Dispersion of multi-walled carbon nanotubes in [BMIM]PF 6 for electrochemical sensing of acetaminophen

The influence of functionalized multi-walled carbon nanotubes (fMWCNT) in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) in different ratios was investigated on the acetaminophen (ACOP) electrochemical determination. The electrochemical behavior of the ACOP exhibited a pair of well-defined redox peaks, suggesting that the reversibility of ACOP was significantly improved in comparison to irreversible oxidation peak on bare GCE. The redox process was controlled by adsorption, involves two electrons and the value of apparent rate constant (ks) was equal to 14.7 s-1 ± 3.6 s-1. The analytical curves were obtained for concentrations of ACOP ranging from 0.3 to 3.0 μmol L-1. The values of the detection limit were calculated from SWV and found to be 6.73 × 10-8 mol L-1. The proposed electrochemical sensor exhibited good stability and reproducibility and was applied for ACOP determination in tablets (Tylenol® and Tylenol®DC) with satisfactory results.The authors gratefully acknowledge funding provided by the following Brazilian agencies: CNPq-INCT (Proc. 573925/2008-9 and 573548/2008-0), CAPES/Funcap (2133/2012/Proc. 23038.007973/2012-90), CNPq-PVE (Proc. 400223/2014-7 and 303596/2014-7), PRONEX/FUNCAP (Proc. PR2-0101-00030.01.00/15) and CNPq (Proc. 302801/2014-6). R.N. Gomes thanks CAPES and C.P. Sousa thanks CAPES-PNPD for their grants. The authors also are grateful to the Central Analítica-UFC/CT-INFRA/MCTI-SISNANO/Pró-Equipamentos CAPES for technical support and Prof. Pierre Basílio Almeida Fechine and MsC. Davino Machado Andrade Neto for Zeta potential analysis.info:eu-repo/semantics/publishedVersio

(Bio)Sensing Strategies Based on Ionic Liquid-Functionalized Carbon Nanocomposites for Pharmaceuticals: Towards Greener Electrochemical Tools

The interaction of carbon-based nanomaterials and ionic liquids (ILs) has been thoroughly exploited for diverse electroanalytical solutions since the first report in 2003. This combination, either through covalent or non-covalent functionalization, takes advantage of the unique characteristics inherent to each material, resulting in synergistic effects that are conferred to the electrochemical (bio)sensing system. From one side, carbon nanomaterials offer miniaturization capacity with enhanced electron transfer rates at a reduced cost, whereas from the other side, ILs contribute as ecological dispersing media for the nanostructures, improving conductivity and biocompatibility. The present review focuses on the use of this interesting type of nanocomposites for the development of (bio)sensors specifically for pharmaceutical detection, with emphasis on the analytical (bio)sensing features. The literature search displayed the conjugation of more than 20 different ILs and several carbon nanomaterials (MWCNT, SWCNT, graphene, carbon nanofibers, fullerene, and carbon quantum dots, among others) that were applied for a large set (about 60) of pharmaceutical compounds. This great variability causes a straightforward comparison between sensors to be a challenging task. Undoubtedly, electrochemical sensors based on the conjugation of carbon nanomaterials with ILs can potentially be established as sustainable analytical tools and viable alternatives to more traditional methods, especially concerning in situ environmental analysisThis work was financed by FEDER—Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020—Operacional Programme for Competitiveness and Internationalization (POCI), and by Portuguese funds through FCT—Fundação para a Ciência e a Tecnologia in the framework of the project POCI-01-0145-FEDER-029547—PTDC/ASP-PES/29547/2017. This work received support by UIDB/50006/2020, UIDP/50006/ 2020 and LA/P/0008/2020 by the Fundação para a Ciência e a Tecnologia (FCT), Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) through national funds. T.M.B.F. Oliveira thanks the Brazilian agencies CNPq (Proc. 420261/2018-4 and 308108/2020-5) and FUNCAP (Proc. BP4-0172-00111.01.00/20) for their financial support, and he is grateful to UFCA and CAPES (Finance code 001) for supporting his investigations. F.W.P. Ribeiro thanks all support provided by the UFCA’s Pro-Rectory of Research and Innovation and the funding provided by FUNCAP-BPI (Proc. BP4-0172-00150.01.00/20) and CNPq (Proc. 406135/2018-5). P. de Lima-Neto thanks the financial support received from CNPq projects 408626/2018-6 and 304152/2018-8 and FUNCAP project FCT-00141-00011.01.00/18. A. N. Correia thanks the financial support received from CNPq projects: 305136/2018-6 and 405596/2018-9info:eu-repo/semantics/publishedVersio

Influence of recirculation rate on the performance of a combined anaerobic-aerobic reactor applied to the removal of carbon and nitrogen from poultry slaughterhouse wastewater

The objective of this study was to evaluate a combined anaerobic-aerobic upflow fixed-bed reactor with liquid phase recirculation for the removal of nitrogen and organic matter from poultry slaughterhouse wastewater. The reactor performance was evaluated with a hydraulic retention time (HRT) of 11 h and three different recirculation rates (R=0.5; 1 and 2). The highest nitrogen removal efficiency value was obtained with an HRT of 11 h (6.8 h in the anaerobic zone and 4.2 h in the aerobic zone) and a recirculation rate of 2. In this condition, the total nitrogen removal efficiency was 69%,  with effluent concentrations of 6 mg NH4+ L-1 and 12 mg NO3- L-1. For all tested conditions, there was good chemical oxygen demand (COD) removal, with efficiency above 95%. The effect of dilution and the favoring of mass transfer caused by the increase in the recirculation rate positively influenced reactor performance.Key words: Anaerobic degradation, nitrification, denitrification, combined reactor

Chitosan-magnetite nanocomposite as a sensing platform to bendiocarb determination

A novel platform for carbamate-based pesticide quantification using a chitosan/magnetic iron oxide (Chit-Fe3O4) nanocomposite as a glassy carbon electrode (GCE) modifier is shown for an analytical methodology for determination of bendiocarb (BND). The BND oxidation signal using GCE/Chit-Fe3O4 compared with bare GCE was catalyzed, showing a 37.5% of current increase with the peak potential towards less positive values, showing method's increased sensitivity and selectivity. Using square-wave voltammetry (SWV), calibration curves for BND determination were obtained (n = 3), and calculated detection and quantification limits values were 2.09 × 10-6 mol L-1 (466.99 ppb) and 6.97 × 10-6 mol L-1 (1555.91 ppb), respectively. The proposed electroanalytical methodology was successfully applied for BND quantification in natural raw waters without any sample pretreatment, proving that the GCE/Chit-Fe3O4 modified electrode showed great potential for BND determination in complex samples. ᅟ Graphical abstract.The authors gratefully acknowledge the funding provided by the following Brazilian agencies: CNPq-INCT (proc. 573925/2008-9 and 573548/2008-0), CAPES/Funcap (2133/2012/proc. 23038.007973/2012-90 and PNE-0112-00048.01.00/16), CNPq (proc. 400223/2014-7, 303596/2014-7, 302801/2014-6 and 408790/2016-4), PRONEM/FUNCAP/CNPq (PNE-0112-00048.01.00/16) and PRONEX/Funcap (proc. PR2-0101-00030.01.00/15). The Fundação para a Ciência e a Tecnologia (FCT) and the FEDER, under Programme PT2020 (Project UID/QUI/50006/2013) and the project Qualidade e Segurança Alimentar- uma abordagem (nano) tecnológica (NORTE-01-0145-FEDER-000011) are also acknowledged for the financial funding. R.M.F. and J.C.D. acknowledge the financial support by Fondecyt 3170240 and Basal Program for Centers of Excellence, Grant FB0807 CEDENNA, CONICYT. C.P.S. thanks CAPES-PNPD for her grant.info:eu-repo/semantics/publishedVersio

Sensitive bi-enzymatic biosensor based on polyphenoloxidases–gold nanoparticles–chitosan hybrid film–graphene doped carbon paste electrode for carbamates detection

A bi-enzymatic biosensor (LACC–TYR–AuNPs–CS/GPE) for carbamates was prepared in a single step by electrodeposition of a hybrid film onto a graphene doped carbon paste electrode (GPE). Graphene and the gold nanoparticles (AuNPs) were morphologically characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, dynamic light scattering and laser Doppler velocimetry. The electrodeposited hybrid film was composed of laccase (LACC), tyrosinase (TYR) and AuNPs entrapped in a chitosan (CS) polymeric matrix. Experimental parameters, namely graphene redox state, AuNPs:CS ratio, enzymes concentration, pH and inhibition time were evaluated. LACC–TYR–AuNPs–CS/GPE exhibited an improved Michaelis–Menten kinetic constant (26.9 ± 0.5 M) when compared with LACC–AuNPs–CS/GPE (37.8 ± 0.2 M) and TYR–AuNPs–CS/GPE (52.3 ± 0.4 M). Using 4-aminophenol as substrate at pH 5.5, the device presented wide linear ranges, low detection limits (1.68×10− 9 ± 1.18×10− 10 – 2.15×10− 7 ± 3.41×10− 9 M), high accuracy, sensitivity (1.13×106 ± 8.11×104 – 2.19×108 ± 2.51×107 %inhibition M− 1), repeatability (1.2–5.8% RSD), reproducibility (3.2–6.5% RSD) and stability (ca. twenty days) to determine carbaryl, formetanate hydrochloride, propoxur and ziram in citrus fruits based on their inhibitory capacity on the polyphenoloxidases activity. Recoveries at two fortified levels ranged from 93.8 ± 0.3% (lemon) to 97.8 ± 0.3% (orange). Glucose, citric acid and ascorbic acid do not interfere significantly in the electroanalysis. The proposed electroanalytical procedure can be a promising tool for food safety control

Electroanalysis of Imidacloprid Insecticide in River Waters Using Functionalized Multi-Walled Carbon Nanotubes Modified Glassy Carbon Electrode

In this work, a functionalized multi-walled carbon nanotubes modified glassy carbon electrode (GCE/MWCNT-f) was optimized for the direct determination of imidacloprid (IMC) insecticide in river water. The functionalized material was characterized by infrared spectroscopy with Fourier transform (FTIR) and the modified electrode by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Results revealed that the GCE/MWCNT-f effectively increased the response toward IMC reduction by enhancing the reduction peak current and decreasing the peak potential in comparison with the bare electrode. After optimizing the electroanalytical conditions, the GCE/MWCNT-f showed a linear voltammetric response at concentration ranging from 2.40 × 10−7 to 3.50 × 10−6 mol L−1, with detection and quantification limits of 4.15 × 10−7 mol L−1 and 1.38 × 10−6 mol L−1, respectively. The recovery rate of IMC in spiked river water samples varied from 90–95%. Thus, this sensor can be a promising tool for the analysis and monitoring of IMC in complex environmental matrices.info:eu-repo/semantics/publishedVersio