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1.
J Agric Food Chem ; 67(31): 8689-8699, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31298525

RESUMO

The contamination of honey with hepatotoxic pyrrolizidine alkaloids (PAs) is an actual concern for food safety. This study reports the first application of dispersive liquid-liquid microextraction (DLLME) in the determination of five relevant PAs, and the relative N-oxide derivatives (PANOs), in honey. The effects of different experimental parameters (pH, ionic strength, type and volume of DLLME solvents) affecting the extraction efficiency were carefully investigated and optimized. PAs were extracted from honey (diluted solution 10% w/v at pH 9.5) by injecting a mixture of chloroform and isopropyl alcohol. A reduction step (zinc powder in acidic aqueous solution) before DLLME was performed to convert PANOs in PAs and to obtain the total PA levels. Both sample preparation protocols (DLLME and Zn-DLLME) showed negligible matrix effects on PA signal intensity in honeys of different botanical origins. The overall recoveries of DLLME and Zn-DLLME ranged from 71 to 102% and from 63 to 103%, respectively, with a good precision (standard deviations in the range from 1 to 12%). The attained method quantification limits stayed between 0.03 and 0.06 µg kg-1, and the linear response range extended to 25 µg kg-1. Additionally, the proposed method provides results comparable to those of the SPE protocol in the analysis of real samples. An analysis of retail honeys revealed PA residues in all analyzed samples, with a maximum level of 17.5 µg kg-1 (total PAs). Globally, the proposed method provides a sensitive and accurate determination of analytes and offers numerous advantages, such as simplicity, low cost, and a high sample throughput, which make it suitable for screening and quality control programs in food chain and occurrence studies.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Contaminação de Alimentos/análise , Mel/análise , Microextração em Fase Líquida/métodos , Alcaloides de Pirrolizidina/química , Alcaloides de Pirrolizidina/isolamento & purificação , Espectrometria de Massas em Tandem/métodos
2.
J Chromatogr A ; 1602: 117-123, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31229251

RESUMO

The use of miniaturized systems with the possibility for automation has become increasingly popular in the field of bioanalysis. As a new approach to liquid phase microextraction in the 96-well format, parallel artificial liquid membrane extraction (PALME) was introduced in 2013. In the present work, the reliability of the quantitative data obtained with PALME was thoroughly evaluated. Amitriptyline, nortriptyline, quetiapine, venlafaxine, o-desmethylvenlafaxine, and fluoxetine were selected as model analytes. The analytes were extracted under non-exhaustive conditions from human plasma samples and the extracts were analyzed directly by LC-MS/MS. Accuracy was within ±15% and precision was <15% when the QC samples were prepared in both pooled plasma and in plasma from multiple sources. Accuracy and precision was superior when stable isotopically labelled (SIL) internal standards were used, as compared to structural analogue internal standards in the plasma samples from multiple sources. SIL internal standards are therefore recommended as the first choice. Assessment of accuracy and precision was also carried out with four different operators performing the extraction procedure, providing accuracy within ±15% and precision <15%. The extraction recoveries were in the range from 48 to 85 %, and non-exhaustive extraction of the analytes did not affect the accuracy and precision of the method. With the method described, up to 96 samples can be extracted with a total extraction time of 60 min and with a total consumption of organic solvent less than 0.4 mL for the whole wellplate. PALME is therefore a new approach to high-throughput sample preparation, providing accurate quantification, along with simple workflow, low consumption of organic solvent, and extensive sample clean-up.


Assuntos
Microextração em Fase Líquida/métodos , Preparações Farmacêuticas/sangue , Calibragem , Cromatografia Líquida , Humanos , Marcação por Isótopo , Membranas Artificiais , Controle de Qualidade , Padrões de Referência , Reprodutibilidade dos Testes , Espectrometria de Massas em Tandem
3.
Anal Bioanal Chem ; 411(20): 5023-5031, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31177332

RESUMO

A simple method to determine hazardous silver nanoparticles (AgNPs) based on ionic liquid (IL) dispersive liquid-liquid microextraction and back-extraction is described. This approach involves AgNP stabilization using a cationic surfactant followed by extraction from the sample matrix by means of an IL as an extraction phase. Certain ILs have high affinity for metals, and preliminary experiments showed that those ILs consisting of imidazolium cation efficiently extracted AgNPs in the presence of a cationic surfactant and a chelating agent. Afterward, histamine was used as a dispersing agent to promote phase transfer of differently coated AgNPs from the IL in aqueous solution to be subsequently analyzed by UV-visible spectrometry. The analytical procedure allows AgNPs to be recovered from the sample matrix in an aqueous medium, the enrichment factor being up to 4, preserving both AgNP size and AgNP shape as demonstrated by transmission electron microscopy images and the localized surface plasmon resonance band characteristic of each AgNP. The present method exhibited a linear response for AgNPs in the range from 3 to 20 µg/mL, the limit of detection being 0.15 µg/mL. Method efficiency was assessed in spiked orange juice and face cream, yielding recoveries ranging from 75.7% to 96.6%. The method was evaluated in the presence of other nanointerferents (namely, gold nanoparticles). On the basis of diverse electrophoretic mobilities and surface plasmon resonance bands for metal nanoparticles, capillary electrophoresis was used to prove the lack of interaction of the target AgNPs with gold nanoparticles during the whole protocol; thus, interferents do not affect AgNP determination. As a consequence, the analytical approach described has great potential for the analysis of engineered nanosilver in consumer products. Graphical abstract Simple protocol for the determination of silver nanoparticles (AgNPs) based on dispersive liquid-liquid extraction with a specific short alkyl side chain ionic liquid and their quantitative detection with a UV-visible spectrometer. HMIM•PF6 1-hexyl-3-methylimidazolium hexafluorophosphate, NP nanoparticle, SPR surface plasmon resonance.


Assuntos
Cosméticos/química , Sucos de Frutas e Vegetais/análise , Líquidos Iônicos/química , Microextração em Fase Líquida/métodos , Nanopartículas Metálicas/análise , Prata/química , Artefatos , Estudos de Viabilidade , Limite de Detecção , Nanopartículas Metálicas/química , Espectrofotometria Ultravioleta/métodos , Ressonância de Plasmônio de Superfície
4.
J Agric Food Chem ; 67(28): 8045-8052, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31241326

RESUMO

n-Octadecylamine was adopted as a cleanup agent to develop a novel solidification of a switchable solvent-based QuEChERS method. At higher temperatures (such as 55 °C), n-octadecylamine can melt into a liquid, allowing effective extraction of matrix interferences in acetonitrile solution (i.e., in dispersive liquid-liquid microextraction). At lower temperatures, n-octadecylamine carrying matrix interferences can rapidly solidify and easily separate from the acetonitrile solution. The results demonstrated that n-octadecylamine possessed a better ability to remove matrix interferences and reduce matrix effects than those of traditional solid-phase dispersive extraction cleanup agents of primary secondary amine and octadecyl bonded silica gel. By coupling it with gas chromatography-mass spectrometry, the proposed method was applied to the detection of 16 pesticides in cucumber. The recoveries were from 80.9 to 112.6% with relative standard deviations less than 12.9%. Satisfactory results were also obtained for the detection of 16 pesticides in pear, orange, apple, pepper, lettuce, and tomato.


Assuntos
Frutas/química , Microextração em Fase Líquida/métodos , Resíduos de Praguicidas/química , Resíduos de Praguicidas/isolamento & purificação , Verduras/química , Acetonitrilos/química , Aminas/química , Citrus sinensis/química , Cucumis sativus/química , Cromatografia Gasosa-Espectrometria de Massas , Alface/química , Microextração em Fase Líquida/instrumentação , Lycopersicon esculentum/química , Malus/química , Solventes/química
5.
Food Chem ; 293: 378-386, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151625

RESUMO

Considering the negative impacts on human health and the environment, determinations of arsenic (As) and antimony (Sb), is of unquestionable importance. The present study describes the development of innovative and practical deep eutectic solvent (DES) based vortex assisted microextraction (DES-VAME) method for preconcentration of As and Sb from environmental waters, honey and rice prior to analysis by hydride generation-atomic absorption spectrometry (HG-AAS). The use of As(III) and Sb(III) in presence of dithizone at pH 10.5 by means of donor-acceptor mechanism were decided as analytes. Total As and Sb were determined after reduction process. The analytical properties obtained following optimization were as follows. Limit of detection (LOD), precision (as RSD%), recoveries and enhancement factor for As and Sb were calculated as 7.5 ng L-1/15.6 ng L-1, 2.1% /2.7%, 93.5%/96.2% and 104/85, respectively. Following validation with certified reference material, the method was successfully applied to the analysis of real samples.


Assuntos
Antimônio/isolamento & purificação , Arsênico/isolamento & purificação , Análise de Alimentos/métodos , Microextração em Fase Líquida/métodos , Antimônio/análise , Arsênico/análise , Análise de Alimentos/instrumentação , Contaminação de Alimentos/análise , Mel/análise , Concentração de Íons de Hidrogênio , Limite de Detecção , Microextração em Fase Líquida/instrumentação , Oryza/química , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Solventes/química , Espectrofotometria Atômica/métodos , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/isolamento & purificação
6.
J Chromatogr A ; 1603: 401-406, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31122729

RESUMO

Phenols in tobacco smoke can adversely affect health with serious consequences that include cardiovascular toxicity, tumor promotion and genotoxic activity. Hence, an improved method involving in situ acetylation and dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for the determination of 39 phenols in mainstream tobacco smoke (MTS). The in situ acetylation was optimized using four protocols, after which the effects of experimental variables on acetylation efficiency were studied using a multifactorial experimental design. The optimum conditions were found to involve an initial 75 µL volume of acetic anhydride, 140 mg of NaHCO3 and 72 mg of K2CO3. The phenolic acetates were then subjected to DLLME, after which they were identified and quantified by GC-MS. A total of 32 additional phenols were tentatively identified. Good linearity was observed with R > 0.999 and each lack-of-fit P > 0.05. The relative recoveries were in the range of 94.8-104.3% with repeatabilities and reproducibilities less than 5.5% and 6.8%, respectively. The limits of detection ranged from 1.12 to 1.74 ng cig-1, with high enrichment factors between 87 and 144. This method was applied to the MTS from three commercial cigarettes with different tar levels. The results provide valuable information for assessing the risks of phenols.


Assuntos
Cromatografia Gasosa-Espectrometria de Massas/métodos , Microextração em Fase Líquida/métodos , Fenóis/análise , Poluição por Fumaça de Tabaco/análise , Acetilação , Limite de Detecção , Padrões de Referência , Reprodutibilidade dos Testes , Solventes/química
7.
J Chromatogr A ; 1600: 95-104, 2019 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-31056271

RESUMO

Halogen bonding (XB) was here proposed, for the first time, as a solubilization mechanism for increasing efficiency in the liquid-liquid microextraction of halogenated compounds. The approach was illustrated by the extraction of hexabromocyclododecane (HBCD) enantiomers in natural waters with a supramolecular solvent (SUPRAS) made up of inverted hexagonal aggregates of decanoic acid. The XB and dispersion interactions offered by the SUPRAS were able to extract the six HBCD enantiomers (i.e. (+)-α-, (-)-α- (+)-ß-, (-)-ß-, (+)-γ- and (-)-γ-) quantitatively (e.g. recoveries in the range 89-106%) and reach concentration factors as high as 720 without the need for solvent evaporation. HBCD enantiomers in the SUPRAS extract were directly analysed by chiral liquid chromatography coupled to tandem mass spectrometry (LCMS/MS). Quantitation limits of the method (0.09-0.9 ng L-1) were below the quality standard stablished by the European Union for HBCDs in inland surface water samples (1.6 ng L-1), and the precision, expressed as relative standard deviation (n = 6), was below 9% for all the HBCD enantiomers at concentrations within the range 50-500 ng L-1. The method was successfully applied to the enantioselective determination of HBCDs in the dissolved and the particle-bound fractions of river waters containing different concentration of suspended particles (10-57.8 mg L-1) that were spiked at two concentration levels (10 and 100 ng L-1). The results here obtained prove that XB is a valuable mechanism for the solubilisation of halogenated compounds that can effectively increase their recovery from liquid and solid samples.


Assuntos
Monitoramento Ambiental/métodos , Hidrocarbonetos Bromados/isolamento & purificação , Microextração em Fase Líquida/métodos , Rios/química , Poluentes Químicos da Água/isolamento & purificação , Cromatografia Líquida , Halogênios/química , Hidrocarbonetos Bromados/química , Solventes/química , Estereoisomerismo , Espectrometria de Massas em Tandem , Poluentes Químicos da Água/análise
8.
J Chromatogr A ; 1600: 87-94, 2019 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-31060784

RESUMO

In this paper, poly m-aminophenol/nylon 6/graphene oxide (PmAP/N6/GO) electrospun nanofiber was fabricated and applied as an efficient sorbent for thin film microextraction (TFME) of phthalate esters (PAEs). The porosity, morphology, wettability, solvent stability and chemical structure of the prepared nanofiber were evaluated. The prepared PmAP/N6/GO nanofiber film exhibited some prominent advantages such as large surface area, porous fibrous structure, high stability, good hydrophilicity and excellent extraction efficiency. Afterward, thin film microextraction-gas chromatography-mass spectroscopy (TFME-GC-MS) method was developed for the quantitative analysis of PAEs, and the effective parameters on the extraction performance were investigated systematically. At the optimal operating conditions, the large linearity range (0.5-250 ng mL-1) with excellent correlation coefficient (<0.998) had been acquired for this method. Moreover, low limits of detection (LODs) (0.1-0.15 ng mL-1) exhibited the satisfactory sensitivity of the proposed method. Finally, the TFME-GC-MS method was successfully utilized for the measurement of PAEs in milk solutions and drinking water preserved in baby bottle with satisfactory relative recoveries (RRs) (88-101%) and relative standard deviations (RSDs) lower than 8.0% (n = 3). Totally, a simple, rapid, sensitive and highly efficient method was introduced to analyze trace PAEs in complex samples.


Assuntos
Ésteres/isolamento & purificação , Microextração em Fase Líquida/métodos , Leite/química , Nanofibras/química , Água/química , Aminofenóis/química , Animais , Caprolactama/análogos & derivados , Caprolactama/química , Ésteres/análise , Ésteres/química , Cromatografia Gasosa-Espectrometria de Massas , Grafite/química , Interações Hidrofóbicas e Hidrofílicas , Limite de Detecção , Ácidos Ftálicos/química , Polímeros/química , Poluentes Químicos da Água/análise
9.
Anal Bioanal Chem ; 411(16): 3447-3461, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31123783

RESUMO

This study aimed to determine simultaneously five major street cocaine adulterants (caffeine, lidocaine, phenacetin, diltiazem, and hydroxyzine) in human urine by dispersive liquid-liquid microextraction (DLLME) and high-performance liquid chromatography. The chromatographic separation was obtained in gradient elution mode using methanol:water plus trifluoroacetic acid 0.15% (v/v) (pH = 1.9) at 1 mL min-1 as mobile phase, at 25 °C, detection at 235 nm, and analysis time of 20 min. The effect of major DLLME operating parameters on extraction efficiency was explored using the multifactorial experimental design approach. The optimum extraction condition was set as 4 mL human urine sample alkalized with 0.5 M sodium phosphate buffer (pH 12), NaCl (15%, m/v), 300 µL acetonitrile (dispersive solvent), and 800 µL chloroform (extraction solvent). Linear response (r2 ≥ 0.99) was obtained in the range of 180-1500 ng mL-1 with suitable selectivity, quantification limit (180 ng mL-1), mean recoveries (33.43-76.63%), and showing relative standard deviation and error (within and between-day assays) ≤15%. The analytes were stable after a freeze-thaw cycle and a short-term room temperature stability test. This method was successfully applied in real samples of cocaine users, suggesting that our study may contribute to the appropriate treatment of cocaine dependence or with the cases of cocaine acute intoxication.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Cocaína/urina , Microextração em Fase Líquida/métodos , Drogas Ilícitas/urina , Cafeína/normas , Cafeína/urina , Humanos , Hidroxizina/normas , Hidroxizina/urina , Lidocaína/normas , Lidocaína/urina , Limite de Detecção , Fenacetina/normas , Fenacetina/urina , Padrões de Referência , Reprodutibilidade dos Testes , Drogas Ilícitas/normas
10.
J Chromatogr Sci ; 57(6): 575-581, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31095673

RESUMO

The human body's vitamin D levels are determined by measuring the level of 25-hydroxy-vitamin D3 (25-OH-vitamin D3) in human serum. In this research, a fast, simple, efficient and highly sensitive low-density solvent based on dispersive liquid-liquid microextraction (DLLME) was employed for the successful determination of 25-OH-vitamin D3 from complex human serum matrices. Reversed phase high-performance liquid chromatography was used as a powerful technique. The important parameters in the low-density solvent-DLLME method were optimized using response surface methodology based on central composite design. The calibration curves displayed a high level of linearity (R2 > 0.997) for 25-OH-vitamin D3 in the range of 2-500 ng mL-1. The limit of detection and limit of quantitation were 0.6 ng mL-1 and 1.9 ng mL-1, respectively. The relative standard deviation for the seven analyses was 7.1%. The relative recoveries of vitamin D3 in spiked human serum samples were between 85% and 97%. The amount of 25-OH-vitamin D3 in samples was determined using the proposed method and acceptable results were reported.


Assuntos
25-Hidroxivitamina D 2/sangue , Cromatografia Líquida de Alta Pressão/métodos , Cromatografia de Fase Reversa/métodos , Microextração em Fase Líquida/métodos , 25-Hidroxivitamina D 2/isolamento & purificação , Humanos , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes , Projetos de Pesquisa
11.
Environ Monit Assess ; 191(5): 287, 2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-31001697

RESUMO

Solvent-terminated dispersive liquid-liquid microextraction (ST-DLLME) as a simple, fast, and low-cost technique was developed for simultaneous extraction of Cd2+ and Cu2+ ions in aqueous solutions. Multiobjective evolutionary algorithm based on decomposition with the aid of artificial neural networks (ANN-MOEA/D) was used for the first time in chemistry, environment, and food sciences to optimize several independent variables affecting the extraction efficiency, including disperser volume and extraction solvent volume, pH, and salt addition. To perform the ST-DLLME operations, xylene, methanol, and dithizone were utilized as an extraction solvent, disperser solvent, and chelating agent, respectively. Non-dominated sorting genetic algorithm versions II and III (NSGA II and NSGA III) as multiobjective metaheuristic algorithms and in addition central composite design (CCD) were studied as comparable optimization methods. A comparison of results from these techniques revealed that ANN-MOEA/D model was the best optimization technique owing to its highest efficiency (97.6% for Cd2+ and 98.3% for Cu2+). Under optimal conditions obtained by ANN-MOEAD, the detection limit (S/N = 3), the quantitation limit(S/N = 10), and the linear range for Cu2+ were 0.05, 0.15, and 0.15-1000 µg L-1, respectively, and for Cd2+ were 0.07, 0.21, and 0.21-750 µg L-1, respectively. The real sample recoveries at a spiking level of 0.05, 0.1, and 0.3 mg L-1 of Cu2+ and Cd2+ ions under the optimal conditions obtained by ANN-MOEA/D ranged from 94.8 to 105%.


Assuntos
Cádmio/química , Cobre/análise , Águas Residuárias/análise , Poluentes Químicos da Água/análise , Algoritmos , Quelantes/química , Monitoramento Ambiental/métodos , Íons , Limite de Detecção , Microextração em Fase Líquida/métodos , Metanol/química , Redes Neurais (Computação) , Solventes/química , Água/química
12.
J Chromatogr B Analyt Technol Biomed Life Sci ; 1118-1119: 109-115, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-31030103

RESUMO

A rapid and eco-friendly method was developed to extract and pre-concentrate sulfonamides (sulfadiazine, sulfamerazine and sulfadimethoxine) from chicken meat before high-performance liquid chromatographic analysis. The method involved rapid microwave-assisted extraction with hydrochloric acid (pH = 5), further solid phase purification using HLB cartridge and 5% ammonium hydroxide, and homogeneous liquid-liquid microextraction using hexanoic acid as switchable hydrophilicity solvent. The overall time required for sample preparation was 10 min and the volume of organic solvent used for extraction was only 200 µL. The method exhibited good linearity (r2 > 0.9941), low limits of detection (2.5-6.0 ng/g) and allowed quantification of target sulfonamides spiked at levels of 50-400 ng/g in chicken meat with spiked recoveries in the range of 94.1%-112.0%.


Assuntos
Microextração em Fase Líquida/métodos , Carne/análise , Sulfonamidas/análise , Sulfonamidas/isolamento & purificação , Animais , Galinhas , Cromatografia Líquida de Alta Pressão/métodos , Resíduos de Drogas , Interações Hidrofóbicas e Hidrofílicas , Limite de Detecção , Modelos Lineares , Micro-Ondas , Reprodutibilidade dos Testes
13.
Talanta ; 199: 329-335, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30952267

RESUMO

Nowadays, developing new methods for the effective extraction/separation of drugs (present at trace levels) from complicated matrices (as biological fluids) is certainly a great challenge for many operators. In this regard, green-based agarose gel electromembrane extraction (G-EME) was for the first time combined with dispersive liquid-liquid microextraction (DLLME) toward G-EME/DLLME methodology (i.e., tandem extraction approach). Two basic drugs such as trimipramine (TRI) and clomipramine (CLO) extracted from the urine samples, were used as model compounds. Regarding method workflow, analytes were extracted from the 5 mL sample, through a synthesized agarose gel membrane, to the 700 µL aqueous acceptor phase under the optimized conditions (pH of acceptor phase: 2.0; pH of gel membrane: 2.0; pH of donor phase: 4.0, voltage value: 30 V, and extraction time: 25 min). In the next step, acceptor solution was poured to a conic vial and mixed with 100 µL alkaline solution (NaOH, 1 M). Afterwards, DLLME procedure took place again at optimal conditions, i.e., extraction solvent was carbon tetrachloride (10 µL), and dispersive solvent was acetone (100 µL). Ultimately, gas chromatography (GC) was applied for the detection and quantification of drugs. Such G-EME/DLLME configuration has brought two main advantages. Firstly, interferences such as proteins and other large biological molecules were eliminated from biological fluids via G-EME. Further, high enrichment factors (EFs of 260-370 refer to extraction recoveries of 52-74%) were obtained using DLLME with acceptable detection limits (1.0-3.0 ng mL-1). Finally, the suggested approach was successfully utilized to determine drugs at trace levels in urine samples.


Assuntos
Clomipramina/urina , Microextração em Fase Líquida/métodos , Sefarose , Trimipramina/urina , Cromatografia Gasosa , Géis/síntese química , Géis/química , Humanos , Concentração de Íons de Hidrogênio , Sefarose/síntese química , Sefarose/química
14.
An Acad Bras Cienc ; 91(suppl 1): e20180294, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31017188

RESUMO

Green Analytical Chemistry (GAC) is a research field that seeks for more sustainable analytical approaches to minimize the toxicity and amounts of wastes without hindering the analytical performance. This is a trend in Analytical Chemistry worldwide and because of the diversity of innovations on this subject, Brazil stands out as the third in the list of the main contributors to GAC, with ca. 11.2% of the published articles. Significant innovations and interesting applications in several fields have been presented and Brazil is continuously moving from Chemistry to Green Chemistry also in the Analytical Chemistry field. Selected contributions for sample preparation, spectro- and electroanalysis, separation techniques, chemometrics, and also procedures for point-of-care measurements are critically reviewed.


Assuntos
Técnicas de Química Analítica/tendências , Química Verde/tendências , Pesquisa/tendências , Brasil , Técnicas de Química Analítica/métodos , Química Verde/métodos , Humanos , Microextração em Fase Líquida/métodos , Microextração em Fase Líquida/tendências , Microextração em Fase Sólida/métodos , Microextração em Fase Sólida/tendências , Solventes , Análise Espectral/métodos , Análise Espectral/tendências
15.
Ecotoxicol Environ Saf ; 178: 130-136, 2019 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-31002967

RESUMO

A simple, effective and convenient method for determination of phenolic compounds by acid-base induced deep eutectic solvents (DESs) microextraction was developed. The binary and ternary DESs were prepared by a range of fatty acids (C8-C12), which can act as hydrogen bond donors and hydrogen bond acceptors simultaneously. The gas-assisted mixing customization provides excellent mixing performance and concentration efficiency through the bubble adsorption mechanism for the handling of large-volume aqueous sample. In extraction process, NH3·H2O can act as the emulsifier agent and reacted with DESs to form salts with a cloudy solution, which can obviously improve the extraction efficiency. HCl can act as the phase separation agent, and there is no need to centrifuge, which increases the efficiency of analysis procedure. The factors affected on extraction efficiency were carefully optimized. At optimum conditions and molar ratio of C8:C9:C12 (3:2:1), the limit of detections (LODs), the preconcentration factor, the repeatability (RSDs%) were in the range of 0.22-0.53 µg L-1, 235-244, and 2.6-6.7%, respectively. Finally, the proposed method was applied to analyze four phenolic compounds in real water samples and the recoveries were between 87.4% and 106.6%.


Assuntos
Ácidos Graxos/química , Química Verde/métodos , Microextração em Fase Líquida/métodos , Fenóis/análise , Solventes/química , Poluentes Químicos da Água/análise , Adsorção , Limite de Detecção , Modelos Teóricos , Água/química
16.
Bull Environ Contam Toxicol ; 102(6): 848-853, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30989280

RESUMO

In this study, the detection power of a gas chromatography mass spectrometer (GC-MS) for procymidone and chlorflurenol was significantly enhanced using switchable solvent liquid phase microextraction (SS-LPME) as a preconcentration tool. This was achieved by a comprehensive optimization of significant parameters to the SS-LPME method such as switchable solvent amount, concentration and amount of sodium hydroxide, pH effect and mixing effect. The optimum experimental conditions obtained were used to determine analytical figures of merit for the analytes. The limits of detection obtained were 0.44 and 2.9 ng/mL for procymidone and chlorflurenol, respectively. The optimum method was applied to water sampled from an irrigation canal and two wastewater samples. The samples were spiked at two concentrations and the percent recovery results obtained ranged between 86 and 115% for both analytes. The recovery results together with the low standard deviations recorded validated the method as accurate and precise.


Assuntos
Compostos Bicíclicos com Pontes/análise , Fluorenos/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Irrigação Agrícola , Compostos Bicíclicos com Pontes/química , Fluorenos/química , Cromatografia Gasosa-Espectrometria de Massas/métodos , Microextração em Fase Líquida/métodos , Solventes/química , Água/química
17.
Food Chem ; 286: 500-505, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-30827638

RESUMO

A switchable solvent based liquid phase microextraction (SS-LPME) has been proposed for the determination of cobalt in egg yolk and Vitamin B12 at trace levels. N,N-Dimethylbenzylamide (DMBA) was used as a switchable solvent and converted to protonated DMBA form by the addition of dry ice. Cobalt was complexed with 1,5-diphenylcarbazone (DPC) and extracted into the DMBA phase. After the extraction, HNO3 was added to increase nebulization efficiency of the DMBA phase. Slotted quartz tube (SQT) was combined with FAAS to enhance the detection power of the system when compared to the conventional FAAS. Under the optimum conditions, limit of detection values were recorded as 75 µg L-1 for FAAS, 33 µg L-1 for SQT-FAAS, 7.6 µg L-1 for SS-LPME-FAAS, and 2.3 µg L-1 for SS-LPME-SQT-FAAS. The developed method was applied for the determination of cobalt in egg yolk and Vitamin B12 and the recovery results were found in the range of 105-114% with 0.30-7.6 standard deviation values (n = 3).


Assuntos
Cobalto/análise , Gema de Ovo/química , Microextração em Fase Líquida/métodos , Solventes/química , Espectrofotometria Atômica/métodos , Vitamina B 12/análise , Limite de Detecção , Quartzo/química , Semicarbazonas/química , Poluentes Químicos da Água/análise
18.
J Chromatogr A ; 1597: 46-53, 2019 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-30926256

RESUMO

A simple, rapid, and effective analytical procedure for determining three triazole fungicides (myclobutanil, epoxiconazole, and tebuconazole) in water samples is developed by high-performance liquid chromatography-diode array detection after evaporation-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic droplets. The extraction procedure involves the sequential addition of the extraction solvent 1-dodecanol (low density), volatile solvent dichloromethane (high density), and calcium oxide to the aqueous sample (the latter reacting exothermically). The CaO reaction can promote the volatilization of the dichloromethane which disperses the 1-dodecanol as fine droplets in the aqueous sample due to the bubbles generated. Therefore, a dispersive solvent is not required. Then, the floating 1-dodecanol is solidified using an ice bath for easy separation from the sample. The variables (the volumes of extraction and volatile solvents, amounts of calcium oxide and sodium chloride, pH values, and extraction time) in the extraction procedure are further optimized. Under optimized conditions, the linearity ranges are 0.05-5 µg mL-1 with correlation coefficients greater than 0.99. The limits of detection and quantification are 0.0051-0.0090 µg mL-1 and 0.0169-0.0299 µg mL-1, respectively. The recoveries of myclobutanil, epoxiconazole, and tebuconazole in tap, reservoir, and river water range between 77.6% and 104.4% with relative standard deviations ranging from 0.6% to 7.8%. Hence, the method was reliable for analysis of myclobutanil, epoxiconazole, and tebuconazole in water samples.


Assuntos
Cromatografia Líquida de Alta Pressão , Monitoramento Ambiental/métodos , Água Doce/química , Fungicidas Industriais/análise , Microextração em Fase Líquida/métodos , Triazóis/análise , Solventes/análise
19.
Food Chem ; 286: 141-145, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-30827587

RESUMO

The concentration of tetramethylpyrazine (TMP) in vinegar is an active indicator of vinegar quality. Dispersive liquid-liquid microextraction (DLLME) was first applied to vinegar as a clean-up pre-treatment for the rapid (5 min) determination of TMP by high-pressure liquid chromatography with ultraviolet detection (HPLC-UV), and may serve as an alternative to solid-phase extraction (SPE) or solid-phase microextraction (SPME). High sensitivity of HPLC for TMP determination was obtained using the DLLME pretreatment, with a limit of detection (LOD) of 0.001 mg L-1 and limit of quantification (LOQ) of 0.005 mg L-1. The developed method exhibited excellent linearity in the concentration range of 0.050-80.000 mg L-1, with a correlation coefficient R2 > 0.999. Furthermore, the percentage recovery of TMP in vinegar using the developed method was within the range 97.97-105.24%. Therefore, DLLME coupled with HPLC-UV is a sensitive and promising method for vinegar clean-up and TMP assay.


Assuntos
Análise de Alimentos/métodos , Microextração em Fase Líquida/métodos , Pirazinas/análise , Ácido Acético/análise , Cromatografia Líquida de Alta Pressão/métodos , Limite de Detecção , Sensibilidade e Especificidade
20.
Food Chem ; 286: 185-190, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-30827594

RESUMO

An in-situ chemical reaction based dispersive procedure termed as CO2-effervescence assisted emulsification microextraction was first utilized for pre-concentration of Sudan dyes in spices. It is simple, quick, and efficient; based on a switchable fatty acid (hexanoic acid, pKa ∼ 4.8). The extraction agent is able to be switched into hydrophobic/hydrophilic forms in pH-changeable media, leading to facile and effective dispersion and phase's separation. The method was proved by the analysis of spiked samples. Optimization was statistically performed, resulted in maximum extraction efficiencies. Under optimal conditions, method validation was assayed in the aqueous solutions. Wide linearity with high R2 values and low detection limits (1-5 ng mL-1) were obtainable. Also, enrichment factors were 62-66 with proper repeatability (%RSDs < 6.8, n = 3). Good validations in terms of recovery (86.6-104.5%) and repeatability (%RSDs < 7.8, n = 3, C = 15 and 30 µg g-1) in foodstuffs confirmed a great effectiveness of the method in complex matrices.


Assuntos
Compostos Azo/análise , Cromatografia Líquida de Alta Pressão/métodos , Análise de Alimentos/métodos , Microextração em Fase Líquida/métodos , Especiarias/análise , Dióxido de Carbono/química , Emulsões/química , Ácidos Graxos/química , Contaminação de Alimentos/análise , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Limite de Detecção , Reprodutibilidade dos Testes , Solventes/química
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