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1.
J Environ Sci (China) ; 99: 59-71, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33183717

RESUMO

Organosilicas with chemically immobilized 3-aminopropyl and Methyl Red-containing surface groups were prepared by sol-gel condensation of tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane in the presence of dye as part of the mixed micelles or dye-containing silane as silica source. The hexagonally arranged mesoporous structure of synthesized materials was confirmed by low-temperature nitrogen adsorption-desorption, x-ray diffraction, and TEM studies. Chemical composition of MCM-41-type organosilicas was established by FT-IR spectroscopy and chemical analysis of surface layer. Sorption of Methyl Red by organosilicas was studied from diluted phosphate buffer solutions in dependence of medium pH, duration of contact, and equilibrium concentration of dye. It was found that effective removal of Methyl Red takes place at pH values within a range of 2.5-5. Kinetic curves of Methyl Red sorption on organosilicas were analyzed by the Lagergren, Ho-McKey, and Weber-Morris kinetic models. It was found that the pseudo-second-order model fits the kinetics of Methyl Red sorption on all synthesized materials and the intraparticle diffusion is not the only one mechanism controlling the rate of Methyl Red sorptive removal. The parameters of equilibrium sorption of Methyl Red on organosilicas of MCM-41 type were calculated using Langmuir, Freundlich, Redlich-Peterson, and Brunauer-Emmett-Teller models. Sorption of acid dyes with geometry similar or substantially different from Methyl Red on mesoporous silicas was studied from single and binary component mixtures in aqueous solutions with pH 4.8 and 5.5. It was found that selective sorption process is highly dependent on the structural characteristics and protolytic state of silica surface as well as acid dye.


Assuntos
Compostos Azo , Dióxido de Silício , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Soluções , Espectroscopia de Infravermelho com Transformada de Fourier
2.
Food Chem ; 337: 127759, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-32777568

RESUMO

High-resolution ultrasonic spectroscopy (HR-US) was applied for real-time monitoring of ß-casein hydrolysis by trypsin at various conditions for the first time. The technique is based on the precision measurement of hydration changes proportional to the number of peptide bond hydrolyzed. As HR-US exhibits ultrasonic transparency for most solution, the analysis did not require optical transparency like for 2,4,6-trinitrobenzenesulfonic acid (TNBS) assay. Appropriate enzymatic models were fitted with degree of hydrolysis (dh) profiles to provide kinetic and mechanistic description of proteolysis in terms of initial hydrolysis rate, r0, and rate constant of hydrolysis, kh, and enzyme inactivation, kd. Maximal r0 and dh were obtained at 45 °C and pH 8. The exponential dependence of kinetic parameters allowed determination of the activation (EA = 50.3 ± 7 kJ/mol) and deactivation (ED = 62.23 ± 3 kJ/mol) energies of hydrolysis. The ultrasonic assay provided rapid detection of trypsin activity even at sub-nanomolar concentration.


Assuntos
Caseínas/metabolismo , Ensaios Enzimáticos/métodos , Análise Espectral , Tripsina/metabolismo , Ondas Ultrassônicas , Ativação Enzimática , Hidrólise , Cinética , Proteólise , Soluções
3.
Chemosphere ; 261: 128144, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33113655

RESUMO

The improper disposal of waste containing toxic metals promotes serious environmental problems. Biosorption stands out as a powerful technique in removing toxic metals from aqueous solutions, making it an efficient and low-cost technique, since it makes use of abundant materials and of natural origins. This work aimed to study the application of the bark of Caryocar coriaceum Wittm, as a possible bioabsorbent for the removal of Lead (II) present in aqueous solutions, for this, residues of this material were collected in a public market, where they were washed and dried, then crushed, sieved (32mesh) and washed again, to then be used in the kinetic, isotherm and thermodynamic tests of lead (II) ions adsorption. After the experiments, it was found that the increase of the temperature disfavored the rate of lead (II) adsorption, ranging from 15.6 to 13.5 mg.L-1, for temperatures of 5 °C and 35 °C, respectively. The pseudo-second order kinetic model best characterizes the adsorption velocity obtaining a linear regression coefficient of 0.9997, while the pseudo-first order obtained a value of 0.7117. Adsorption occurred by chemisorption, with intra-film diffusion. The isothermal model that best represented the adsorption was Langmuir's (R2 0.99). It was concluded that the bark of Caryocar coriaceum Wittm is a good alternative to be used as a bioabsorbent for solutions containing dissolved lead (II).


Assuntos
Ericales/química , Chumbo/química , Modelos Teóricos , Casca de Planta/química , Poluentes Químicos da Água/análise , Adsorção , Difusão , Concentração de Íons de Hidrogênio , Íons , Cinética , Soluções , Termodinâmica
4.
Nat Commun ; 11(1): 5008, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-33024123

RESUMO

The potential of DNA as an information storage medium is rapidly growing due to advances in DNA synthesis and sequencing. However, the chemical stability of DNA challenges the complete erasure of information encoded in DNA sequences. Here, we encode information in a DNA information solution, a mixture of true message- and false message-encoded oligonucleotides, and enables rapid and permanent erasure of information. True messages are differentiated by their hybridization to a "truth marker" oligonucleotide, and only true messages can be read; binding of the truth marker can be effectively randomized even with a brief exposure to the elevated temperature. We show 8 separate bitmap images can be stably encoded and read after storage at 25 °C for 65 days with an average of over 99% correct information recall, which extrapolates to a half-life of over 15 years at 25 °C. Heating to 95 °C for 5 minutes, however, permanently erases the message.


Assuntos
Armazenamento e Recuperação da Informação/métodos , Hibridização de Ácido Nucleico , Sequência de Bases , Hibridização de Ácido Nucleico/métodos , Oligonucleotídeos/química , Pinturas , Soluções , Temperatura , Fatores de Tempo
5.
J Oleo Sci ; 69(10): 1241-1255, 2020 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-32908095

RESUMO

Measurements of aroxyl (ArO · )-radical-scavenging rate constants (ksAOH) of antioxidants (AOHs) (i.e., α-, ß-, γ-, δ-Tocopherol (TocH) and ubiquinol-10 (UQ10H2)) were performed in ethanol/chloroform/H2O (50/50/1, v/v) solution, using stopped-flow spectrophotometry. ksAOH values were measured not only for each AOH, but also for the mixtures of two AOHs (i.e., TocH and UQ10H2). ksTocH values for α-, ß-, γ-, δ-TocH increased 1.21, 1.28, 1.55, and 1.19 times, respectively, under the coexistence of constant concentrations of UQ10H2. Similar measurements were performed for eight vegetable oils 1 - 8, containing different concentrations of α-, ß-, γ-, δ-tocopherol (TocH) and -tocotrienol (Toc-3H). ksOil values of all eight vegetable oils 1 - 8 also increased 1.24 - 1.54 times under the coexistence of constant concentrations of UQ10H2. A new mechanism to explain the notable increase of ksAOH values under the coexistence of two kinds of phenolic AOHs was proposed. UV-vis absorption of α-, ß-, γ-Toc · radicals, produced by reaction of α-, ß-, γ-TocHs (or vegetable oils 1 - 8) with ArO · , disappeared under the coexistence of TocHs (or oils) and UQ10H2, suggesting that the prooxidant reaction resulting from the presence of Toc · radicals is suppressed in the presence of UQ10H2.


Assuntos
Antioxidantes/química , Depuradores de Radicais Livres/química , Óleos Vegetais , Ubiquinona/análogos & derivados , Vitamina E/química , Clorofórmio , Etanol , Oxirredução , Óleos Vegetais/química , Soluções , Espectrofotometria/métodos , Ubiquinona/química , Água
6.
PLoS One ; 15(8): e0237271, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32866161

RESUMO

Molecular separation of pharmaceutical contaminants from water has been recently of great interest to alleviate their detrimental impacts on environment and human well-being. As the novelty, this investigation aims to develop a mechanistic modeling approach and consequently its related CFD-based simulations to evaluate the molecular separation efficiency of ibuprofen (IP) and its metabolite 4-isobutylacetophenone (4-IBAP) from water inside a porous membrane contactor (PMC). For this purpose, octanol has been applied as an organic phase to extract IP and 4-IBAP from the aqueous solution due to high solubility of solutes in octanol. Finite element (FE) technique is used as a promising tool to simultaneously solve continuity and Navier-Stokes equations and their associated boundary conditions in tube, shell and porous membrane compartments of the PMC. The results demonstrated that the application of PMC and liquid-liquid extraction process can be significantly effective due to separating 51 and 54% of inlet IP and 4-IBAP molecules from aqueous solution, respectively. Moreover, the impact of various operational / functional parameters such as packing density, the number of fibrous membrane, the module length, the membrane porosity / tortuosity, and ultimately the aqueous solution flow rate on the molecular separation efficiency of IP and 4-IBAP is studied in more details.


Assuntos
Acetofenonas/isolamento & purificação , Anti-Inflamatórios não Esteroides/isolamento & purificação , Ibuprofeno/isolamento & purificação , Membranas Artificiais , Polímeros/química , Extração Líquido-Líquido/métodos , Octanóis/química , Porosidade , Solubilidade , Soluções
7.
Chemosphere ; 254: 126905, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957298

RESUMO

With the development of modern technologies, the exploitation and application of rare earth metals (REMs) have increased parallelly. Consequently, more REMs are entering into the environment and therefore there is a pressing need to assess their potential environmental hazards. Here, a standard toxicity test with wheat (Triticum aestivum) was conducted to investigate the single and mixture toxicity of La and Ce in solutions with different levels of calcium and nitrilotriacetic acid (NTA) and results were deciphered by different modeling approaches. Both La and Ce caused adverse effect to wheat, but the presence of Ca and NTA alleviated their toxicity. The obtained EC50 for [La] or [Ce] changed by more than 28-fold and by 4-fold, respectively, with the increase of Ca or NTA. The biotic ligand model (BLM) explained approximately 93% variation of single La or Ce toxicity. The binding constants obtained were 4.14, 6.67, and 6.59 for logKCaBL, logKLaBL, and logKCeBL respectively. The electrostatic toxicity model (ETM) was proved as effective as the BLM, with R2 = 0.93 for La and R2 = 0.92 for Ce. For La-Ce mixtures, parameters from single toxicity approaches were applied successfully to predict the mixture toxicity with concentration addition (CA) model based on the BLM or ETM theory (R2 = 0.92 and RMSE = 8.56; R2 = 0.90 and RMSE = 9.6, respectively). Thus, the results obtained in this study prove that both ETM and BLM theories are appropriate to predict single and mixture REMs toxicity, providing coherent and promising tools for the risk assessment of REM pollution.


Assuntos
Cálcio/química , Cério/toxicidade , Lantânio/toxicidade , Ácido Nitrilotriacético/química , Testes de Toxicidade/métodos , Triticum/efeitos dos fármacos , Ligantes , Modelos Teóricos , Soluções , Eletricidade Estática , Triticum/crescimento & desenvolvimento
8.
PLoS One ; 15(9): e0238573, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32877463

RESUMO

Sugars are commonly supplemented into vitrification solution to dehydrate cells in order to reduce the formation of fatal intracellular ice crystals. Natural honey is a mixture of 25 sugars (mainly fructose and glucose) that have different biological and pharmacological benefits. The present study was designed to determine if honey can be used as a nonpermeating cryoprotectant in vitrification of bovine oocytes. In the first experiment, denuded-MII oocytes were exposed to 0.25, 0.5, 1.0, 1.5 or 2.0 M of honey or sucrose. Natural honey and sucrose caused similar ooplasm dehydration. A significant relationship existed between time and ooplasm volume change (P < 0.05), during dehydration and rehydration phases, in both honey and sucrose solutions. In the second experiment, the immature cumulus-oocyte complexes (COCs) were vitrified in an EG/DMSO-based vitrification solution containing honey (0.5, 1 or 1.5 M) or sucrose (0.5 M) as a gold standard. The vitrified-warmed COCs were matured in vitro and evaluated for nuclear maturation. The maturation (MII) rate was greater in nonvitrified control (81%) than vitrified groups (54%, P < 0.05). In the third experiment, COCs were either remained nonvitrified (control) or vitrified in 1.0 M honey or 0.5 M sucrose, followed by IVM, IVF and IVC (for 9 days). Cleavage rate was greater in control (74%) than in vitrified groups (47%, P < 0.05), without significant difference between sugars. Blastocyst rate was 34, 13 and 3% in control, honey and sucrose groups respectively (P < 0.05). In conclusion, natural honey acted as a nonpermeating cryoprotectant in vitrification solution and improved the embryonic development in vitrified bovine COCs.


Assuntos
Crioprotetores/farmacologia , Mel , Oócitos/citologia , Vitrificação , Animais , Blastocisto/citologia , Bovinos , Desidratação , Técnicas de Maturação in Vitro de Oócitos , Oócitos/efeitos dos fármacos , Concentração Osmolar , Análise de Regressão , Soluções , Sacarose/farmacologia
9.
J Chromatogr A ; 1628: 461470, 2020 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-32822993

RESUMO

Hypercrosslinked polymers (HCPs) have demonstrated effective adsorption capabilities because of their rich porosity and high specific surface area. However, the HCPs prepared with phenylboronic acid based compounds as monomers via Friedel-Crafts alkylation reaction have not been reported yet. Herein, four new HCPs with phenylboronic acid (PBA), 1,4-benzenediboronic acid, 4-hydroxyphenylboronic acid and 4-carboxyphenylboronic acid as the respective monomers were prepared for the first time. Their Brunner-Emmet-Teller surface areas were 909.1 m2 g-1, 71.9 m2 g-1, 39.8 m2 g-1 and 29.3 m2 g-1, respectively. The prepared HCP with PBA as the monomer (named as PBA-HCP) displayed the best adsorption capability for chlorophenols. Then, it was investigated as a SPE adsorbent for the extraction of some chlorophenols from water and honey-pomelo beverage samples prior to high performance liquid-phase chromatography with diode array detection. The established method had low limits of detection for the analytes in the range from 0.06 to 0.2 ng mL-1 for water samples and from 0.3 to 1.0 ng mL-1 for honey-pomelo beverage samples. The linear response for the analytes was in the range of 0.18-100.0 ng mL-1 for water samples and 0.9-100.0 ng mL-1 for honey-pomelo beverage samples. The method also had a good repeatability with the relative standard deviations less than 7.1% and a fairly good accuracy with the method recoveries falling between 80.0% and 120.0%. The adsorption capacities of the PBA-HCP for 2-chlorophenol, 3-chlorophenol, 2,3-dichlorophenol and 2,4-dichlorophenol were 21.7 mg g-1, 31.2 mg g-1, 77.1 mg g-1 and 82.1 mg g-1, respectively. The PBA-HCP also exhibited excellent extraction capabilities for some other compounds, especially for those that have more hydrogen bonding sites.


Assuntos
Ácidos Borônicos/química , Clorofenóis/isolamento & purificação , Reagentes para Ligações Cruzadas/química , Polímeros/química , Adsorção , Cromatografia Líquida de Alta Pressão , Concentração de Íons de Hidrogênio , Limite de Detecção , Nitrogênio/química , Porosidade , Reprodutibilidade dos Testes , Extração em Fase Sólida , Soluções , Solventes/química , Temperatura , Poluentes Químicos da Água/análise
10.
AAPS PharmSciTech ; 21(6): 221, 2020 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-32748291

RESUMO

Sildenafil citrate causes vasodilatation, relaxation of the smooth muscle, and reduction of pulmonary arterial pressure. The latter property makes sildenafil citrate efficient for the treatment of cardiovascular diseases, including pulmonary arterial hypertension. Pediatric patients with pulmonary arterial hypertension are more susceptible to errors in drug administration than adults because of a lack of suitable drug dosages. Thus, the purpose of this study was to develop stable (chemically and microbiologically) sildenafil citrate drop liquid formulation, suitable for pediatric patients (including diabetics), ensuring safety during preparation and storing and improving palatability by using milk as a carrier for administration. The significant factors that affect the sildenafil solubility were evaluated by applying a Plackett-Burman design using two levels with six variables. The experiment showed that the type of buffer and glycerin content influenced the sildenafil solubility. The developed formulations proved to be stable for 6 months at all three assayed conditions (40± 2°C, 75 ± 5% RH; 25± 2°C, 60 ± 5% RH; and 4 ± 2°C). The microbiological tests fit with the requirement of the pharmacopeia at day 0 and 90 and even more at day 180. Finally, the palatability assay showed that 0.82 mL of the formulation containing buffer phosphate, 20% glycerin, and 4 mg mL-1 of sildenafil citrate diluted in 4.8 mL milk (which fits the medium pediatric dose) presented similar palatability to milk alone, and no precipitate or turbidity was observed. Graphical abstract.


Assuntos
Hipertensão Pulmonar/tratamento farmacológico , Citrato de Sildenafila/química , Adulto , Criança , Composição de Medicamentos , Estabilidade de Medicamentos , Humanos , Pessoa de Meia-Idade , Citrato de Sildenafila/uso terapêutico , Solubilidade , Soluções
11.
Artigo em Inglês | MEDLINE | ID: mdl-32824583

RESUMO

The paper presents the results of laboratory tests on possibilities to utilize active carbons produced in Poland (AG-5 and DTO) and clinoptilolite for removing naphthalene from a water solution in the adsorption process. The concentration of naphthalene in the model solution was 20 mg/dm3. The effects of pH, dose and adsorption time were determined under static conditions. Adsorption kinetics were consistent with the pseudo-second-order model (PSO). Among the applied models, the best fit was obtained using the Langmuir isotherms. The maximum adsorption capacity for the activated carbons (AG-5 and DTO) equaled 24.57 and 30.28 mg/g, respectively. For clinoptilolite, all the analyzed models of adsorption poorly described the adsorption process. The flow conditions were realized by filtration method. On the basis of the obtained results, the breakthrough curves, so-called isoplanes, were prepared and served in turn to determine the adsorption capacities in flow conditions. The total adsorption capacities determined under dynamic conditions of the AG-5 and DTO activated carbons were 85.63 and 94.54 mg/g, respectively, and only 2.72 mg/g for clinoptilolite. The exit curves (isoplanes) were also utilized to determine the mass penetration zone (the adsorption front height), as well as to calculate the rate of mass-exchange zone advance.


Assuntos
Naftalenos , Poluentes Químicos da Água , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Polônia , Soluções , Água , Purificação da Água
12.
Plast Reconstr Surg ; 146(2): 301-308, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32740580

RESUMO

BACKGROUND: Infections are challenging complications of implant-based breast reconstruction and augmentation. They pose a clinical challenge, with significant economic implications. One proposed solution is implant irrigation at the time of placement. There is no consensus on the optimal irrigant solution. METHODS: The authors tested the relative efficacy of 10% povidone-iodine, Clorpactin, Prontosan, triple-antibiotic solution, or normal saline (negative control) against two strains each of methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis. Sterile, smooth silicone implant disks were immersed in irrigant solution, then incubated in suspensions of methicillin-resistant S. aureus or S. epidermidis overnight. The disks were rinsed and sonicated to displace adherent bacteria from the implant surface, and the displaced bacteria were quantified. Normalized values were calculated to characterize the relative efficacy of each irrigant. RESULTS: Povidone-iodine resulted in reductions of the bacterial load by a factor of 10 to 10 for all strains. Prontosan-treated smooth breast implant disks had a 10-fold reduction in bacterial counts for all but one methicillin-resistant S. aureus strain. In comparison to Prontosan, triple-antibiotic solution demonstrated a trend of greater reduction in methicillin-resistant S. aureus bacterial load and weaker activity against S. epidermidis strains. Clorpactin reduced the recovered colony-forming units for only a single strain of S. epidermidis. Povidone-iodine demonstrated the greatest efficacy against all four strains. However, Clorpactin, triple-antibiotic solution, and Prontosan demonstrated similar efficacies. CONCLUSIONS: Povidone-iodine was the most efficacious of the irrigants at reducing methicillin-resistant S. aureus and S. epidermidis contamination. Given the recent lifting of the U.S. Food and Drug Administration moratorium, larger clinical studies of povidone-iodine as a breast implant irrigant solution are warranted. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.


Assuntos
Anti-Infecciosos Locais/administração & dosagem , Biofilmes/efeitos dos fármacos , Implante Mamário/efeitos adversos , Implantes de Mama/microbiologia , Infecções Relacionadas à Prótese/prevenção & controle , Bacitracina/administração & dosagem , Benzenossulfonatos/administração & dosagem , Implante Mamário/instrumentação , Cefazolina/administração & dosagem , Combinação de Medicamentos , Gentamicinas/administração & dosagem , Humanos , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Staphylococcus aureus Resistente à Meticilina/isolamento & purificação , Povidona-Iodo/administração & dosagem , Infecções Relacionadas à Prótese/microbiologia , Soluções , Staphylococcus epidermidis/efeitos dos fármacos , Staphylococcus epidermidis/isolamento & purificação , Irrigação Terapêutica/métodos
13.
J Environ Manage ; 271: 110970, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32778274

RESUMO

The concentrative isolation of metal traces from aqueous solutions is of vital importance for environmental and industrial processes. Developing reliable systems of nanoscale that can be fine-tuned to effectively isolate these metals remains an intriguing aim which can potentially beget economic benefits and mitigate major environmental concerns. Here we demonstrate a conceptual metal extraction system where magnetic multi-wall carbon nanotubes (M-MWCNTs) are surface-equipped with a molecular network of polyethylenimine (PEI) to serve as a reusable nano-ionic exchanger, referred to as "M-MWCNTs-PEI". The designed nano-ionic exchanger forms readily stable suspensions with the metal-bearing aqueous solutions eliminating the need for vigorous agitation. Besides, it can be magnetically manipulated and separated in/from the solution. To exemplify its potential for the isolation of metal traces, the M-MWCNTs-PEI was tested with the uranium trace ions in aqueous media. The M-MWCNTs-PEI featured distinct sorption capacity of ~488 mg/g at pH 6, with moderate, but stable, binding affinity toward uranium ions. As such, excellent isolation performance is demonstrated while bound uranium ions are effectively concentrated and recovered from the interfacial PEI molecular network. This was efficiently achieved by exposing the loaded M-MWCNTs-PEI to solutions of small volumes and specific chemistry. Such combined qualities of large capacity and reusability have not been observed with the previously reported ion exchange systems. Altogether, our observations here demonstrate how functional systems of nanoscale can be adapted for industrial applications while this concept can be extended to address other important resources such as rare-earth and lanthanide elements.


Assuntos
Nanotubos de Carbono , Urânio , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Fenômenos Magnéticos , Soluções , Suspensões
14.
J Chromatogr A ; 1629: 461473, 2020 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-32841769

RESUMO

Liquid chromatography tandem mass spectrometry has been a widely used technique for quantifying oligonucleotides in biological samples. However, lack of simple and efficient sample cleanup approach remains a challenge. Our study aimed to evaluate the major factors during the sample pretreatment process for developing optimal sample preparation workflow for oligonucleotides. In this study, we have employed a model formed with rat plasma containing a 16 mer oligonucleotide standard in order to comprehensively optimize the sample preparation procedures. These included liquid-liquid extraction (LLE), solid-phase extraction (SPE), protein precipitation (PPT) and LLE combined with SPE. LLE with phenol: dichloromethane (2:1, v:v) was found to be the most efficient sample cleanup procedure with low cost and less toxicity. Followed by the extraction, ethanol precipitation (-80 °C, 5 min) was determined to be the optimal drying conditions. Also, mass spectrometric parameters were tuned to optimal conditions. It was found that the central composite design suite was proved to be highly practical for optimizing MS parameters. Finally, the thoroughly optimized sample preparation workflow was fully validated. The developed assay provided a quantitative range of 0.25-1000 nM, with accuracy and precision were < 7.45% and < 12.20%, respectively. Matrix effect and carryover were also evaluated and no significant effect was observed.


Assuntos
Métodos Analíticos de Preparação de Amostras , Oligonucleotídeos/análise , Espectrometria de Massas em Tandem/métodos , Adsorção , Animais , Clorofórmio/química , Cromatografia Líquida de Alta Pressão/métodos , Cromatografia Líquida/métodos , Dessecação , Glicogênio/química , Concentração de Íons de Hidrogênio , Extração Líquido-Líquido , Cloreto de Metileno/química , Fenol/química , Fosfolipídeos/isolamento & purificação , Ratos , Reprodutibilidade dos Testes , Extração em Fase Sólida , Soluções , Fluxo de Trabalho
15.
Leg Med (Tokyo) ; 47: 101765, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32769017

RESUMO

Quantitative analysis of thiosulfate is useful for diagnosing hydrogen sulfide poisoning. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) enables more rapid and sensitive measurements than previous methodologies. As simple measurements of blood thiosulfate concentration are affected by the blood matrix, blood is used as the solvent to prepare the standard solution for calibration curve generation. Thus, a large amount of blood devoid of thiosulfate is required. We developed a preparation method by incorporating an ultrafiltration step to overcome this limitation and generate a calibration curve using a standard solution prepared with pure water. We used this improved method to investigate the stability of thiosulfate in refrigerated samples. To compare the effects of refrigeration, blood samples were prepared using the following two methods: one sample was treated with a 50-kDa exclusion ultrafiltration membrane and the other was not treated. The samples were stored at 4 °C, and then measured at 0, 3, 6, 24, 48, and 96 h. The incorporation of the ultrafiltration step in the measurement procedure enabled the quantification of thiosulfate, by plotting a calibration curve using a standard of pure water; it did not require a blood standard. Additionally, the reduction in whole blood thiosulfate concentration was within 10% during 2 days of refrigeration. Thus, the need for a large amount of blood to prepare the standard solution was resolved by the ultrafiltration step in test sample preparation. This method is useful to measure thiosulfate concentration and is not hindered by sample refrigeration for a few days.


Assuntos
Toxicologia Forense/métodos , Sulfeto de Hidrogênio/envenenamento , Manejo de Espécimes/métodos , Tiossulfatos/sangue , Ultrafiltração/métodos , Calibragem , Humanos , Refrigeração , Soluções , Água
16.
J Chromatogr A ; 1626: 461349, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797829

RESUMO

In the present work, a very sensitive and fully automated direct immersion PAL SPME Arrow procedure, coupled with GC-MS, has been developed and validated for determination of nine phosphorus flame retardants in different types of water samples (river, drinking and rainwater). PDMS/DVB was selected among three commercially available SPME Arrows (PDMS/DVB, DVB/PDMS/CWR and PDMS/CWR), since it resulted in the best sensitivity. The important experimental parameters were optimized via a central composite design response surface methodology and as result, extraction time of 65 min, extraction temperature of 80 °C and added salt concentration of 19% (w/v), were selected as the optimum values. The optimized method showed linear response over the calibration range (2 - 500 ng L-1), with R2-values higher than 0.9937. The precision (RSD%) measured by replicate analyses (n = 7) was estimated at 2 and 100 ng L-1 and was less than 29% and 21%, respectively. The LOQ of PAL SPME Arrow, calculated as S/N = 10, was between 0.2 and 1.2 ng L-1 (for triphenyl phosphate and tris-(1­chloro­2-propyl) phosphate, respectively) with extraction efficiencies between 5.9 and 31% (for tris-(1,3-dichloro-2-propyl) phosphate and tri-n­butyl phosphate, respectively). To assess the performance of the developed technique for real samples, two river water samples, tap water from two regions and a rainwater sample were analyzed. Most of the target analytes were observed in the river samples with concentrations of 1.0 - 250 ng L-1 and the obtained recoveries at 50 ng L-1 ranged between 60 and 107%. Considering the figures of merit of the optimized method, PAL SPME Arrow-GC-MS showed to be the most sensitive analytical approach for determination of phosphorus flame retardants in water, with satisfying precision and accuracy, compared with conventional SPME-NPD, LLE-GC-MS and SPE-LC-MS/MS.


Assuntos
Retardadores de Chama/análise , Fósforo/análise , Microextração em Fase Sólida/métodos , Poluentes Químicos da Água/análise , Automação , Dimetilpolisiloxanos/química , Cromatografia Gasosa-Espectrometria de Massas , Polivinil/química , Soluções
17.
Chemosphere ; 260: 127683, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32758774

RESUMO

This study represents the first ever work on a novel oxone treated hydrochar as an adsorbent for the efficient removal of different contaminants from aqueous solutions. Pine wood hydrochar (HC) was prepared by hydrothermal treatment at 300 °C and oxidized with oxone to produce oxidized pine wood hydrochar (OHC). Different analytical tools such as elemental analysis, FTIR, TGA, FE-SEM, and BET were used for the characterization of the OHC. Conductometric titration of OHC showed a substantial increase from 22 µmol/g to 600 µmol/g in the hydrochar carboxylic content. The OHC sorption performance was assessed by using Pb(II) ions and methylene blue (MB) dye as two models of contaminants. Sorption benchmarks were performed by varying the contaminant initial concentration, time, and temperatures. Sorption kinetic data was fitted well to the pseudo-second order kinetic model with high correlation coefficients (R2 > 0.99) and isothermal data was fitted to the Langmuir model. The highest adsorption capacities for MB and Pb(II) were 86.7 mg/g and 46.7 mg/g, respectively. This study proves that oxone treatment could be a potential sustainable oxidation method to tune the hydrochar surface to increase selectivity towards heavy metal ions and dye sorption.


Assuntos
Chumbo/química , Azul de Metileno/química , Poluentes Químicos da Água/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Metais Pesados , Azul de Metileno/análise , Soluções , Ácidos Sulfúricos , Temperatura , Água , Poluentes Químicos da Água/análise
18.
J Oleo Sci ; 69(9): 1021-1030, 2020 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-32788513

RESUMO

A novel jellyfish-shaped triazine hexamer quaternary ammonium chloride surfactant (TH12QC) was synthesized, which consisted of one triazine spacer group and six long flexible hydrophobic chains. The molecular structure and aggregation behavior of TH12QC was investigated by nuclear magnetic resonance (NMR), surface tension, electrical conductivity, dynamic light scattering (DLS), transmission electron microscope (TEM), etc. The results show that the jellyfish-shaped TH12QC has better surface activity and lower surface tension than traditional ionic and Gemini surfactants in aqueous solution. There are two inflection points in the curve of conductivity versus concentration of the TH12QC aqueous solution, which correspond to the critical aggregation concentration (CAC) and the critical micelle concentration (CMC) respectively. The existence of CAC indicates that there is a pre-aggregation process before TH12QC forms micelles. The results of DLS and TEM show that network pre-aggregation, spherical aggregation and dense spherical aggregation were observed in different concentration of TH12QC aqueous solution, and the electrostatic equilibrium of the system subtly depends on the concentration of the solution. In addition, intramolecular and intermolecular hydrogen bonding is also an important factor. This study provides a method for studying the aggregation behavior and morphology of oligomeric surfactants with rigid spacer groups.


Assuntos
Cloreto de Amônio/química , Cloreto de Amônio/síntese química , Compostos de Amônio Quaternário/química , Compostos de Amônio Quaternário/síntese química , Tensoativos/química , Tensoativos/síntese química , Triazinas/química , Triazinas/síntese química , Fenômenos Químicos , Difusão Dinâmica da Luz , Condutividade Elétrica , Ligação de Hidrogênio , Micelas , Estrutura Molecular , Soluções , Tensão Superficial , Água/química
19.
J Chromatogr A ; 1627: 461390, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823096

RESUMO

A dispersive solid phase extraction method was combined with deep eutectic solvent-based solidification of floating organic drop-dispersive liquid-liquid microextraction and used for the extraction/preconcentration of some organophosphorus pesticides residues from edible oil samples. The extracted analytes were quantified with gas chromatography-nitrogen phosphorous detector. In this procedure, the sample lipids are saponified with a sodium hydroxide solution and then the analytes are adsorbed onto a primary secondary amine sorbent. After that the analytes are desorbed with acetone as an elution/dispersive solvent and mixed with choline chloride: 3,3-dimethyl butyric acid deep eutectic solvent and the mixture is rapidly dispersed into deionized water. Then, the obtained cloudy solution is centrifuged and placed into an ice bath. The extraction solvent is solidified on the top of the solution. Finally, it is removed and dissolved in acetonitrile, and 1 µL of the solution is injected into the separation system. Validation of the method showed that limits of detection and quantification were in the ranges of 0.06-0.24 and 0.20-0.56 ng mL-1, respectively. Enrichment factors and extraction recoveries of the analytes ranged from 170-192 and 68-77%, respectively. The method had an acceptable precision with relative standard deviations less than ≤9.2% for intra- (n=6) and inter-day (n=6) precisions at four concentrations (3, 10, 50, and 250 ng mL-1, each analyte). Finally the method was used for determination of the analytes in five edible oil samples.


Assuntos
Microextração em Fase Líquida/métodos , Compostos Organofosforados/análise , Praguicidas/análise , Óleos Vegetais/química , Extração em Fase Sólida/métodos , Solventes/química , Acetonitrilos/química , Reprodutibilidade dos Testes , Hidróxido de Sódio/química , Soluções , Sonicação , Fatores de Tempo
20.
Food Chem ; 333: 127460, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32673953

RESUMO

Arbutus unedo L. (strawberry tree) has showed considerable content in phenolic compounds, especially flavan-3-ols (catechin, gallocatechin, among others). The interest of flavan-3-ols has increased due their bioactive actions, namely antioxidant and antimicrobial activities, and by association of their consumption to diverse health benefits including the prevention of obesity, cardiovascular diseases or cancer. These compounds, mainly catechin, have been showed potential for use as natural preservative in foodstuffs; however, their degradation is increased by pH and temperature of processing and storage, which can limit their use by food industry. To model the degradation kinetics of these compounds under different conditions of storage, three kinds of machine learning models were developed: i) random forest, ii) support vector machine and iii) artificial neural network. The selected models can be used to track the kinetics of the different compounds and properties under study without the prior knowledge requirement of the reaction system.


Assuntos
Ericaceae/química , Conservantes de Alimentos/química , Aprendizado de Máquina , Extratos Vegetais/química , Antioxidantes/química , Catequina/análise , Catequina/química , Flavonoides/análise , Flavonoides/química , Armazenamento de Alimentos , Frutas/química , Concentração de Íons de Hidrogênio , Cinética , Redes Neurais de Computação , Pós/análise , Pós/química , Soluções/química , Máquina de Vetores de Suporte , Temperatura
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