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1.
Acta Odontol Latinoam ; 33(2): 135-142, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32920616

RESUMO

This study evaluated the influence of the mode and time of solvent evaporation on the tensile strength (TS), flexural strength (FS) and elastic modulus (EM) of two adhesive systems: Scotchbond Multipurpose (SBMP) and Clearfil SE (CSEB). For this purpose, rectangular samples (2x1x7 mm) were prepared with 10 µL of primer and the solvents were evaporated with air spray at (23±1) ºC, (40±1) ºC and negative control (without spray). For each temperature, the times of 5, 20, 30, and 60 seconds were investigated. The statistical results showed that evaporation at 40±1ºC resulted in better EM for the two adhesives tested and all the evaporation times evaluated. However, there were no significant differences between the times and modes of evaporation for TS. The results of this study indicate that evaporation at a temperature of (40±1) °C could improve the elastic modulus of both adhesives tested, regardless of the evaporating time.


Assuntos
Adesivos/química , Cimentos Dentários/química , Adesivos Dentinários/química , Solventes/farmacologia , Resistência à Tração , Dessecação , Humanos , Teste de Materiais , Volatilização
2.
J Environ Sci (China) ; 97: 67-74, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32933741

RESUMO

Molecular level characterization of dissolved organic sulfur (DOS) by electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR MS) is necessary for further understanding of the role of DOS in the environment. Here, ESI spray solvent, a key parameter for ion production during ESI process, was investigated for its effect on the molecular characterization of DOS by ESI-FTICR MS. 100% MeOH as spray solvent was found for the first time to remarkably enhance the ionization efficiency of the majority of CHOS-molecules in NOM, which facilitated a total of 1473 CHOS-molecular formulas with one sulfur atom to be detected. The number of CHOS-molecular formulas obtained using 100%MeOH as spray solvent increased notably over 740 in comparison with those using 50% MeOH aqueous solution (731) or 50% ACN aqueous solution (653). Moreover, due to the enhancement of ionization efficiency of DOS during ESI processes, the tandem mass spectra of the NOM CHOS-molecules could be easily obtained using 100% MeOH as spray solvent, which were hardly obtained using 50% MeOH aqueous solution as spray solvent. The results of the tandem mass spectra suggested the first discovery of organosulfates or sulfonic acids in Suwannee River NOM sample. A simple method based on 100% MeOH as ESI spray solvent for advanced molecular characterization of DOS by ESI-FTICR MS was proposed and applied, and the results revealed more molecular information of DOS in sea DOM samples.


Assuntos
Ciclotrons , Espectrometria de Massas por Ionização por Electrospray , Análise de Fourier , Solventes , Enxofre
3.
BMC Cardiovasc Disord ; 20(1): 415, 2020 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-32928149

RESUMO

BACKGROUND: Methanol is widely used in industry; however, methanol poisoning is not common. In this regard, a number of outbreaks have been recently reported due to inappropriate processing of alcoholic beverages. Shiraz, a city located in the southern part of Iran, faced one of such outbreaks in 2020 during COVID-19 pandemic. There is no sufficient literature on the electrocardiographic findings in methanol toxicity. This study aimed to address this gap in the literature. METHOD: A total of 356 cases with methanol toxicity referred to Shiraz University of Medical Science Tertiary Hospitals (Faghihi and Namazi) in March and April, 2020. The clinical findings of blindness and impaired level of consciousness, lab data such as arterial blood gas, electrolytes, and creatinine, and the most common findings from ECGs were collected. RESULTS: The most common ECG findings were J point elevation (68.8%), presence of U wave (59.2%), QTc prolongation (53.2% in males and 28.6% in females), and fragmented QRS (33.7%). An outstanding finding in this study was the presence of myocardial infarction in 5.3% of the cases. This finding, to the best of our knowledge, has only been reported in a few case reports. Brugada pattern (8.1%) and Osborn wave (3.7%) were the other interesting findings. In multivariate analysis, when confounding factors were adjusted, myocardial infarction, atrioventricular conduction disturbances, sinus tachycardia, and the prolonged QTC > 500 msecond were four independent factors correlated with methanol toxicity severity measured with arterial blood PH on arterial blood gas measurements, with odds ratios of 12.82, 4.46, 2.32 and 3.15 (P < 0.05 for all), respectively. CONCLUSION: Electrocardiographic variations during methanol intoxication are remarkable and well-correlated with poisoning severity. Myocardial infarction was an egregious and yet a common concerning finding in this sample, which need to be ruled out in methanol toxicity.


Assuntos
Bloqueio Atrioventricular/induzido quimicamente , Cegueira/induzido quimicamente , Transtornos da Consciência/induzido quimicamente , Síndrome do QT Longo/induzido quimicamente , Metanol/envenenamento , Infarto do Miocárdio/induzido quimicamente , Solventes/envenenamento , Taquicardia Sinusal/induzido quimicamente , Adolescente , Adulto , Idoso , Bebidas Alcoólicas , Bloqueio Atrioventricular/sangue , Bloqueio Atrioventricular/fisiopatologia , Betacoronavirus , Cegueira/sangue , Cegueira/fisiopatologia , Gasometria , Síndrome de Brugada/sangue , Síndrome de Brugada/induzido quimicamente , Síndrome de Brugada/fisiopatologia , Transtornos da Consciência/sangue , Transtornos da Consciência/fisiopatologia , Infecções por Coronavirus , Eletrocardiografia , Feminino , Contaminação de Alimentos , Humanos , Concentração de Íons de Hidrogênio , Irã (Geográfico) , Síndrome do QT Longo/sangue , Síndrome do QT Longo/fisiopatologia , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Infarto do Miocárdio/sangue , Infarto do Miocárdio/fisiopatologia , Pandemias , Pneumonia Viral , Envenenamento/sangue , Envenenamento/fisiopatologia , Fatores Sexuais , Taquicardia Sinusal/sangue , Taquicardia Sinusal/fisiopatologia , Adulto Jovem
4.
J Anesth Hist ; 6(3): 166-167, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32921490

RESUMO

Urial K. Mayo (1816-1900) was a successful Boston dentist who was plagued by personal scandal. In 1883 he patented extending the duration of nitrous-oxide anesthesia with an alcoholic tincture of hops and poppies.


Assuntos
Anestesia Dentária/história , Anestésicos Inalatórios/história , Óxido Nitroso/história , Ópio/história , Anestésicos Inalatórios/química , Etanol/história , História do Século XIX , Humanos , Humulus , Papaver , Solventes/história , Estados Unidos
5.
Waste Manag ; 118: 139-149, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32892091

RESUMO

As an alternative to conventional plastic-waste treatments, herein, we report a pyrolytic plastic-recovery process in which diverse compounds and materials are recovered from the pyrolysis oil obtained from the plastic waste. Distillation of the pyrolysis oil led to a bitumen and a distilled fraction. The composition of the bitumen, as determined by saturate, aromatic, resin, and asphaltene (S.A.R.A.) analysis and corroborated by Fourier-transform infrared (FTIR) spectroscopy, was found to principally contain aromatics (55.05 wt%) and saturates (33.41 wt%), and has great potential as a modifier for bitumen mixtures by decreasing the viscosities or softening points of final products. The distilled fraction was characterised and compared to pyrolysis oil in terms of its physicochemical properties and composition. Analysis by gas-chromatography/mass-spectrometry (GC-MS) revealed high levels of aromatics, namely styrene, benzene, toluene, ethylbenzene, and α-methylstyrene, which are potentially recoverable base compounds for industrial use. With this in mind, the distillate was subjected to various processes, including aromatic extraction with sulfolane and subsequent fractional distillation to recover the principal compounds in the various GC-MS fractions. Fraction 1 was found to be rich in ethylbenzene and toluene, while fraction 2 contained 73.26 wt% styrene and was used to synthesise recycled polystyrene (PS), whose yield and molecular weight (Mw) were optimised by adjusting the initiator concentration, temperature, and time. The optimised recycled PS was characterised to provide a yield of 77.64% and a Mw higher than 53,000 g/mol; this recycled PS exhibited similar thermal properties to those of conventional PS prepared using petrochemical sources.


Assuntos
Plásticos , Poliestirenos , Hidrocarbonetos , Pirólise , Reciclagem , Solventes
6.
Waste Manag ; 118: 190-196, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32892095

RESUMO

The properties of infusibility and insolubility in organic solvent of cured epoxy resin makes it difficult to recycle carbon fiber reinforced plastics (CFRP). We have reported the recycling of CFRPs using the oxidizing power of hydroxyl radicals generated from NaOCl solution. In our study, we used benzyltrimethylammonium bromide (BTAB) and sodium dodecyl sulfate (SDS) for the interfacial separation between the epoxy resin and carbon fibers (CF). The surfactant system maximized recycling efficiency in both pretreatment and the main reaction of the CFRP recycling process. In the second step, the reaction time to successfully reclaim the CFs was much shorter, only one hour, compared with the two-hour reaction time for the non-SDS process previously reported by us. Scanning electron microscope images and Raman analyses showed that the surface of the reclaimed CF (r-CFs) was clean and smooth without any defects, and there was no significant structural change compared to virgin CF (v-CFs). The tensile strength of r-CF was 3.42 GPa which is 96.9% of the v-CF. Thus, the CFRP recycling process using SDS not only results in r-CF with good mechanical and physical properties, but also increases recycling efficiency by reducing the time.


Assuntos
Fibra de Carbono , Carbono , Reciclagem , Solventes , Tensoativos
7.
Environ Pollut ; 266(Pt 1): 115239, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32795887

RESUMO

Common solvents are frequently used as carriers to dissolve chemicals with a hydrophobic property that is extensively applied in the industrial and biomedical fields. In this study, we aimed to systematically study the sub-chronic effect of ten common solvents at low concentration exposure in adult zebrafish and perform neurobehavioral assessments for mechanistic exploration. After exposed to ten common solvents, including methanol, ethanol (EtOH), dimethyl sulfoxide (DMSO), isopropanol, acetone, polyethylene glycol-400 (PEG-400), glycerol, butanol, pentane, and tetrahydrofuran for continuous 10 day at 0.1% concentration level, adult zebrafish were subjected to perform a serial of behavioral tests, such as novel tank, mirror biting, predator avoidance, social interaction and shoaling. Later, 20 behavioral endpoints obtained from these five tests were transformed into a scoring matrix. Principal component analysis (PCA) and hierarchy clustering were performed to evaluate and compare the zebrafish behavior profiling. By using this phenomic approach, we were able to systematically evaluate the toxicity of the common solvents in zebrafish at a neurobehavioral level for the first time and found each common solvent-induced unique behavioral alteration to produce fingerprint-like patterns in hierarchy clustering and heatmap analysis. Among all tested common solvents, acetone and PEG-400 displayed better biocompatibility and less toxicity since they triggered less behavioral and biochemical alterations while methanol and DMSO caused severe behavior alterations in zebrafish after chronic exposure of these solvents. We conclude the behavioral phenomic approach conducted in this study providing a powerful tool to a systematical exploration of the common solvent toxicity at the whole organism level.


Assuntos
Fenômica , Peixe-Zebra , Acetona , Animais , Dimetil Sulfóxido , Solventes
8.
J Chromatogr A ; 1627: 461387, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823095

RESUMO

A simple and efficient magnetic solid-phase extraction (MSPE) method was established with magnetic covalent organic framework (COF) as adsorbent to enrich organophosphorus pesticides from fatty milk samples, followed by the sensitive determination via LC-MS/MS. The key parameters influencing the MSPE efficiency were comprehensively investigated to afford an optimized procedure. All the target analytes could be captured directly by magnetic COF from milk without protein precipitation, making the pretreatment rapid and convenient. Systematic method validation demonstrated its satisfactory linearity, recoveries (80.0-105 %), and precision (RSDs <12.3 %). The method limits of quantification were 0.2-0.5 µg L-1. A comparison experiment to the reported solid-phase extraction fully verified the present MSPE more rapid, accurate, and environment-friendly. Furthermore, FT-IR and XPS analysis were performed to reveal the adsorption mechanisms of magnetic COF to organophosphorus pesticides, which could offer guidance on the rational design of COF adsorbent for various target analytes.


Assuntos
Fenômenos Magnéticos , Estruturas Metalorgânicas/química , Leite/química , Compostos Organofosforados/análise , Praguicidas/análise , Extração em Fase Sólida/métodos , Acetonitrilos/análise , Adsorção , Animais , Limite de Detecção , Espectroscopia Fotoeletrônica , Padrões de Referência , Reprodutibilidade dos Testes , Solventes/química , Espectroscopia de Infravermelho com Transformada de Fourier
9.
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
10.
J Environ Manage ; 274: 111155, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32805472

RESUMO

This work reports on the potential application of UiO-66 in gas sweetening and its structural stability against water, air, dimethylformamide (DMF), and chloroform. The UiO-66 nanoparticles were solvothermally synthesized at different scales and activated via solvent exchange technique using chloroform, methanol, and ethanol. Thus prepared and aged MOFs were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and nitrogen adsorption-desorption analysis. The chloroform-activated MOF showed the largest surface area among all activation solvents, and presented high uptakes of 8.8 and 4.3 mmol/g for CO2 and CH4, respectively, at 298 K and 30 bar. This might be due to removing all unreacted organic ligands and DMF molecules from the pores of the framework. The UiO-66 nanoparticles are stable at the experimental conditions with no significant loss in crystalline structure and gas adsorption ability even after aging under different conditions for one year. The UiO-66 could be easily regenerated at 373 K with no observed significant reduction in gas uptakes even after five consecutive adsorption-desorption cycles. The present findings suggest the excellent potential of the UiO-66-derived MOFs as the promising materials for CO2/CH4 separation at low pressures and results can be applied in practical natural gas sweetening.


Assuntos
Poluentes Químicos da Água/análise , Água , Adsorção , Solventes , Difração de Raios X
11.
J Chromatogr A ; 1626: 461427, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32739066

RESUMO

The physicochemical properties of small molecules that can be determined by retention measurements in reversed-phase liquid chromatography include solvent-based properties inferred from equilibrium processes occurring predominantly in the mobile phase and sorption properties for materials which can be used as stationary phases inferred from solute-stationary phase interactions. In addition, physicochemical properties can be estimated from correlation models based on surrogate chromatographic systems with a similar capability for intermolecular interactions to the chemical or biological system. Examples of properties determined by direct methods include molecular descriptors (solvation parameter model), acid dissociation constants, formation constants, and surface properties of solids determined by inverse liquid chromatography. Examples of properties estimated by indirect methods include hydrophobicity, lipophilicity, n-octanol-water partition constant, soil-water sorption constant, non-specific toxicity to fish and microorganisms, and permeation coefficients for the blood-brain and skin-water barriers. Since all approaches depend on an accurate measurement of chromatographic retention parameters typical operational and mechanistic problems are discussed from the perspective of data quality. Fundamentally the accuracy of direct methods is limited by stationary phase heterogeneity and indirect methods by the limited number of suitable surrogate chromatographic models.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Cromatografia de Fase Reversa , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais , Octanóis/química , Solo/química , Solventes/química , Água/química
12.
J Chromatogr A ; 1626: 461370, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797849

RESUMO

Betacyanins, natural plant pigments, from Iresine herbstii Hook. ex Lindl. leaf extract were separated for the first time by high-speed countercurrent chromatography (HSCCC) in a highly polar solvent system composed of PrOH-ACN-(NH4)2SO4satd.soln-H2O (1.0:0.5:1.2:1.0; v/v/v/v) in the tail-to-head mode. The flow rate of the mobile phase was 2.0 ml/min and the column rotation speed was 860 rpm. The retention of the stationary phase was 81.0%. For the identification of separated betacyanins in the crude extract and in the HSCCC fractions, as well as for the molecular formulas and multi-step fragmentation pattern elucidation, liquid chromatography with tandem mass spectrometry and high-resolution ion-trap time-of-flight mass spectrometry were performed. The innovative application of the HSCCC system for fractionation of the betacyanins present in I. herbstii leaves enabled effective separation as well as preconcentration of the pigments for further low- and high-resolution LC-MS/MS analysis. HSCCC separation enabled identification of 22 betacyanins, of which 18 had not been detected previously in the leaves of I. herbstii, and four of these betacyanins (sinapoyl-gomphrenin and coumaroyl-gomphrenin as well as their epimers) were identified for the first time in the Iresine genus.


Assuntos
Amaranthaceae/química , Betacianinas/análise , Distribuição Contracorrente/métodos , Solventes/química , Amaranthaceae/metabolismo , Betacianinas/isolamento & purificação , Betacianinas/normas , Cromatografia Líquida de Alta Pressão/normas , Extratos Vegetais/química , Folhas de Planta/química , Folhas de Planta/metabolismo , Padrões de Referência , Espectrometria de Massas em Tandem/normas
13.
J Chromatogr A ; 1626: 461373, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797851

RESUMO

Simulation software for liquid chromatography can accelerate method development capabilities. In two-dimensional chromatography this is particularly attractive because there are more method variables to consider, provided simulations can account for the effects of injecting effluent from the first dimension separation into the second dimension column. In this paper we describe the adaptation of a previously described model (the Forssén model) to enable prediction of the profile of an injection pulse as it exits an Active Solvent Modulation (ASM) valve and enters the second dimension column under a variety of flow rate and sample loop size conditions (a global model). Experimentally measured injection profiles were used to train empirical models capable of generating injection profiles as a function of sample loop volume and flow rate. The resulting parameters were then used to generate an injection profile for a loop volume not used in the training set. The resulting profile agreed well with the experimentally obtained profile for this sample loop. Finally, chromatograms were simulated using previously developed simulation software incorporating the injection profile models developed in this work. Chromatographic peaks were simulated for valerophenone on an Agilent Zorbax Stablebond C18 stationary phase with an acetonitrile/water mobile phase gradient. Results of simulations based on experimental injection profiles, profiles predicted using the Forssén or global models, and rectangular injection profiles were compared. Comparison of the resulting chromatographic peaks revealed good agreement between those produced using experimental profiles or the Forssén or global models, with less than ± 0.3% deviations for retention times and less than ± 10% deviations for the peak widths (expressed as σ).


Assuntos
Cromatografia Líquida/métodos , Solventes/química , Acetonitrilos/química , Água/química
14.
J Chromatogr A ; 1626: 461377, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797853

RESUMO

This study reports the use ofa natural deep eutectic solvent (NADES) with hollow fiber-microporous membrane liquid-liquid microextraction (HF-MMLLE) for the multiclass determination of 11 compounds classified as emerging contaminantsin water. Different deep eutectic solvents were synthetized and Thymol: Camphor (1:1 molar fraction) wasused as extraction solvent. The Thymol:Camphor was impregnated into the polypropylene membrane porous for 10 min, replacing commonly used solvents (ex. hexane and octanol). The optimized parameters were obtained by multi and univariate models. Extractions were carried out for 50 min using 1.5 mL of water sample at pH 6 and without addition of salt while desorption was made in a mixture of acetone: methanol (3:1, v/v) for 15 min. Separation/quantification was conducted by HPLC with a diode array detection (DAD)and calibration curves were obtained for each analyte. Determination coefficients higher than 0.9906 and limits of detection ranged from 0.3 to 6.1 µg L-1. Intraday precision (n = 3) ranged from 1.6 to 18.4% and inter day from 5.0 to 21.3%. Relative recoveries were performed in tap and stream water and ranged from 64 to 123%.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Microextração em Fase Líquida/métodos , Solventes/química , Poluentes Químicos da Água/análise , Calibragem , Cromatografia Líquida de Alta Pressão/normas , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais , Polipropilenos/química , Porosidade , Espectrofotometria , Poluentes Químicos da Água/isolamento & purificação , Poluentes Químicos da Água/normas
15.
J Chromatogr A ; 1627: 461414, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823112

RESUMO

Various techniques have been evaluated for the extraction and cleanup of pesticides from environmental samples. In this work, a Selective Pressurized Liquid Extraction (SPLE) method for pesticides was developed using a Thermo Fisher Scientific Accelerated Solvent Extraction (ASE) system. This instrument was compared to the newly introduced (2017) extraction instrument, the Energized Dispersive Guided Extraction (EDGE) system, which combines Pressurized Liquid Extraction (PLE) and dispersive Solid Phase Extraction (dSPE). We first optimized the SPLE method using the ASE instrument for pesticide extraction from alfalfa leaves using layers of Florisil and graphitized carbon black (GCB) downstream of the leaf homogenate in the extraction cell (Layered ASE method). We then compared results obtained for alfalfa and citrus leaves with the Layered ASE method to those from a method in which the leaf homogenate and sorbents were mixed (Mixed ASE method) and to similar methods modified for use with EDGE (Layered EDGE and Mixed EDGE methods). The ASE and EDGE methods led to clear, colorless extracts with low residual lipid weight. No significant differences in residual lipid masses were observed between the methods. The UV-Vis spectra showed that Florisil removed a significant quantity of the light-absorbing chemicals, but that GCB was required to produce colorless extracts. Recoveries of spiked analytes into leaf homogenates were generally similar among methods, but in several cases, significantly higher recoveries were observed in ASE extracts. Nonetheless, no significant differences were observed among pesticide concentrations in field samples when calculated with the isotope dilution method in which labelled surrogates were added to samples before extraction. The extraction time with the ASE methods was ~45 minutes, which was ~4.5 times longer than with the EDGE methods. The EDGE methods used ~10 mL more solvent than the ASE methods. Based on these results, the EDGE is an acceptable extraction instrument and, for most compounds, the EDGE had a similar extraction efficiency to the ASE methods.


Assuntos
Técnicas de Química Analítica/métodos , Praguicidas/análise , Folhas de Planta/química , Solventes/química , Lipídeos/química , Medicago sativa/química , Resíduos de Praguicidas/análise , Extratos Vegetais/química , Espectrofotometria Ultravioleta
16.
J Chromatogr A ; 1627: 461416, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823114

RESUMO

Animal feeds are often reported to be contaminated with chemical residues, and when present above the maximum legal limit, these compounds can cause harmful effects to consumers of animal produce. Thus, animal feed safety is an important regulatory concern. The aim of this study was to optimise a multiresidue method for the simultaneous analysis of multi-class pesticides and a number of frequently used veterinary drugs using LC-MS/MS and GC-MS/MS. The method was validated in a range of feed matrices, including maize feed, poultry feed and mixed feed concentrate. The optimised sample preparation workflow involved extraction of feeds (5 g) with ethyl acetate (10 mL), followed by a freezing step (at -20°C) used for eliminating the matrix co-extractives. The extract was further cleaned by dispersive solid phase extraction with a combination of primary secondary amine, C18 and florisil sorbents. From the cleaned-extract, an aliquot was analysed by GC-MS/MS, while another portion of it was solvent-exchanged to acetonitrile:water (50:50) and then analysed by LC-MS/MS. This method effectively minimised the matrix interferences. A total of 192 pesticides was analysed by GC-MS/MS within a runtime of 22 min. The LC-MS/MS method was validated for 187 compounds including 17 veterinary drugs. For most of the compounds, the limit of quantification (LOQ) was 0.01 mg/kg. The recoveries at LOQ and higher levels ranged between 70% and 120%, with precision-RSDs of < 20%. The method provided a precise analysis in a wide range of market-feed samples. As shown, the method is suitable for regulatory and commercial testing purposes.


Assuntos
Ração Animal/análise , Cromatografia Líquida/métodos , Praguicidas/análise , Espectrometria de Massas em Tandem/métodos , Drogas Veterinárias/análise , Animais , Congelamento , Cromatografia Gasosa-Espectrometria de Massas , Limite de Detecção , Resíduos de Praguicidas/análise , Reprodutibilidade dos Testes , Solventes/química , Água/química
17.
J Chromatogr A ; 1627: 461421, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823116

RESUMO

Herein we present an efficient, column-switching method that relies on a custom-made T-union passive diffusion micromixer to assist water dilution and promote trap solute focusing of a high sample volume dissolved in pure organic solvent using a 0.075 mm i.d. nano-LC column. This method allows injecting 20 µL (or higher) of sample volume, speeding up the analysis time, with a 400-fold increase of the limits of quantitation for selected compounds. Five pesticides in different media were used as model compounds, and the analyses were carried out with a triple quadrupole mass spectrometer equipped with a Liquid Electron Ionization (LEI) LC-MS interface working in multiple reaction monitoring (MRM) mode. The system microfluidics were investigated using COMSOL modeling software. Robustness of the entire system was evaluated using a post-extraction addition soil extracts with limits of detection values spanning from 0.10 to 0.45 µg/L. Reproducible results in terms of peak area, peak shape, and retention times were achieved in soil matrix. Repeatability test on peak area variations were lower than 10%.


Assuntos
Cromatografia de Fase Reversa/métodos , Elétrons , Microfluídica/métodos , Nanopartículas/química , Espectrometria de Massas em Tandem/métodos , Água/química , Acetonitrilos/química , Difusão , Limite de Detecção , Praguicidas/análise , Reprodutibilidade dos Testes , Solventes/química
18.
J Chromatogr A ; 1627: 461430, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823119

RESUMO

There is a huge, still increasing market for synthetic and therapeutic peptides. Their quality control is commonly based on a generic reversed-phase liquid chromatography (RPLC) method with C18 stationary phase and acetonitrile gradient with 0.1% trifluoroacetic acid in the mobile phase. It performs exceptionally well for a wide variety of impurities, yet structurally closely related impurities with similar sequences, not resolved in preparative RPLC, may easily coelute in the corresponding QC run as well. To address this problem an advanced generic 2D-LC impurity profiling method was developed in this work. It employs a selective comprehensive (high resolution sampling) RP×RP 2D-LC separation using a 100×2.1 mm ID column with the common acidic generic gradient in the first dimension, while RPLC under basic pH on a short 30×3 mm ID column is used in the second dimension. Recording data with a UV detector at 215 nm after 1D separation provides the common generic 1D chromatogram. However, after the 2D separation a flow splitter enabled recording of the signals of complementary detectors comprising a diode array detector (DAD) in-line with a charged aerosol detector (CAD) and a quadrupole-time-of-flight (QTOF) mass spectrometer (MS) with an electrospray ionization (ESI) source. Generic conditions of this 2D-LC method have been established through optimization of 2D stationary and mobile phase considering different pH values and buffer concentrations. The orthogonal separation principle has been documented by a number of therapeutic peptides including Exenatide, Octreotide, Cyclosporine A and Oxytocin as well as some other proprietary synthetic peptides. The information density can be further enhanced by using the QTOF-MS detector by data independent acquisition with SWATH. Through this sequential window acquisition of all theoretical fragment ion mass spectra it became possible to collect MS/MS data comprehensively in the high-resolution sampling window, thus enabling the extraction of 2D-EICs from fragment ions and the generation of 2D-contour plots of all product ions. Using Oxytocin as an example for an important therapeutic peptide, the ability of this advanced generic sRP-UV×RP-DAD-CAD-ESI-QTOF-MS/MS method with SWATH for peptide quality control is discussed.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Cromatografia de Fase Reversa/métodos , Peptídeos/análise , Acetonitrilos/química , Tampões (Química) , Concentração de Íons de Hidrogênio , Ocitocina/análise , Controle de Qualidade , Solventes/química , Espectrometria de Massas em Tandem
19.
J Chromatogr A ; 1626: 461345, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797825

RESUMO

Modern liquid-liquid chromatography mainly refers to the following two kinds of chromatographic apparatuses: countercurrent chromatography based on hydrodynamic equilibrium systems and centrifugal partition chromatography based on hydrostatic equilibrium systems. In this paper, the recent advancements in enantioseparations by liquid-liquid chromatography, including the separation mechanism, chiral selector, two-phase solvent system, methods to improve the peak resolution and recent applications, are reviewed. The future outlook for liquid-liquid chromatography in enantioseparations is also proposed.


Assuntos
Cromatografia Líquida/métodos , Algoritmos , Distribuição Contracorrente , Concentração de Íons de Hidrogênio , Ligantes , Solventes/química , Estereoisomerismo
20.
J Chromatogr A ; 1626: 461308, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797813

RESUMO

The Wayne State University (WSU) experimental descriptor database is utilized to bench mark the current capability of the solvation parameter model for use as a quantitative structure-retention relationship tool for estimating retention in gas and reversed-phase liquid chromatography. The prediction error for the retention factors of varied compounds on six open-tubular columns for gas chromatography (Rtx-5 SIL MS, DB-35 ms, RtxCLPesticides, HP-88, HP-INNOWAX and SLB-IL76) and three packed columns for reversed-phase liquid chromatography (SunFire C18, XBridge Shield RP18, and XBridge Phenyl) is used to establish expectations related to current practices. Each column data set was divided into a training set for calibration and a test set for validation employing a roughly 1 to 2 split, such that each test set contained about 40 to 80 varied compounds. The average absolute error for the prediction of retention factors by gas chromatography varied from about 0.1 to 0.4 on the retention factor scale with the larger error typical of stationary phases ranked as the most polar (or cohesive). For reversed-phase liquid chromatography the average error for the prediction of retention factors was 0.3 to 0.5 and generally larger than for gas chromatography. Statistical filters where utilized to identify a group of polycyclic aromatic compounds without hydrogen-bonding functional groups with a larger prediction error on the SunFire C18 column than for other compounds of smaller size, flexible structure or containing hydrogen-bonding functional groups. The heterogeneity of the retention mechanism is speculated to be the main contribution to the prediction error for both gas and liquid chromatography using the solvation parameter model.


Assuntos
Cromatografia Gasosa/métodos , Cromatografia de Fase Reversa/métodos , Ligação de Hidrogênio , Cinética , Solventes/química
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