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1.
Biochem Biophys Res Commun ; 530(1): 1-3, 2020 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-32828268

RESUMO

Alcohol-based disinfectant shortage is a serious concern in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Acidic electrolyzed water (EW) with a high concentration of free available chlorine (FAC) shows strong antimicrobial activity against bacteria, fungi, and viruses. Here, we assessed the SARS-CoV-2-inactivating efficacy of acidic EW for use as an alternative disinfectant. The quick virucidal effect of acidic EW depended on the concentrations of contained-FAC. The effect completely disappeared in acidic EW in which FAC was lost owing to long-time storage after generation. In addition, the virucidal activity increased proportionately with the volume of acidic EW mixed with the virus solution when the FAC concentration in EW was same. These findings suggest that the virucidal activity of acidic EW against SARS-CoV-2 depends on the amount of FAC contacting the virus.


Assuntos
Betacoronavirus/efeitos dos fármacos , Cloro/farmacologia , Desinfetantes/farmacologia , Desinfecção/métodos , Inativação de Vírus/efeitos dos fármacos , Ácidos/química , Ácidos/farmacologia , Antivirais/química , Antivirais/farmacologia , Betacoronavirus/fisiologia , Cloro/química , Infecções por Coronavirus/prevenção & controle , Infecções por Coronavirus/virologia , Desinfetantes/química , Eletrólise/métodos , Humanos , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Pneumonia Viral/virologia , Água/química , Água/farmacologia
2.
Chemosphere ; 260: 127579, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32679375

RESUMO

As important emerging contaminants, nonsteroidal anti-inflammatory drugs (NSAIDs) are the most intensively prescribed pharmaceuticals introduced to drinking water due to their incomplete removal in wastewater treatment. While concentrations of NSAIDs in drinking water are generally low, they have been attracting increasing concern as a result of their disinfection byproducts (DBPs) generated in drinking water disinfection. In this work, detection methods were set up for four representative indole-derivative NSAIDs (indomethacin, acemetacin, sulindac, and etodolac) using ultra performance liquid chromatography/electrospray ionization-triple quadruple mass spectrometry (UPLC/ESI-tqMS). ESI+ was better for detection of indomethacin and sulindac, whereas ESI- was suitable to detection of acemetacin and etodolac. With optimized MS parameters, the instrument detection and quantitation limits of the four indole derivatives were achieved to be 1.1-24.6 ng/L and 3.7-41.0 ng/L, respectively. During chlorination, indomethacin and acemetacin could undergo five major reaction types (chlorine substitution, hydrolysis, decarboxylation, C-C coupling, and C-N cleavage) to form a series of DBPs, among which 19 were proposed/identified with structures. Based on the revealed structures of DBPs, transformation pathways of indomethacin and acemetacin in chlorination were partially elucidated. Notably, individual and mixture toxicity of indomethacin and acemetacin before/after chlorination were evaluated using a well-established acute toxicity assessment and a Hep G2 cell cytotoxicity assay, respectively. Results showed that the predicted acute toxicity of a few chlorination DBPs were higher than their precursors; chlorination substantially enhanced the mixture cytotoxicity of indomethacin by over 10 times and slightly increased the mixture cytotoxicity of acemetacin.


Assuntos
Anti-Inflamatórios não Esteroides/análise , Anti-Inflamatórios não Esteroides/toxicidade , Desinfecção/métodos , Poluentes Químicos da Água/análise , Anti-Inflamatórios não Esteroides/química , Cloro/química , Cromatografia Líquida , Desinfetantes/química , Água Potável/química , Halogenação , Células Hep G2 , Humanos , Indóis/análise , Indóis/química , Indóis/toxicidade , Indometacina/análogos & derivados , Indometacina/análise , Indometacina/química , Indometacina/toxicidade , Espectrometria de Massas por Ionização por Electrospray/métodos , Poluentes Químicos da Água/química , Poluentes Químicos da Água/toxicidade , Purificação da Água/métodos
3.
Chemosphere ; 258: 127179, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32554002

RESUMO

Hydrophobic membranes for desalination and toxic organic pollutant removal have been fabricated using polyamide - PDMS (polydimethylsiloxane) chemistries in a one-step protocol. The curing of polyamide and PDMS are orthogonal and co-curing both networks imparts hydrophobicity to the thin film composite membranes. The membranes exhibit increased adsorption of pesticides from the feed water along with maintaining excellent salt rejection capability (97% NaCl rejection), thus giving the membranes a multifunctional character. Three toxic pesticides have been used in this study to demonstrate the viability of combining osmosis desalination technology with organic matter adsorption. The membranes also show excellent resistance to fouling by toxic pesticides (85% salt rejection vs 67% for commercial membranes in the presence of pesticides) and significantly improved chlorine tolerance (93.8% salt rejection vs 86.5% for commercial membranes after 20 h of exposure to sodium hypochlorite solution).


Assuntos
Cloro/química , Dimetilpolisiloxanos/química , Membranas Artificiais , Praguicidas/isolamento & purificação , Purificação da Água/instrumentação , Varredura Diferencial de Calorimetria , Interações Hidrofóbicas e Hidrofílicas , Nylons/química , Osmose , Espectrometria por Raios X , Termogravimetria , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos
4.
Food Chem ; 328: 127121, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32474241

RESUMO

Chlorine dioxide (ClO2) gas was utilized for detoxifying aflatoxin B1 (AFB1) in corn for the first time. Four degradation compounds were identified by LC-MS as C17H13O8, C17H15O10, C16H15O10, and C15H11O8. Structurally, the biological activity of ClO2-treated AFB1 was removed due to the disappearance of C8-C9 double bond in the furan ring and the modification of cyclopentanone and methoxy after ClO2 treatment. The cell viability assay on human embryo hepatocytes confirmed little toxicity of the degradation products. The degradation efficiency of AFB1 on corn peaked near 90.0% under the optimized conditions and reached 79.6% for low initial contamination of AFB1 at 5-20 µg/kg. Accordingly, ClO2 has the potential to be developed into an effective, efficient, and economic approach to detoxify AFB1 in grains.


Assuntos
Aflatoxina B1/química , Compostos Clorados/química , Cloro/química , Óxidos/química , Zea mays/química , Cromatografia Líquida de Alta Pressão , Espectrometria de Massas
5.
Chemosphere ; 251: 126469, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32443245

RESUMO

Cinnamic acid was chosen as an exemplar molecule to study the effect of potential contaminants on the kinetics and mechanism of the photocatalytic destruction of hydrocarbons in aqueous solutions. We identify the principal intermediates in the photocatalytic reaction of the acid and corresponding alcohol, and propose a mechanism that explains the presence of these species. The impact of two likely contaminants of aqueous systems, sulfate and chloride ions were also studied. Whereas sulfate ions inhibit the degradation reaction at all concentrations, chloride ions, up to a concentration of 0.5 M, accelerate the removal of cinnamic acid from solution by a factor of 1.6. However, although cinnamic acid is removed, the pathway to complete oxidation is blocked by the chloride, with the acid being converted (in the presence of oxygen) into new products including acetophenone, 2-chloroacetophenone, 1-(2-chlorophenyl)ethenone and 1,2-dibenzoylethane. We speculate that the formation of these products involves chlorine radicals formed from the reaction of chloride ions with the photoinduced holes at the catalyst surface. Interestingly, we have shown that the 1-(2-chlorophenyl)ethenone and 1,2-dibenzoylethane products form from 2-chloroacetophenone when irradiated with 365 nm light in the absence of the catalyst. The formation of potentially dangerous side products in this reaction suggest that the practical implementation of the photocatalytic purification of contaminated water needs to considered very carefully if chlorides are likely to be present.


Assuntos
Cinamatos/análise , Luz , Propanóis/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Catálise , Cloro/química , Cinamatos/efeitos da radiação , Oxirredução , Propanóis/efeitos da radiação , Sulfatos/química , Titânio/química , Poluentes Químicos da Água/efeitos da radiação
6.
Chemosphere ; 255: 126959, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32388263

RESUMO

The photolytic chlorination of n-alkanes in presence of sulfuryl chloride (SO2Cl2) was explored to produce new standard materials. Five mixtures of chlorinated tetradecanes were synthesized with chlorination degrees (mCl,EA) varying from 43.7% to 59.4% (m/m) based on elemental analysis. Chlorine-enhanced negative chemical ionization mass spectrometry (CE-NCI-MS) forcing the formation of chloride-adduct ions [M+Cl]- was applied to characterize these materials which all contained tetra-to deca-chlorinated paraffins. Deconvolution of respective mass spectra revealed the presence of chlorinated olefins (COs). CO levels were highest in materials, which were exposed longest. All synthesized materials also contained two classes of polar impurities, tentatively assigned as sulfite- and sulfate-diesters with molecular formulas of C14H28-xO3SClx (x = 1-4) and C14H28-xO4SClx (x = 3-6), respectively. MS data were in accordance with the proposed structures but further work is needed to deduce their constitutions. These compounds are thermolabile and were not detected with GC-MS methods. We could remove these sulfur-containing impurities from the CPs with normal-phase liquid chromatography. In conclusion, single-chain CP materials were synthesized via chlorination of n-alkanes with sulfuryl chloride, but these materials contained reactive side products which should be removed to gain non-reactive and stable CP materials suitable as standards and for fate and toxicity studies.


Assuntos
Hidrocarbonetos Clorados/química , Alcanos , Alcenos , Cloro/química , Cromatografia Gasosa-Espectrometria de Massas/métodos , Halogenação , Hidrocarbonetos Clorados/análise , Espectrometria de Massas/métodos , Parafina/análise
7.
Chemosphere ; 250: 126266, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32114343

RESUMO

The chloride ion (Cl-) is a matrix ion that plays crucial roles in radical-based oxidation processes used to treat brackish or saline water. Here, the effects of the formation of reactive chlorine species on the performance of and reaction mechanisms involved in persulfate/nano zero-valent iron process were evaluated by investigating the reaction kinetics and performing reactive species scavenging tests. The phenol oxidation rate increased markedly in the early reaction stage in the presence of 25-200 mM of Cl-. This was because excess sulfate radicals (SO4-) reacted with Cl- to produce short-lived reactive chlorine species such as Cl and Cl2- rather than being scavenged by Fe2+ or other SO4-. The reactive chlorine species caused OH to form through radical propagation reactions. The total numbers of reactive species involved in phenol oxidation were higher at brackish to weakly saline Cl- concentrations than at lower and higher Cl- concentrations. At high Cl- concentrations (>400 mM), the phenol oxidation rate decreased because most of the SO4- reacted with Cl- to give large amounts of weaker oxidants such as Cl2- and HOCl. Acceleration of Fe corrosion by Cl- negligibly affected the persulfate/nano zero-valent iron oxidation process.


Assuntos
Cloro/química , Nanopartículas Metálicas/química , Modelos Químicos , Cloretos/química , Ferro , Cinética , Oxirredução , Sulfatos/química
8.
Chemosphere ; 251: 126319, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32169717

RESUMO

Electro-adsorption is attracting increasing attention as an emerging technology for removing ionic species from water but suffer from low selectivity. In this work, a bismuth/reduced graphene oxide nanocomposite electrode was fabricated by a facile and green method. Based on this material, an electrode with improved selectivity by electrochemistry deionization system was successfully fabricated. The bismuth nanoparticles were uniformly covered with reduced graphene oxide plates and the ratio of Bi on the whole materials is 79.56%. Bismuth/reduced graphene oxide showed ions selectivity in the order of Cl- > F- ≫ [Formula: see text] . The average Cl- removal capacity can reach as high as 62.59 mg g-1. Moreover, bismuth/reduced graphene oxide electrodes have good regeneration performance. Typically, in the 10 adsorption-desorption multicycles, the salt absorption/desorption capacity of the hybrid capacitive deionization system is stable and reversible. This research opened a hopeful window to design and synthesize effective materials to selectively remove the ionic species to purify the water.


Assuntos
Cloro/química , Flúor/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Bismuto/química , Técnicas Eletroquímicas , Eletroquímica , Eletrodos , Grafite , Íons , Cloreto de Sódio
9.
Environ Sci Process Impacts ; 22(3): 792-801, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-32091522

RESUMO

Atrazine is a frequently detected groundwater contaminant. It can be microbially degraded by oxidative dealkylation or by hydrolytic dechlorination. Compound-specific isotope analysis is a powerful tool to assess its transformation. In previous work, carbon and nitrogen isotope effects were found to reflect these different transformation pathways. However, chlorine isotope fractionation could be a particularly sensitive indicator of natural transformation since chlorine isotope effects are fully represented in the molecular average while carbon and nitrogen isotope effects are diluted by non-reacting atoms. Therefore, this study explored chlorine isotope effects during atrazine hydrolysis with Arthrobacter aurescens TC1 and oxidative dealkylation with Rhodococcus sp. NI86/21. Dual element isotope slopes of chlorine vs. carbon isotope fractionation (Λ = 1.7 ± 0.9 vs. Λ = 0.6 ± 0.1) and chlorine vs. nitrogen isotope fractionation (Λ = -1.2 ± 0.7 vs. Λ = 0.4 ± 0.2) provided reliable indicators of different pathways. Observed chlorine isotope effects in oxidative dealkylation (εCl = -4.3 ± 1.8‰) were surprisingly large, whereas in hydrolysis (εCl = -1.4 ± 0.6‰) they were small, indicating that C-Cl bond cleavage was not the rate-determining step. This demonstrates the importance of constraining expected isotope effects of new elements before using the approach in the field. Overall, the triple element isotope information brought forward here enables a more reliable identification of atrazine sources and degradation pathways.


Assuntos
Atrazina , Biodegradação Ambiental , Cloro/química , Isótopos de Carbono , Fracionamento Químico , Isótopos de Nitrogênio
10.
Chemosphere ; 248: 126033, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32004882

RESUMO

Degradation of phenols with different substituent groups (including -OCH3, -CHO, -NHCOCH3, -NO2, and -Cl) at boron-doped diamond (BDD) anodes has been studied previously based on the removal efficiency and •OH detection. Innovatively, formations of CO2 gas and various inorganic ions were examined to probe the mineralization process combined with quantitative structure-activity relationship (QSAR) analysis. As results, all phenols were efficiently degraded within 8 h with high COD removal efficiency. Three primary intermediates (hydroquinone, 1,4-benzoquinone and catechol) were identified during electrochemical oxidation and degradation pathway was proposed. More importantly, CO2 transformation efficiency ranked as: no N or Cl contained phenols (p-CHO, p-OCH3 and Ph) > N-contained phenols (p-NHCOCH3 and p-NO2) > Cl-contained phenols (p-Cl and o,p-Cl). Carbon mass balance study suggested formation of inorganic carbon (H2CO3, CO32- and HCO3-) and CO2 after organic carbon elimination. Inorganic nitrogen species (NH4+, NO3- and NO2-) and chlorine species (Cl-, ClO3- and ClO4-) were also formed after N- and Cl-contained phenols mineralization, while no volatile nitrogen species were detected. The phenols with electron-withdrawing substituents were easier to be oxidized than those with electron-donating substituents. QSAR analysis indicated that the reaction rate constant (k1) for phenols degradation was highly related to Hammett constant (∑σo,m,p) and energy gap (ELUMO - EHOMO) of the compound (R2 = 0.908), which were key parameters on evaluating the effect of structural moieties on electronic character and the chemical stability upon radical attack for a specific compound. This study presents clear evidence on mineralization mechanisms of phenols degradation at BDD anodes.


Assuntos
Técnicas Eletroquímicas/instrumentação , Eletrodos , Fenóis/química , Relação Quantitativa Estrutura-Atividade , Poluentes Químicos da Água/química , Análise da Demanda Biológica de Oxigênio , Boro/química , Carbono/química , Dióxido de Carbono/química , Cloro/química , Diamante/química , Nitrogênio/química , Oxirredução
11.
Ecotoxicol Environ Saf ; 191: 110247, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-32004943

RESUMO

2,4-diaminobutyric acid (DAB), a newly identified algal toxins in water, pose a great threat to human health. DAB may react with chlorine or chloramine to produce CX3R-type disinfection by-products (DBPs) during water treatment processes. This study mainly investigated the formation and speciation of DBPs from chlor(am)ination of DAB. The results revealed that haloacetic acids (HAAs), trihalomethanes (THMs) and haloacetonitriles (HANs) were the main kinds of CX3R-type DBPs generated from DAB during chlor(am)ination, of which dichloroacetic acid yielded the highest. The formation and total toxicity of four CX3R-type DBPs from DAB during chloramination was significantly lower than that during chlorination at each Cl2:N molar ratio. However, more formation of Br-THMs and I-THMs were observed during chloramination in the presence of Br-/I-. Futhermore, the effects of chlor(am)ine dosage, solution pH, reaction time, and the concentration of Br- and I- on the formation and speciation of CX3R-type DBPs were also evaluated during chlor(am)ination. The plausible formation pathways of CX3R-type DBPs from DAB were proposed and verified by theoretical calculation. The quantum chemistry calculations indicate that 1N in DAB and 8N in 2,4-diaminochlorobutyric acid (C4H9O2N2Cl) were more likely to be attacked by electrophiles, supporting the proposed pathway schemes.


Assuntos
Aminobutiratos/química , Cloraminas/química , Cloro/química , Desinfetantes/química , Trialometanos/toxicidade , Poluentes Químicos da Água/toxicidade , Desinfecção/métodos , Halogenação , Trialometanos/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos
12.
Chemosphere ; 248: 125940, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32006828

RESUMO

This study examined the potential of six aliphatic and aromatic amides, commonly found in natural waters or used as chemical aids in water treatment, to act as organic precursors for nine haloacetamides (HAcAms), five haloacetonitriles (HANs), regulated trihalomethanes (THMs) and haloacetic acids (HAAs) upon chlorination and chloramination. The impact of key experimental conditions, representative of drinking water, including pH (7 & 8), retention time (4 & 24 h) and bromide levels (0 & 100 µg/L), on the generation of the target DBPs was investigated. The highest aggregate DBP yields upon chlor(am)ination were reported for the aromatic and hydrophobic hydroxybenzamide; 2.7% ± 0.1% M/M (chlorination) and 1.7% M/M (chloramination). Increased reactivity was observed in aliphatic and hydrophilic compounds, acrylamide (2.5 ± 0.2% M/M) and acetamide (1.3 ± 0.2% M/M), in chlorination and chloramination, respectively. The addition of bromide increased average DBP yields by 50-70%. Relative to chlorination, the application of chloramines reduced DBP formation by 66.5% (without Br-) and by 46.4% (with Br-). However, bromine incorporation in HAAs and HAcAms was enhanced following chloramination, of concern due to the higher toxicological potency of brominated compounds.


Assuntos
Desinfetantes/análise , Poluentes Químicos da Água/análise , Acetamidas , Amidas , Brometos/química , Bromo , Cloraminas/química , Cloro/química , Desinfetantes/química , Desinfecção , Halogenação , Trialometanos/química , Purificação da Água
13.
Chemosphere ; 248: 125957, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32006829

RESUMO

This study reports on the propranolol (PRO) degradation performance and product toxicity of an ultraviolet light-emitting diode (UV-LED)/chlorine process. The effects of experimental parameters including solution pH, chlorine dosage, and water matrix constituents on PRO removal were evaluated. Up to 94.5% of PRO could be eliminated within 15 min at a PRO-to-chlorine molar ratio of 1:4. The overall removal efficiency of PRO was non-pH dependent in the range of 5-9, while the initial rate was accelerated under alkaline conditions. The presence of Cl-/HCO3- had little influence on the PRO degradation, whereas either humic acid or NO3- had an obvious inhibitory effect. Radical scavenger experiments showed that both HO and Cl primarily contributed to the PRO degradation, and electron paramagnetic resonance data demonstrated the generation of 1O2. The transformation of PRO during this process led to five detected products, which exhibited a higher acute toxicity than the parent compound according to the bright luminescent bacillus T3 method. It is worth mentioning that under the same ultraviolet illumination intensity, the degradation of PRO under UV-LED/chlorine gave a better performance than UV254/chlorine, but the EEO of the former is obviously higher than the latter. So further research is required on improving the electric current to photon conversion efficiency for UV-LED. Additionally, the UV-LED/chlorine system was effective in the degradation of other drugs including sulfamethoxazole, oxytetracycline hydrochloride, and gatifloxacin, suggesting the possible application of the UV-LED/chlorine process for the removal of pharmaceuticals during wastewater treatment.


Assuntos
Propranolol/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Cloro/química , Substâncias Húmicas , Cinética , Oxirredução , Propranolol/toxicidade , Raios Ultravioleta , Águas Residuárias , Água , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
14.
Molecules ; 25(2)2020 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-31940837

RESUMO

We exploited a classic chemistry demonstration experiment based on the reaction of acetylene with chlorine to obtain highly crystalline graphite at ambient conditions. Acetylene and chlorine were generated in-situ by the addition of calcium carbide (CaC2) in a concentrated HCl solution, followed by the quick addition of domestic bleach (NaClO). The released gases reacted spontaneously, giving bursts of yellow flame, leaving highly crystalline graphite deposits in the aqueous phase. This was a rather benign alternative towards synthetic graphite, the latter usually being prepared at high temperatures. The synthetic graphite was further utilized to obtain graphene or conductive inks.


Assuntos
Acetileno/química , Cloro/química , Grafite/síntese química , Cristalização , Grafite/química , Microscopia de Força Atômica , Espectroscopia Fotoeletrônica , Análise Espectral Raman , Difração de Raios X
15.
Artigo em Inglês | MEDLINE | ID: mdl-31724470

RESUMO

Combined sewer overflow (CSO) water introduces pathogens to receiving waters. To control pathogenic releases, chlorine may be added to disinfect CSO water. The added chlorine may react with water constituents to form oxidative species known as chlorine-produced oxidants (CPO). CPO are the sum of free and combined oxidative species that form upon adding free chlorine-bearing compounds (e.g. gaseous chlorine or hypochlorite) to water. CPO discharge is often regulated by governing agencies. Current methods to model CPO behavior do not account for CPO decay and dilution simultaneously in receiving water. This study creates a novel model for CPO demand and dilution in receiving water from chlorinated effluent in order to determine site-specific practices for implementation of a CSO water disinfection regime. To do this, representative receiving water was collected and dosed with 1, 2, and 4 mg/L chlorine. The residual chlorine was measured at intervals up to 30 min after dosing. The immediate and subsequent chlorine demand was calculated, with the subsequent demand modeled by simultaneous application of dilution and decay using pseudo-first-order decay kinetics. A comparison of model calculations indicates that application of dilution before decay underestimates CPO demand, while application of decay before dilution overestimates CPO demand.


Assuntos
Cloro/química , Desinfetantes/química , Desinfecção/métodos , Oxidantes/química , Esgotos/química , Compostos Clorados/química , Modelos Químicos , Purificação da Água
16.
Sci Total Environ ; 703: 135513, 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-31761374

RESUMO

ß-N-Methylamino-l-alanine (BMAA), a new cyanobacterial toxin, is found in different aquatic ecosystems worldwide and is to threaten the human nervous system. Therefore, it is important for water plants to develop feasible methods to counter the effects of BMAA. In this study, the removal of BMAA by chlorine, as well as its intermediate products, at different pH values and the mechanism of pH on the removal BMAA were investigated. The results showed that the chlorination of BMAA is in accordance with the second-order kinetics model. The reaction rate of chlorinated BMAA increased with the increase in the concentration of chlorine. The pH of the solution significantly affected the reaction rate. The apparent kinetic constant (kapp) decreased from 6.00 × 103 M-1·min-1 to 35.5 M-1·min-1 when the pH increased from 4.5 to 9 in the chlorine concentration of 32.23 µM. It is probable that the species distribution and proportion of BMAA and chlorine at different pH values were the main causes of this phenomenon. Additionally, the chlorination reaction consisted of four elementary reactions and hydrogen ions were beneficial to the reaction. The temperature also affected the reaction rate and the activation energy of the reaction was 16.6 ± 1.99 kJ·M-1. A variety of degradation products were detected and the path of degradation was speculated. Chlorination, dechlorination, and decarboxylation were the main processes of oxidative degradation. Furthermore, the composition of the degradation products was the same at different pH values.


Assuntos
Diamino Aminoácidos/química , Cloro/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Diamino Aminoácidos/análise , Halogenação , Neurotoxinas/química , Poluentes Químicos da Água/análise
17.
Food Chem ; 310: 125832, 2020 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-31767490

RESUMO

Chemical doping with heteroatoms was employed to prepare N,Cl co-doped fluorescent carbon dots (N,Cl-FCDs) which may be designed for the detection of tartrazine. Using urea as the N source and FeCl3 ·â€¯6H2O as the Cl source, N,Cl-FCDs were synthesized by hydrothermal method with carbon dots prepared from aloe. Compared with pure carbon dots (CDs), N,Cl-FCDs resulted in dramatic improvement in the fluorescence properties and surface physical chemical properties. The fluorescence quantum yield of the N,Cl-FCDs was as high as 60.52%. As an effective fluorescence probe for tartrazine, a good linear relationship between N,Cl-FCDs and tartrazine was constructed at the concentration range from 0.1 to 30 µM with a detection limit of 48 nM based on the mechanism of fluorescence resonance energy transfer (FRET). The proposed fluorescent probe method was successfully applied to detect tartrazine in beverages, which is expected to have a potential application in the field of food analysis.


Assuntos
Bebidas/análise , Transferência Ressonante de Energia de Fluorescência/métodos , Corantes Fluorescentes/química , Pontos Quânticos/química , Tartrazina/análise , Carbono/química , Cloro/química , Corantes Fluorescentes/síntese química , Aditivos Alimentares/análise , Análise de Alimentos/métodos , Concentração de Íons de Hidrogênio , Limite de Detecção , Nitrogênio/química
18.
Clin Biochem ; 76: 38-41, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31809697

RESUMO

During the routine validation of a benzodiazepine method (performed on a Liquid Chromatography - Tandem Mass Spectrometer), it was noted that lorazepam, triazolam, and α-hydroxytriazolam showed a quadratic shift/bias in the calibration curve, particularly at high concentrations. The ultimate cause of this bias was determined to be due to the natural presence of chlorine (Cl) isotopes (35Cl and 37Cl) in these benzodiazepines. The presence of the heavy (37Cl) isoforms of Cl resulted in the analyte's mass being the same as the internal standard which, in turn, caused the internal standard to appear "falsely increased", thus skewing the calibration curve. One solution to this potential issue was to take advantage of this natural phenomenon and use the Cl heavy isoforms of the respectively labeled internal standards.


Assuntos
Benzodiazepinas/sangue , Cloro/química , Calibragem , Cromatografia Líquida , Humanos , Padrões de Referência , Espectrometria de Massas em Tandem
19.
Chemosphere ; 243: 125325, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31733542

RESUMO

The degradation of metoprolol (MTP), a ß-blocker commonly used for cardiovascular diseases, by UV/chlorine and UV/H2O2 processes was comparatively evaluated. MTP direct photolysis at 254 nm could be neglected, but remarkable MTP degradation was observed in both the UV/chlorine and UV/H2O2 systems. Compared with UV/H2O2, UV/chlorine has a more pronounced MTP degradation efficiency. In addition to primary radicals (OH and Cl), secondary radicals (ClO and Cl2-) played a pivotal role in degrading MTP by UV/chlorine process. The relative contributions of hydroxyl radicals (OH) and reactive chlorine species (RCS) in the UV/chlorine system varied at different solution pH values (i.e., the contribution of RCS increased from 57.7% to 75.1% as the pH increased from 6 to 8). The degradation rate rose as the oxidant dosage increased in the UV/chlorine and UV/H2O2 processes. The presence of Cl- slightly affected MTP degradation in both processes, while the existence of HCO3- and HA inhibited MTP degradation to different extents in both processes. In terms of the overall cost of electrical energy, UV/chlorine is more cost efficient than UV/H2O2. The degradation products during the two processes were identified and compared, and the degradation pathways were proposed accordingly. Compared with the direct chlorination of MTP, pre-oxidation with UV/chlorine and UV/H2O2 significantly enhanced the formation of commonly known DBPs. Therefore, when using UV/chlorine and UV/H2O2 in real waters to remove organic pollutants, the possible risk of enhanced DBP formation resulting from the degradation of certain pollutants during post-chlorination should be carefully considered.


Assuntos
Antagonistas de Receptores Adrenérgicos beta 1/química , Cloro/química , Peróxido de Hidrogênio/química , Metoprolol/química , Raios Ultravioleta , Cloretos , Halogenação , Radical Hidroxila , Modelos Químicos , Oxirredução , Fotólise , Purificação da Água/métodos
20.
Int J Radiat Biol ; 96(2): 236-244, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31633438

RESUMO

Purpose: Pharmacological medications can reduce the radiation damage in the organism when applied in the stage before or after exposure to radiation. Cholinergic drugs are a category of pharmaceutical agents acting on the neurotransmitter acetylcholine, the primary neurotransmitter in the parasympathetic nervous system. In this investigation, some gamma radiation interaction parameters namely mass attenuation coefficients (µρ), effective atomic number (Zeff) and electron densities (Nel) of 12 cholinergic system drugs have been calculated in the energy range 1 KeV-100 GeV. In addition, gamma-ray energy absorption (EABF) and exposure (EBF) of buildup factors have been computed using the five-parameter geometric progression (G-P) fitting formula for investigated drugs in the energy range 0.015-15 MeV, and for penetration depths up to 40 mean free path (mfp).Materials and methods: In order to perform these calculations, data obtained from WinXCom computer program were used. The computed µρ values were then used to calculate the effective atomic numbers and electron density of the investigated drugs. To compute the buildup factors, the G-P fitting parameters were determined by the method of interpolation from the equivalent atomic number, 'Zeq'Results and Conclusions: It has been concluded that effective atomic number and electron density of malathion is bigger than the other drugs and the variations in values of Zeff and Nel for all drugs depend on chemical compositions and photon energy where the K-absorption edge of elements may affect the energy dependence of Zeff and Nel. It should also be noted that the buildup of photons is less in malathion and carbachol and is more in tabun and parathion compared with other drugs. Photon interaction parameters evaluated in the present study may be beneficial in radiation dosimetry and therapy.


Assuntos
Acetilcolina/farmacologia , Acetilcolina/efeitos da radiação , Colinérgicos/farmacologia , Colinérgicos/efeitos da radiação , Raios gama , Algoritmos , Carbacol/farmacologia , Carbacol/efeitos da radiação , Cloro/química , Elétrons , Malation/farmacologia , Malation/efeitos da radiação , Modelos Estatísticos , Organofosfatos/farmacologia , Organofosfatos/efeitos da radiação , Paration/farmacologia , Paration/efeitos da radiação , Fósforo/química , Fótons , Probabilidade , Doses de Radiação , Radiometria , Espalhamento de Radiação , Software
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