Search

The combination of amoxicillin (AMX) and clavulanic acid (CLA) is one of the most widely used antibiotic medicines in the world. This paper describes a novel electrochemical method for the fast sequential determination of AMX and CLA using batch injection analysis with amperometric detection (BIA‐AD) and boron‐doped diamond (BDD) as the working electrode. In the proposed strategy, AMX was selectively detected at +1.3 V and both compounds (AMX+CLA) at +1.8 V. The oxidation current from CLA was accessed by subtracting the currents detected at both potential pulses (i+1.8 V–i+1.3V) and using a simple correction factor. The developed method proved to be simple, cost‐effective, precise (RSD<1.3 %, n=10), rapid (>200 injection h−1), required simple sample preparation steps (dissolution and dilution only) and can be used in laboratories with minimal infrastructure (portable characteristics). The limits of detection were 0.31 (0.13) and 1.99 (0.47) μmol L−1 (mg L−1) for AMX and CLA, respectively. The results obtained by the proposed BIA‐AD method were comparable to those obtained by capillary electrophorese (95 % confidence level). [ABSTRACT FROM AUTHOR]

Coupling of UV-C irradiation to different peroxides (H 2 O 2 , S 2 O 8 2- and HSO 5 - ) has great potential to degrade persistent organic compounds due to the formation of HO • or SO 4 •- species. However, an in-depth comparison between the performance of different UV-C/peroxide processes as a function of (i) target compound degradation, (ii) generated transformation products and (iii) lethal/sub lethal toxicity effects has not yet been performed. To this end a comparison study was carried out to evaluate the effectiveness of different UV-C/peroxide processes using the herbicide tebuthiuron (100 or 500 μg L -1 ) as a model pollutant. TBH degradation experiments were performed at lab-scale in real municipal wastewater treatment plant effluent and distilled water. Faster degradation occurred by increasing peroxide concentration from 735 to 2206 μmol L -1 in the municipal wastewater treatment plant effluent, mainly for S 2 O 8 2- . Experiments performed in the presence of peroxide trapping agents - HO • and SO 4 •- (methoxibenzene) or HO • (2-propanol) - revealed that oxidation in the UV-C/S 2 O 8 2- system occurs mainly through SO 4 •- . Lower toxicity for the MWWTP effluent was obtained after oxidative treatments using hydrogen peroxide or monopersulfate as oxidants which react mainly through HO • radicals. Two mechanistic pathways were proposed for tebuthiuron degradation: (i) hydrogen abstraction by HO • (H 2 O 2 and HSO 5 - ) and (ii) electron transfer by SO 4 •- (S 2 O 8 2- ). In addition, one unprecedented transformation product was identified. In conclusion, results emphasize the relevance of comparing the degradation of toxic compounds in the presence of different peroxide sources and matrices and simultaneouly evaluating responses chemical and biological endpoints., Competing Interests: Declaration of competing interest There are no conflicts to declare., (Copyright © 2022 Elsevier B.V. All rights reserved.)

As the presence of antibiotics in environmental waters enhances antimicrobial resistance, photolysis and heterogeneous photocatalysis of chloramphenicol (CAP) were evaluated in deionized water (DW) and in sewage treatment plant (STP) effluent under black light and solar irradiation. Processes were compared in terms of CAP degradation, reaction kinetics, and electrical energy per order, as well as regarding theoretical toxicity, biodegradability, carcinogenicity, and mutagenicity of transformation products (TPs). Rate constants obtained under photolysis (0.008 min -1 ) and heterogeneous photocatalysis (0.18 min -1 ) only differed in DW. This is due to the generation of photo-active reactive oxygen species (HO · and HO 2 ·- /O 2 ·- ) under photolysis in STP effluent, as verified by experiments in the presence of 2-propanol and chloroform. Natural organic matter and HCO 3 - were the main responsible for reducing CAP degradation in STP effluent. Fifteen TPs were identified during both processes in DW, 13 of which are unprecedented. TPs were formed mainly via HO · preferential attack on the aromatic ring and on the α-carbon, and some of them were classified as persistent and toxic, genotoxic, or carcinogenic by Toxtree software. Results confirm that solar photocatalysis is less costly than to photocatalysis under black light for wastewater treatment.

Banisteriopsis argyrophylla belongs to the Malpighiaceae family, which is a species from Cerrado, also known as "cipó-prata" or "cipó-folha-de-prata." Several species of this family present biological potential. This work reports the chemical identification of the ethanol extract (EE) and its fractions from B. argyrophylla leaves and shows the analysis of the antioxidant activity and inhibitory effects on activities of α-amylase, α-glucosidase and lipase, and non-enzymatic glycation. The ethyl acetate fraction (EAF) and n-butanol fraction (BF) showed antioxidant activity, with IC 50 values of 4.1 ± 0.1 and 4.8 ± 0.1 μg mL -1 , respectively, by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, and IC 50 values of 6046.3 ± 174.2 and 6264.2 ± 32.2 µmol Trolox eq g -1 by the oxygen radical absorbance capacity (ORAC) method. Furthermore, the DPPH method with these fractions presented electroactive species with antioxidant potential, as shown by the differential pulse voltammetry (DPV) method. The inhibitory effects of the EAF and BF were demonstrated by the following results: IC 50 of 5.1 ± 0.3 and 2.5 ± 0.2 μg mL -1 for α-amylase, IC 50 of 1093.5 ± 26.0 and 1250.8 ± 21.9 μg mL -1 for α-glucosidase, IC 50 of 8.3 ± 4.1 and 4.4 ± 1.0 μg mL -1 for lipase, and IC 50 of 1.3 ± 0.1 and 0.9 ± 0.1 μg mL -1 for glycation. Some bioactive compounds were identified by (-)-ESI-MS/MS, such as catechin, procyanidins, glycosylated flavonoids, kaempferol, and megastigmane glucosides. The antidiabetic activity of B.argyrophylla has been reported for the first time., (Copyright © 2020 Elsevier Inc. All rights reserved.)

This study presents the degradation of fipronil in sewage treatment plant (STP) effluent by photo-Fenton at near neutral pH (pH 6.0) using Fe 3+ /Citrate complex. 83% of fipronil degradation was reached using a molar iron/citrate ratio of 1:3 (192 μmol L -1 of Fe 3+ /576 μmol L -1 of citrate). Photo-Fenton reduced the toxicity of treated solutions as according to the survival of Drosophila melanogaster exposed to non-treated and treated samples. Control experiments performed in distilled water using 32 μmol L -1 of Fe 3+ /96 μmol L -1 of citrate achieved 98% of fipronil degradation within 100 kJ m -2 (UV-A radiation, k = 30 × 10 -3  kJ -1  m 2 and t 1/2  = 23 kJ m -2 ), thus indicating that fipronil degradation is impaired by natural organic matter and inorganic ions present in STP effluent. Degradation was faster under solar radiation, as the same efficiency (98%) was obtained after 75 kJ m -2 (k = 63 × 10 -3  kJ -1  m 2 and t 1/2  = 11 kJ m -2 ). In addition, pathways of fipronil degradation using Fe 3+ /Citrate under solar and UV-A radiation were investigated and transformation products proposed. Results revealed that the HO • attack occurred preferentially in the pyrazole ring. Eight transformation products were identified by UHPLC-Q-TOF-MS and four are unprecedented in the literature. Control experiments in distilled water demonstrated that toxicity reduction is related to fipronil degradation and that transformation products are less toxic than fipronil. Furthermore, toxicity of STP fortified with fipronil was reduced after photo-Fenton. These results demonstrate the feasibility of applying this process using Fe 3+ /Citrate complex for fipronil degradation in a real matrix., Competing Interests: Declaration of competing interest There are no conflicts to declare., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Midazolam (MID) is a sedative drug which can be added in beverage samples as drug-facilitated-sexual assault (date rape drug). This type of drug has short half-life in biological fluids (not detectable) which often prevents the correlation between drug abuse and crime. In this work, we described a simple and low-cost method for fast screening and selective determination of MID in beverage samples (vodka, whiskey and red wine). For the first time, the electrochemical oxidation of MID was used for this purpose. The oxidation mechanism was studied using electrochemical techniques (cyclic and square-wave voltammetry) and computational simulations (density functional theory calculations). Differential-pulse voltammetry, boron-doped diamond electrode (BDDE), and Britton-Robinson (BR) buffer (pH = 2) were selected as electrochemical analysis technique, working electrode and supporting electrolyte, respectively. Different linear response ranges (4-25 μmol L -1 with r = 0.9972; 1-10 μmol L -1 with r = 0.9951; 1-15 μmol L -1 with r = 0.9982) and limits of detection (0.46, 0.43 and 0.33 μmol L -1 ) were obtained for the analysis of vodka, whisky, and red wine solutions, respectively. The precision and accuracy were satisfactory considering the low relative standard deviation values (RSD < 6.3%, n = 15) and minimal sample matrix effects (recovery values between 87 and 103%)., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The feasibility of biodiesel effluent treatment combining coagulation-flocculation with a photolytic process was evaluated, being the photolytic process involving the irradiation of the effluent by UV-C, or by UV-C irradiation with simultaneous addition of H 2 O 2 (H 2 O 2 /UV-C). The coagulation-flocculation was performed at the natural pH of the effluent (pH 2.9) using different Fe 3+ salts (chloride, nitrate and sulfate) at different concentrations (0.25, 0.50 and 1.0 mmol L -1 ) of the counterions. The best results were achieved using 0.50 mmol L -1 Fe(NO 3 ) 3 . Following, the degradation of the organic load and toxicity reduction of the pre-treated effluent by UV-C irradiation was evaluated. The H 2 O 2 /UV-C process showed to be advantageous, mainly when multiple additions of H 2 O 2 were used during the course of the reaction. Additionally, the influence of the initial pH on the degradation was also evaluated. A high level of mineralization (94%) was achieved after 6 h of irradiation concomitantly with multiple additions of 2,000 mg L -1 H 2 O 2 , and with the effluent at the natural pH. Thus, using coagulation-flocculation followed by the H 2 O 2 /UV-C process, it was possible to achieve a favourable condition for reuse of the pre-treated effluent, since, in addition to the significant reduction of the organic load, the final DBO 5 (<120 mg L -1 ) and oils & fats (<50 mg L -1 ) are below the limits established by the Brazilian legislation. Furthermore, a reduction of 78% of acute toxicity to V. fischeri (from 89% to 20%) was reached. The results suggest, therefore, that this process is a viable option for treatment of this kind of effluent., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Annona crassiflora Mart., whose fruit is popularly known as araticum, is a member of the Annonaceae family found in the Brazilian Cerrado. Although this plant has several medicinal uses, its bioactive molecules are not fully understood. A bioguided assay was performed to identify the main bioactive compounds of A. crassiflora fruit peel from the ethanol extract fractions with antioxidant capacity and α-amylase, α-glucosidase and glycation inhibitory activities. Ethyl acetate and n-butanol fractions showed, respectively, higher antioxidant capacity (DPPH IC 50 1.5±0.1 and 0.8±0.1μgmL -1 , ORAC 3355±164 and 2714±79μmoltroloxeq/g, and FRAP 888±16 and 921±9μmoltroloxeq/g) and inhibitory activities against α-amylase (IC 50 4.5±0.8 and 1.7±0.3μgmL -1 ), α-glucosidase (IC 50 554.5±158.6 and 787.8±140.6μgmL -1 ) and glycation (IC 50 14.3±3.3 and 16.0±4.2μgmL -1 ), and lower cytotoxicity, compared to the other fractions and crude ethanol extract. The HPLC-ESI-MS/MS analysis identified various biomolecules known as potent antioxidants, such as chlorogenic acid, (epi)catechin, procyanidins, caffeoyl-hexosides, quercetin-glucosides and kaempferol. The fruit peel of A. crassiflora, a specie from Cerrado, the Brazilian Savanna, provided a source of antioxidant compounds with properties to block carbohydrate digestive enzymes and formation of glycation products. Thus, there is potential to use the by-products of araticum in order to identify and isolate phytochemicals for application in nutraceutical supplements, food additives and pharmaceuticals products., (Copyright © 2016 Elsevier Inc. All rights reserved.)

This work presents the potential application of organic-resistant screen-printed graphitic electrodes (SPGEs) for fuel analysis. The required analysis of the antioxidant 2,6-di-tert-butylphenol (2,6-DTBP) in biodiesel and jet fuel is demonstrated as a proof-of-concept. The screen-printing of graphite, Ag/AgCl and insulator inks on a polyester substrate (250 μm thickness) resulted in SPGEs highly compatible with liquid fuels. SPGEs were placed on a batch-injection analysis (BIA) cell, which was filled with a hydroethanolic solution containing 99% v/v ethanol and 0.1 mol L(-1) HClO4 (electrolyte). An electronic micropipette was connected to the cell to perform injections (100 μL) of sample or standard solutions. Over 200 injections can be injected continuously without replacing electrolyte and SPGE strip. Amperometric detection (+1.1 V vs. Ag/AgCl) of 2,6-DTBP provided fast (around 8 s) and precise (RSD = 0.7%, n = 12) determinations using an external calibration curve. The method was applied for the analysis of biodiesel and aviation jet fuel samples and comparable results with liquid and gas chromatographic analyses, typically required for biodiesel and jet fuel samples, were obtained. Hence, these SPGE strips are completely compatible with organic samples and their combination with the BIA cell shows great promise for routine and portable analysis of fuels and other organic liquid samples without requiring sophisticated sample treatments., (Copyright © 2016 Elsevier B.V. All rights reserved.)

This work proposes the application of batch-injection analysis with amperometric detection to determine the antioxidant capacity of real samples based on the measurement of DPPH radical consumption. The efficient concentration or EC50 value corresponds to the concentration of sample or standard required to scavenge 50% DPPH radicals. For the accurate determination of EC50, samples were incubated with DPPH radical for 1h because many polyphenolic compounds typically found in plants and responsible for the antioxidant activity exhibit slow kinetics. The BIA system with amperometric detection using a glassy-carbon electrode presented high precision (RSD = 0.7%, n = 12), low detection limit (1 μmol L(-1)) and selective detection of DPPH (free of interferences from antioxidants). These contributed to low detection limits for the antioxidant (0.015 and 0.19 μmol L(-1) for gallic acid and butylated hydroxytoluene, respectively). Moreover, BIA methods show great promise for portable analysis because battery-powered instrumentation (electronic micropipette and potentiostats) is commercially available., (Copyright © 2015 Elsevier Ltd. All rights reserved.)