo-electrooxidation for ibuprofen removal. Photo-electrooxidation coupled to ZVI under nitrogen bubbling was found to be the most efficient process.La degradación simultánea de sulfadiazina, naproxeno, diclofenaco, ketoprofeno e ibuprofeno del agua potable se investigó mediante diferentes tecnologías que incluyen fotólisis, electrooxidación, fotoelectrooxidación, hierro de valencia cero y sus combinaciones. Todas las tecnologías de oxidación fueron muy efectivas para la degradación de todos los fármacos en condiciones anóxicas y la eficiencia disminuyó en condiciones óxicas. Los resultados también revelaron que todos los fármacos pueden degradarse fotoquímicamente por reacciones directas, siendo el ketoprofeno y el diclofenaco completamente degradados en solo 10 min. La oxidabilidad con electrooxidación disminuye en la secuencia sulfadiazina> naproxeno> diclofenaco> ketoprofeno> ibuprofeno. Se observó un efecto antagonista cuando la fotólisis se acopló a la electrooxidación para todos los fármacos en condiciones anóxicas y óxicas.2 burbujeantes. Por otro lado, se observó un efecto sinérgico para la fotólisis de ZVI +, la electrooxidación de ZVI + para los fármacos ketoprofeno e ibuprofeno y la fotoelectrooxidación de ZVI + para la eliminación de ibuprofeno. Se encontró que la fotoelectrooxidación acoplada a ZVI bajo burbujeo de nitrógeno es el proceso más eficiente

SERS-Based Methodology for the Quantification of Ultratrace Graphene Oxide in Water Samples

The extensive use of graphene materials in real-world applications has increased their potential release into the environment. To evaluate their possible health and ecological risks, there is a need for analytical methods that can quantify these materials at very low concentrations in environmental media such as water. In this work, a simple, reproducible, and sensitive method to detect graphene oxide (GO) in water samples using the surface-enhanced Raman spectroscopy (SERS) technique is presented. The Raman signal of graphene is enhanced when deposited on a substrate of gold nanoparticles (AuNPs), thus enabling its determination at low concentrations with no need for any preconcentration step. The practical limit of quantification achieved with the proposed method was 0.1 ng mL–1, which is lower than the predicted concentrations for graphene in effluent water reported to date. The optimized procedure has been successively applied to the determination of ultratraces of GO in water samples

Rapid determination of malondialdehyde in serum samples using a porphyrin-functionalized magnetic graphene oxide electrochemical sensor

An electrochemical sensor based on a screen-printed carbon electrode (SPCE) modified with porphyrin-functionalized magnetic graphene oxide (TCPP-MGO) was developed for the sensitive and selective determination of malondialdehyde (MDA), an important biomarker of oxidative damage, in serum samples. The coupling of TCPP 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 TCPPMGO surface. The electron-transfer capability in the SPCE was improved through derivatization of MDA with diaminonaphthalene (DAN) (MDA-DAN). TCPP-MGO-SPCEs have been employed to monitor the differential pulse voltammetry (DVP) levels of the whole 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) with a correlation coefficient of 0.9996. The practical limit of quantification (P-LOQ) of the analyte was 0.010 μM, and the relative standard deviation (RSD) was 6.87% for 30 μM MDA concentration. Finally, the developed electrochemical sensor has demonstrated to be adequate for bioanalytical applications, presenting an excellent analytical performance for the routine monitoring of MDA in serum samples.Financial support from the Spanish Ministry of Science and Innovation (PID2019-104381 GB-I00), Junta de Comunidades de Castilla-La Mancha (SBPLY/21/180501/000188), and University of Castilla-La Mancha (2020-GRIN-28882) is gratefully acknowledged. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.Peer reviewe

LC-MS determination of catecholamines and related metabolites in red deer urine and hair extracted using magnetic multi-walled carbon nanotube poly(styrene-co-divinylbenzene) composite

A novel analytical methodology for the extraction and determination of catecholamines (dopamine, epinephrine and norepinephrine) and their metabolites DL-3,4-dihydroxyphenyl glycol and DL-3,4-dihydroxymandelic acid by LC-MS is developed and validated for its application to human and animal urine and hair samples. The method is based on the preliminary extraction of the analytes by a magnetic multi-walled carbon nanotube poly(styrene-co-divinylbenzene) composite. This is followed by a 90%. Accuracy values comprised the range 79.5–109.5% when the analytes were extracted from deer urine samples using the selected MMWCNT-poly(STY-DVB) sorbent. This methodology was applied to real red deer urine and hair samples, and concentrations within range from 0.05 to 0.5 µg mL−1 for norepinephrine and from 1.0to 44.5 µg mL−1 for its metabolite 3,4-dihydroxyphenyl glycol were calculated. Analyses of red deer hair resulted in high amounts of 3,4-dihydroxyphenyl glycol (0.9–266.9 µg mL−1

Design and Adaptation of an Interface for Commercial Capillary ElectrophoresisEvaporative Light Scattering Detection Coupling

In this technical note, an interface for coupling commercially available capillary electrophoresis (CE) equipment to an evaporative light scattering detector (ELSD) is described. The nebulization process was identified as the most critical parameter for performing the reliable coupling between both pieces of equipment. Therefore, appropriate modifications in the nebulization chamber and in the conventional nebulizer were brought to make ELSD fully compatible with CE. The impact of the customized interface on CE separation and detection was evaluated in terms of resolution and sensitivity. ELSD can be considered as an attractive alternative to other CE detection systems (e.g., UV–vis, fluorescence, electrochemical detection, or even MS detection), particularly those in which derivatization is needed. This advantage is due to the versatility and the quasi-universality of ELSD. Thus, sensitive and fast separations of several compounds were performed using this CE–ELSD customized arrangement, which opens up an interesting analytical potential for the determination of compounds not presenting sensitive UV–vis chormophore, fluorophore, or electroactive groups. Carbohydrates were selected in this work to demonstrate the applicability of CE–ELSD coupling