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1.
J Chromatogr A ; 1609: 460445, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31431357

RESUMO

The separation of 14 chiral sulfoxides was systematically studied on 12 cellulose-based chiral columns in acetonitrile and acetonitrile-water mobile phases. Out of all monosubstituted methylphenylcarbamates of cellulose the one having a methyl moiety in position 3 showed more universal chiral resolving ability compared to 2- and 4-substituted derivatives. Out of disubstituted phenylcarbamates of cellulose the ones with methyl substituents showed higher enantiomer resolving ability compared to chloro-substituted ones and substitution in positions 3 of the phenyl moiety was clearly advantageous. From disubstituted derivatives those possessing a combination of methyl- and chloro-substituents were advantageous compared to the ones having dimethyl- or dichloro-substituents. Chiral recognition ability of most chiral selectors towards studied sulfoxides was higher in pure acetonitrile compared to previously studied methanol. The effect of water addition to the mobile phase on analyte retention and enantioseparation was also quite different from that observed with methanol. In particular, with aqueous methanol by increasing the water content in the mobile phase retention increased in most cases and the separation factor improved. In contrast, with aqueous acetonitrile retention and separation factors decreased up to a certain water content in the mobile phase and then started to recover again for most of the studied analytes.


Assuntos
Acetonitrilos/química , Celulose/química , Cromatografia Líquida de Alta Pressão/métodos , Sulfóxidos/química , Sulfóxidos/isolamento & purificação , Água/química , Metanol/química , Fenilcarbamatos/química , Estereoisomerismo
2.
J Chromatogr A ; 1609: 460458, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31443969

RESUMO

Pentacyclic triterpenoids (PCTs) possess high biological activity, including antitumor, anti-inflammatory, antiviral and hepatoprotective properties and are widespread in a plant biomass. Due to significant differences in polarity and other physicochemical properties, the simultaneous determination of different classes of PCTs by the methods of reversed phase liquid chromatography is difficult. In the present study, we proposed a new approach to chromatographic separation of such compounds based on the use of a stationary phase with a mixed retention mechanism combining hydrophobic, weak anion exchange and hydrophilic interactions. The use of the Acclaim Mixed-Mode WAX-1 column and tuning the selectivity by changing the contributions of different types of analyte-stationary phase interactions allowed the separation of 10 PCTs (betulin, erythrodiol, uvaol, friedelin, lupeol, ß-amyrin, α-amyrin, betulinic, oleanolic and ursolic acids) belonging to four different classes (monools, diols, ketones and triterpenic acids) during 7.5 min in isocratic elution mode. The combination of this approach with atmospheric pressure chemical ionization tandem mass spectrometric detection and pressurized liquid extraction of analytes with methanol allowed to develop a rapid, accurate and highly sensitive method for analyzing PCTs in plant tissues with a total duration of the analytical cycle (including sample preparation steps) of not more than 40 min. It provides the detection limits in plant biomass extracts of 3-12 µg L-1 (44 µg L-1 for friedelin). The developed method was validated and successfully tested in the analyses of real birch bark and lingonberry peels.


Assuntos
Cromatografia Líquida/métodos , Triterpenos Pentacíclicos/isolamento & purificação , Espectrometria de Massas em Tandem/métodos , Acetonitrilos/química , Betula/química , Biomassa , Calibragem , Formiatos/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Concentração Osmolar , Triterpenos Pentacíclicos/química , Extratos Vegetais/química , Reprodutibilidade dos Testes , Vaccinium vitis-Idaea/química
3.
J Chromatogr A ; 1609: 460427, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31439441

RESUMO

Multi-linear gradients are a convenient solution to get separation of complex samples by modulating carefully the gradient slope, in order to accomplish the local selectivity needs for each particular solute cluster. These gradients can be designed by trial-and-error according to the chromatographer experience, but this strategy becomes quickly inappropriate for complex separations. More evolved solutions imply the sequential construction of multi-segmented gradients. However, this strategy discards part of the search space in each step of the construction and, again, cannot deal properly with very complex samples. When the complexity is too large, the only valid alternative for finding the best gradient is the use of global search methods, such as genetic algorithms (GAs). Recently, a new global approach where the level of detail is increased along the search has been proposed, namely Multi-scale optimisation (MSO). In this strategy, cubic splines are applied to build intermediate curves to define any arbitrary solvent variation function. Subdivision schemes are used to generate the cubic splines and control their level of detail. The search was subjected to a number of restrictions, such as avoiding long elution and favouring a balanced peak distribution. The aim of this work is evaluating and comparing the results of GAs and MSO. Both approaches were tested with a set of 14 diuretics and probenecid, eluted with acetonitrile-water mixtures using a C18 column. Satisfactory baseline resolution was obtained with an analysis time of 15-16 min. We found that GAs optimisation offered results equivalent to those provided by MSO, when the penalisation parameters were included in the cost function.


Assuntos
Algoritmos , Cromatografia de Fase Reversa/métodos , Diuréticos/isolamento & purificação , Acetonitrilos/química , Solventes , Água/química
4.
J Chromatogr A ; 1609: 460446, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31420178

RESUMO

Two new copolymer-grafted silica stationary phases were prepared and employed in hydrophilic interaction chromatography (HILIC). 2-(Dimethylamino)ethyl methacrylate (DMAEMA) are copolymerized with itaconic acid (IA) and acrylic acid (AA) respectively, via thiol-ene click reaction on silica surface with deep eutectic solvents (DES) as new solvents. The obtained poly(DMAEMA-co-itaconic acid)-grafted silica (Sil-PDM-PIA) and poly(DMAEMA-co-acrylic acid)-grafted silica (Sil-PDM-PAA) were characterized by Fourier transform infrared spectroscopy, elemental analysis and solid-state 13C NMR spectra. Their hydrophilic interaction performances were evaluated by separating nucleosides, nucleobases, saccharides, and amino acids. Compared with previous reported poly(itaconic acid)-grafted silica (Sil-PIA) and poly(acrylic acid)-grafted silica (Sil-PAA) stationary phases, these two new copolymer-grafted silica performed higher selectivity and better separation for polar analytes in HILIC.


Assuntos
Cromatografia/métodos , Química Click/métodos , Interações Hidrofóbicas e Hidrofílicas , Polímeros/química , Dióxido de Silício/química , Solventes/química , Compostos de Sulfidrila/química , Acetonitrilos/química , Aminoácidos/isolamento & purificação , Entropia , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Metacrilatos/química , Nucleosídeos/isolamento & purificação , Nylons/química , Reprodutibilidade dos Testes , Sais/química , Espectroscopia de Infravermelho com Transformada de Fourier , Succinatos/química , Temperatura Ambiente
5.
Talanta ; 206: 120180, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31514886

RESUMO

A novel analytical approach is proposed to discriminate between solid biopsies of chromophobe renal cell carcinoma (chRCC) and renal oncocytoma (RO). The method comprises the following steps: (i) ultrasonic extraction of proteins from solid biopsies, (ii) protein depletion with acetonitrile, (iii) ultrasonic assisted in-solution digestion using magnetic nanoparticle with immobilized trypsin, (iv) C18 tip-based preconcentration of peptides, (v) sequential extraction of the peptides with ACN, (vi) MALDI-snapshot of the extracts and (vii) investigation of the extract containing the most discriminating features using high resolution mass spectrometry. With this approach we have been able to differentially cluster renal oncocytoma and chromophobe renal cell carcinoma and identified 18 proteins specific to chromophobe and seven unique to renal oncocytoma. Chromophobes express proteins associated with ATP function (ATP5I & 5E; VATE1 & G2; ADT2), glycolysis (PGK1) and neuromedin whilst oncocytomas express ATP5H, ATPA, DEPD7 and TRIPB thyroid receptor interacting protein.


Assuntos
Adenoma Oxífilo/diagnóstico , Biomarcadores Tumorais/análise , Carcinoma de Células Renais/diagnóstico , Neoplasias Renais/diagnóstico , Rim/química , Fragmentos de Peptídeos/análise , Proteínas/análise , Acetonitrilos/química , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Biomarcadores Tumorais/química , Biomarcadores Tumorais/isolamento & purificação , Biópsia , Diagnóstico Diferencial , Enzimas Imobilizadas/química , Feminino , Humanos , Rim/patologia , Nanopartículas de Magnetita/química , Masculino , Camundongos , Pessoa de Meia-Idade , Proteínas/química , Proteínas/isolamento & purificação , Proteômica/métodos , Extração em Fase Sólida/métodos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Tripsina/química , Ondas Ultrassônicas
6.
J Chromatogr Sci ; 57(9): 769-777, 2019 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-31504301

RESUMO

Acetamide is a potential genotoxic impurity; it should control in drug substance based on daily dosage level. It forms from base-contaminated acetonitrile and by-product of some drug substances. The available methods for acetamide in drug substance and water samples were determined by GC-MS using internal standard with critical procedures. These developed and validated methods can assist in evaluating the reaction between acetonitrile and different bases and also determine trace level acetamide in drug substances. The method development was initiated with DB-624, 30 m, 0.32 width and 1.0-µm column. The column was used to validate at the 600 ppm TTC value. Similarly, the CP-SIL 5CB, 60 m, 0.32 width, the 5-µm column was used for the remaining TTC values. The validation study was performed for all TTC limits. The % RSD for precision at 600, 60, 20, 10 and 2.5 ppm was <15%. The % recovery at all TTC level was in between the 70 and 130%. Solution stability study was performed up to the 24 h. At 2.5 ppm, the results were <15% variation from the initial value. The linearities from the 50 to 150% concerning TTC values were more than limit of 0.98 correlation coefficient. The limit of detection and limit of quantitation values were 0.4 to the 1.3 ppm, respectively, for 2.5 ppm TTC limit method.


Assuntos
Acetamidas/análise , Acetonitrilos/análise , Contaminação de Medicamentos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Preparações Farmacêuticas/química , Acetamidas/química , Acetonitrilos/química , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes
7.
BMC Res Notes ; 12(1): 492, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31391088

RESUMO

OBJECTIVE: Comparison was done between high-performance liquid chromatography (HPLC) and a competitive enzyme-linked immunosorbent assay (ELISA) for detection and quantification of aflatoxin B1 (AFB1) in feed samples. The two procedures were standardized and validated before the actual experiment. Five concentrations (0, 5, 10, 20 and 30 ppb) of feed samples were used for both methods. For the HPLC technique, the samples were extracted in acetonitrile/water (90/10) solution, cleaned-up using solid phase extraction (SPE) column, and derivatized by water/trifluoroacetic acid/glacial acetic acid (35/10/5) solution before instrument analysis. The samples were extracted in 70% methanol for the ELISA technique. RESULTS: The two tests showed very strong linearity with correlation coefficient value of > 0.99 using standard solutions. The mean recovery rate was 92.42% (with relative standard deviation (RSD) of 5.97) and 75.64% (RSD = 34.88) for HPLC and ELISA, respectively. There was no statistically significant difference in recovery rate between the two methods. There was a positive correlation (r = 0.84) between them which indicated that the two techniques can be used to detect and quantify aflatoxin B1 in feed samples. However, there were variations among replicates for the ELISA method, which shows that this method is more applicable for screening purposes.


Assuntos
Aflatoxina B1/isolamento & purificação , Cromatografia Líquida de Alta Pressão/normas , Ensaio de Imunoadsorção Enzimática/normas , Contaminação de Alimentos/análise , Zea mays/química , Acetonitrilos/química , Ração Animal/análise , Animais , Cromatografia Líquida de Alta Pressão/métodos , Ensaio de Imunoadsorção Enzimática/métodos , Etanol/química , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Extração em Fase Sólida/métodos , Solventes/química , Água/química
8.
J Pharm Biomed Anal ; 175: 112788, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31382116

RESUMO

During the HPLC related substances testing of pregabalin API, an unknown peak was observed at a level exceeding the identification threshold. Preliminary investigation revealed that this impurity is not a process impurity but rather an artifactual solution degradant or "ghost peak" during the HPLC analysis. By using a strategy that combines LC-PDA/UV-MSn with mechanism-based stress studies, the unknown peak was rapidly identified as a covalent adduct formed between pregabalin and acetonitrile (the latter is a component of the HPLC sample diluent), which is structurally an ethylamidine derivative of pregabalin. It appeared that the formation of this solution degradant was catalyzed by alkaline impurities during the sample preparation. This plausible mechanism was verified by a mechanism-based forced degradation study, in which a base was added into the sample diluent and consequently, the pregabalin-acetonitrile adduct was produced extremely efficiently at a level of ˜92%. Subsequently, the structure of the solution degradant was confirmed as an ethylamidine derivative of pregabalin through characterization by 1D and 2D NMR; the formation of the ethylamidine moiety is apparently via a nucleophilic attack on the cyano group of acetonitrile by the amino group of pregabalin. Due to the extensive presence of primary and secondary amine moieties in drug substances, this kind of artifactual solution degradation would likely occur during the sample preparations of these amine drugs in their HPLC analyses. In a GMP environment, such an event would trigger undesirable out-of-specification (OOS) investigations. The results of this study should help resolve such OOS investigations or prevent their happening from the very beginning. Furthermore, the somewhat surprising finding of the rather facile reaction that produces the ethylamidine moiety using simple alkylnitrile reagents, such as acetonitrile, may be of practical value in the synthesis of alkylamidines.


Assuntos
Acetonitrilos/química , Pregabalina/química , Soluções/química , Aminas/química , Catálise , Química Farmacêutica/métodos , Cromatografia Líquida de Alta Pressão/métodos , Contaminação de Medicamentos , Excipientes/química , Espectroscopia de Ressonância Magnética/métodos
9.
J Pharm Pharmacol ; 71(10): 1508-1519, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31373700

RESUMO

OBJECTIVE: To investigate the effect of formulation parameters on the preparation of transfersomes as sustained-release delivery systems for lidocaine and to develop and validate a new high-performance liquid chromatography (HPLC) method for analysis. METHOD: Taguchi design of experiment (DOE) was used to optimise lidocaine-loaded transfersomes in terms of phospholipid, edge activator (EA) and phospholipid : EA ratio. Transfersomes were characterised for size, polydispersity index (PDI), charge and entrapment efficiency (%EE). A HPLC method for lidocaine quantification was optimised and validated using a mobile phase of 30%v/v PBS (0.01 m) : 70%v/v Acetonitrile at a flow rate of 1 ml/min, detected at 255 nm with retention time of 2.84 min. The release of lidocaine from selected samples was assessed in vitro. KEY FINDINGS: Transfersomes were 200 nm in size, with PDI ~ 0.3. HPLC method was valid for linearity (0.1-2 mg/ml, R2 0.9999), accuracy, intermediate precision and repeatability according to ICH guidelines. The %EE was between 44% and 56% and dependent on the formulation parameters. Taguchi DOE showed the effect of factors was in the rank order : lipid : EA ratio Ëƒ EA type Ëƒ lipid type. Optimised transfersomes sustained the release of lidocaine over 24 h. CONCLUSION: Sustained-release, lidocaine-loaded transfersomes were successfully formulated and optimised using a DOE approach, and a new HPLC method for lidocaine analysis was developed and validated.


Assuntos
Anestésicos Locais/química , Preparações de Ação Retardada/química , Acetonitrilos/química , Química Farmacêutica/métodos , Cromatografia Líquida de Alta Pressão/métodos , Lidocaína/química , Lipossomos/química , Tamanho da Partícula , Fosfolipídeos/química
10.
J Chromatogr A ; 1608: 460414, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31416623

RESUMO

The mismatch of elution strength between the sample diluent and the eluent causes undesirable peak deformations for large sample volumes in gradient liquid chromatography. The solution to that problem consists in diluting the sample solution in a weak solvent. But the minimum dilution factor has to be determined by the user given some performance objectives. In silico approaches are applied in this work to find such adequate dilution factors. Two calculations methods are proposed for the prediction of peak distortions. The first comprehensive method is based on solving numerically the mass balance equations for all the analytes and the strong solvent. An excellent agreement between the experimental and the calculated gradient chromatograms is observed (sample diluent: acetonitrile/water, 50/50, v/v; injection volume: 15 µL; linear gradient: 5%-95% acetonitrile during 3 min) for five compounds (acetanilide, coumarin, benzoin, bi-naphthol, and dibutylphthalate) injected into a 2.1 × 50 mm column packed with 1.7 µm XBridge-C18 particles. This first method happens to be highly time-consuming and impractical for common users. Experimental work and calculation times are then minimized by applying a second method based on the basics of retention and dispersion of injected pulses. Despite being less accurate than the first method, the agreement between the experimental and calculated peak width remains physically meaningful allowing the experimenter to rapidly guess the required sample dilution factor for any combination of injected volume and strong solvent concentration in the sample solution.


Assuntos
Cromatografia Líquida/instrumentação , Acetonitrilos/química , Simulação por Computador , Indicadores e Reagentes , Solventes/química , Água/química
11.
J Chromatogr A ; 1605: 460372, 2019 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-31402106

RESUMO

The present work describes the preparation of two ionic liquid and carboxyl acid silane reagents via photo-initiated thiol-ene click chemistry that have been bonded to silica to afford two mixed-mode stationary phases (Sil-C4Im-C9Co and Sil-C9Im-C4Co). The two stationary phases provided satisfactory retention repeatability and efficiencies. The influence of acetonitrile content, salt concentration and pH of the mobile phase was investigated to clarify the retention properties of the prepared stationary phases. The results showed that the prepared Sil-C4Im-C9Co and Sil-C9Im-C4Co undergo multiple interactions with solutes under different chromatographic conditions. The retention mechanisms were further studied by the linear energy solvation relationship and Van't Hoff plots. Finally, the stationary phases were employed to separate hydrophobic solutes (alkylbenzenes and polycyclic aromatic hydrocarbons) under reversed phase liquid chromatography (RPLC) mode, hydrophilic solutes (carboxylic acids, nucleosides and bases) under hydrophilic interaction liquid chromatography (HILIC) mode and inorganic anions under ion-exchange chromatography (IEC) mode, providing excellent performance and varying selectivity when compared with a commercial column. The bonding method in this work is feasible and the prepared stationary phases are promising when employed in RPLC/HILIC/IEC mixed-mode chromatography applications.


Assuntos
Cromatografia por Troca Iônica/métodos , Cromatografia de Fase Reversa/métodos , Interações Hidrofóbicas e Hidrofílicas , Líquidos Iônicos/química , Acetonitrilos/química , Animais , Ânions , Benzeno/análise , Ácidos Carboxílicos/análise , Química Click , Concentração de Íons de Hidrogênio , Leite/química , Nucleosídeos/análise , Reprodutibilidade dos Testes , Sais/química , Dióxido de Silício/química , Termodinâmica , Triazinas/análise
12.
Molecules ; 24(15)2019 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-31366025

RESUMO

In the present work, we developed a simple and rapid sample preparation method for the determination of neonicotinoid pesticides in honey based on the matrix-induced sugaring-out. Since there is a high concentration of sugars in the honey matrix, the honey samples were mixed directly with acetonitrile (ACN)-water mixture to trigger the phase separation. Analytes were extracted into the upper ACN phase without additional phase separation agents and injected into the HPLC system for the analysis. Parameters of this matrix-induced sugaring-out method were systematically investigated. The optimal protocol involves 2 g honey mixed with 4 mL ACN-water mixture (v/v, 60:40). In addition, this simple sample preparation method was compared with two other ACN-water-based homogenous liquid-liquid extraction methods, including salting-out assisted liquid-liquid extraction and subzero-temperature assisted liquid-liquid extraction. The present method was fully validated, the obtained limits of detection (LODs) and limits of quantification (LOQs) were from 21 to 27 and 70 to 90 µg/kg, respectively. Average recoveries at three spiked levels were in the range of 91.49% to 97.73%. Precision expressed as relative standard deviations (RSDs) in the inter-day and intra-day analysis were all lower than 5%. Finally, the developed method was applied for the analysis of eight honey samples, results showed that none of the target neonicotinoid residues were detected.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Mel/análise , Inseticidas/isolamento & purificação , Extração Líquido-Líquido/métodos , Neonicotinoides/isolamento & purificação , Acetonitrilos/química , Cromatografia Líquida de Alta Pressão/normas , Análise de Alimentos , Contaminação de Alimentos , Humanos , Limite de Detecção , Variações Dependentes do Observador , Reprodutibilidade dos Testes , Solventes/química , Água/química
13.
Molecules ; 24(15)2019 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-31366033

RESUMO

The adsorption of lithium ions(Li+) and the separation of lithium isotopes have attracted interests due to their important role in energy storage and nuclear energy, respectively. However, it is still challenging to separate the Li+ and its isotopes with high efficiency and selectivity. A novel cellulose-based microsphere containing crown ethers groups (named as MCM-g-AB15C5) was successfully synthesized by pre-irradiation-induced emulsion grafting of glycidyl methacrylate (GMA) and followed by the chemical reaction between the epoxy group of grafted polymer and 4'-aminobenzo-15-crown-5 (AB15C5). By using MCM-g-AB15C5 as adsorbent, the effects of solvent, metal ions, and adsorption temperature on the adsorption uptake of Li+ and separation factor of 6Li/7Li were investigated in detail. Solvent with low polarity, high adsorption temperature in acetonitrile could improve the uptake of Li+ and separation factor of lithium isotopes. The MCM-g-AB15C5 exhibited the strongest adsorption affinity to Li+ with a separation factor of 1.022 ± 0.002 for 6Li/7Li in acetonitrile. The adsorption isotherms in acetonitrile is fitted well with the Langmuir model with an ultrahigh adsorption capacity up to 12.9 mg·g-1, indicating the unexpected complexation ratio of 1:2 between MCM-g-AB15C5 and Li+. The thermodynamics study confirmed the adsorption process is the endothermic, spontaneous, and chemisorption adsorption. As-prepared novel cellulose-based adsorbents are promising materials for the efficient and selective separation of Li+ and its isotopes.


Assuntos
Celulose/química , Éteres de Coroa/química , Lítio/isolamento & purificação , Radioisótopos/isolamento & purificação , Acetonitrilos/química , Adsorção , Eletricidade , Compostos de Epóxi/química , Metacrilatos/química , Microesferas , Energia Nuclear , Termodinâmica
14.
J Chromatogr A ; 1607: 460403, 2019 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-31378523

RESUMO

MOF-1210(Zr/Cu) is a new heterometallic cluster-based metal-organic framework material as well as a promising solid phase extraction coating material with ordered spatial structure, permanent high porosity and large specific surface area. In this work, a novel MOF-1210(Zr/Cu) modified magnetic nanoparticles (MNPs) was successfully prepared for magnetic solid phase extraction (MSPE) of benzophenones, including 2,4-dihydroxybenzophenone (BP-1), 2-hydroxy-4-methoxybenzophenone (BP-3) and 2,2',4,4'-tetrehydroxybenzophenone (BP-6). The MOF-1210(Zr/Cu)-MNPs were synthesized in one step by a simple solvothermal method and showed high extraction efficiency towards analytes (with enrichment factors of 91-122). The extraction mechanism studies showed that the hydrogen bond interaction and coordination interaction between MOF-1210(Zr/Cu) and BPs played important roles during the extraction process. By coupling with HPLC, the MOF-1210(Zr/Cu)-MNPs-based MSPE-HPLC method showed wide linear range (0.1-300.0 ng·mL-1), good linearity (R ≥ 0.9982), excellent reproducibility (RSD ≤ 3.60%) and remarkable sensitivity (LODs in the range of 0.01-0.02 ng·mL-1). This method was also successfully applied to the extraction and detection of benzophenones in soil samples. Good recoveries were obtained (87.6%-113.8%) with RSDs less than 11.12%, which demonstrated the practicality of the proposed method.


Assuntos
Benzofenonas/análise , Cobre/química , Nanopartículas de Magnetita/química , Estruturas Metalorgânicas/química , Solo/química , Extração em Fase Sólida/métodos , Zircônio/química , Acetonitrilos/química , Ácidos/química , Adsorção , Concentração de Íons de Hidrogênio , Limite de Detecção , Reprodutibilidade dos Testes , Cloreto de Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Fatores de Tempo
15.
J Chromatogr A ; 1602: 397-408, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31285058

RESUMO

In reversed-phase liquid chromatography, the performance for basic compounds is affected by the interaction of the protonated (cationic) species with the anionic free silanols on the alkyl-bonded stationary phases. Using aqueous-organic mobile phases in the absence of additives, the retention may be too high, and the peaks be broad and asymmetric. The performance is improved by addition to the mobile phase of ionic liquids, from which 1-hexyl-3-methylimidazolium chloride ([C6MIm][Cl]) has especially good characteristics. A recent report has also revealed that the use of the phosphate system as buffer, at varying concentration and pH, may have a significant role in the chromatographic performance of basic compounds, with effects on both retention and peak shape. In this work, this study has been extended to other three buffer systems (acetate, citrate, and formate), at increasing concentrations and pH 3 and 7, in the presence and absence of [C6MIm][Cl]. The results have been compared with those obtained with the phosphate system. The retention increases by addition of larger concentration of all buffers, in both absence and presence of [C6MIm][Cl]. Without additive, peak performance is also enhanced significantly. This effect is minimal in the presence of [C6MIm][Cl], which yields highly symmetrical peaks at all buffer concentrations, due to an effective blocking of the silanol activity.


Assuntos
Boratos/química , Cromatografia de Fase Reversa/métodos , Imidazóis/química , Acetonitrilos/química , Antagonistas Adrenérgicos beta/análise , Tampões (Química) , Cromatografia Líquida de Alta Pressão/métodos , Concentração de Íons de Hidrogênio , Líquidos Iônicos/química , Solventes , Água/química
16.
Environ Sci Pollut Res Int ; 26(25): 25874-25882, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31273652

RESUMO

Up-flow biological activated carbon (UBAC) filter has been widely used in waterworks due to its less hydraulic loss, stronger biodegradation ability, and the prevention of excessive biomass growth relative to down-flow BAC treatment. In this study, the different removal efficiency (DRE) of disinfection byproduct precursors between dichloroacetonitrile (DCAN) and dichloroacetamide (DCAcAm) was evaluated when UBAC filter was used as advanced treatment process. Results showed that the UBAC filter with approximately 36 months of usage time had a poor performance in the removal of DCAcAm formation potential (FP) (i.e. 9.3-19.1%) compared to DCAN FP (i.e., 22.5-34.1%). After chlorination of UBAC effluent, the hydrolysis of DCAN to form DCAcAm only partly contributed to the DRE variations of both DCAN FP and DCAcAm FP. Using the high-throughput sequencing technology and the redundancy analysis (RDA), the second dominant genus Bacillus in UBAC filter, which may transform precursors of DCAN into inorganic matters, could be another reason that led to the DRE in DCAN and DCAcAm FP. The formation and leakage of soluble microbial products (SMPs) was identified by excitation-emission matrix (EEM) peak intensities as well as variation of biological index (BIX). The SMPs released into UBAC effluent, favoring the formation of DCAcAm, also contributed to the precursors of both DCAN and DCAcAm, causing a poor removal performance in DCAcAm FP by UBAC filter.


Assuntos
Acetamidas/análise , Acetonitrilos/análise , Carvão Vegetal/química , Desinfecção/métodos , Acetamidas/química , Acetonitrilos/química , Biodegradação Ambiental , Halogenação
17.
Pak J Pharm Sci ; 32(3): 981-986, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31278710

RESUMO

Polymorphism occurs in pharmaceutical compounds affect to the physicochemical quality and goal of therapy. Thus, quality evaluation of different crystal forms should be assessed especially the solubility and dissolution behaviors among polymorphic forms, which correlate to bioavailability and therapy efficacy. To achieved the different of a polymorph various solvent were used such as acetonitrile, methanol, ethyl acetate, acetone, water, n-hexane, and n-heptane. All of the crystal modification resulted were characterized by a polarization light microscopy (PLM), Fourier-Transform Infrared (FTIR) differential scanning calorimetry (DSC) and powdered X-ray diffraction (PXRD). Besides that, nature of solubility in water (24 and 48 hours test times) and particulate dissolution profile (an hour test) were carried out. There were various polymorphs success resulted and have significant differences in morphology, definite spectral fingerprints, crystal structure and thermal behavior. From the solubility of the samples found the top three highest soluble forms i.e. Form 6, 2 and 3, respectively. But there are showed became in order reverse performance after 60 minutes dissolution (Form 3, 2 and 6, respectively). The polymorphic forms of EFV were successful to obtained by the solvents treatment. Therefore, the physicochemical properties of polymorphic forms from active pharmaceutical ingredients (APIs) should be carefully considered in dosage forms pre-formulation approaches.


Assuntos
Benzoxazinas/química , Solventes/química , Acetona/química , Acetonitrilos/química , Varredura Diferencial de Calorimetria , Cristalização , Hexanos/química , Metanol/química , Microscopia de Polarização , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química , Difração de Raios X
18.
Biomed Chromatogr ; 33(11): e4666, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31353507

RESUMO

Knowledge of the acid-base dissociation constants of drugs is the key to understanding their biopharmaceutical characteristics. In the present work, the effect of pH and organic modifiers (acetonitrile and methanol) was investigated in the determination of dissociation constants (pKa ) of nine representative drugs (atenolol, betahistine, clarithromycin, deferiprone, diclofenac, ibuprofen, metoprolol, naproxen and propranolol) using reversed-phase thin-layer chromatography. Mobile phase consisting of various buffers and methanol-acetonitrile (10, 20, 30, 40, 50 and 60%, v/v) was used to evaluate the retention pattern on reversed-phase plates. Compared with methanol, acetonitrile gave better results for the experimentally determined pKa values by extrapolation to zero organic modifier volume fractions. To assess the effectiveness of the developed method the results were correlated using principal component analysis and hierarchical cluster analysis. The calculated values of the aqueous dissociation constant were compared with those reported previously using potentiometry and capillary electrophoresis and also with different computational platforms like ACD/Lab, ChemAxon and Jchem calculator. The results obtained by the RPTLC method were in good agreement with potentiometric methods for pKa determination.


Assuntos
Cromatografia de Fase Reversa/métodos , Cromatografia em Camada Delgada/métodos , Preparações Farmacêuticas/análise , Preparações Farmacêuticas/química , Solventes/química , Acetonitrilos/química , Simulação por Computador , Concentração de Íons de Hidrogênio , Metanol/química , Modelos Químicos
19.
Food Chem ; 300: 125200, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31325748

RESUMO

Ethyl carbamate (EC) and N-nitrosoamines (NAs) are toxic contaminants which can be typically formed in fermented alcoholic beverages. In the present work, a novel approach for simultaneous analysis of EC and NAs in beer and yellow rice wine based on ice-bath assisted sodiumhydroxide purification and GC-MS/MS was firstly established. Samples were extracted with acetonitrile-ethyl acetate after addition of internal standards. The extraction solution system was purified by sodiumhydroxide solid under ice-bath. After concentration, target analytes were separated on a HP-INNOWAX quartz capillary column and determined under dynamic multiple reactions monitoring mode of MS/MS. The limits of detection and quantification (LOD and LOQ), matrix effect, recovery and precision of the method were evaluated. Results were linear in the concentration range 2-200 µg/L for all analytes of interest, with regression coefficients higher than 0.999. LODs and LOQs were in the ranges of 0.1-0.5 µg/kg and 0.5-1.5 µg/kg, respectively. The mean recoveries at three spiked levels were between 81.5% and 121.0%. The intra- and inter-day precisions were in the ranges of 2.2-9.4% and 1.6-7.9%, respectively. The validated method was successfully applied to determine thirteen targets in commercial beer and yellow rice wine. EC was detected in all beers and yellow rice wines with the concentrations ranging from 1.18 to 22.90 µg/L. Results indicated wide EC contamination and confirmed its urgency for monitoring EC in fermented alcoholic beverages.


Assuntos
Cerveja/análise , Contaminação de Alimentos/análise , Nitrosaminas/análise , Uretana/análise , Vinho/análise , Acetonitrilos/química , Fracionamento Químico/métodos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Gelo , Limite de Detecção , Oryza , Reprodutibilidade dos Testes , Hidróxido de Sódio/química , Espectrometria de Massas em Tandem/métodos
20.
Molecules ; 24(12)2019 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-31213011

RESUMO

Cyclic lipodepsipeptides or CLiPs from Pseudomonas are secondary metabolites that mediate a wide range of biological functions for their producers, and display antimicrobial and anticancer activities. Direct interaction of CLiPs with the cellular membranes is presumed to be essential in causing these. To understand the processes involved at the molecular level, knowledge of the conformation and dynamics of CLiPs at the water-lipid interface is required to guide the interpretation of biophysical investigations in model membrane systems. We used NMR and molecular dynamics to study the conformation, location and orientation of the Pseudomonas CLiP viscosinamide in a water/dodecylphosphocholine solution. In the process, we demonstrate the strong added value of combining uniform, isotope-enriched viscosinamide and protein NMR methods. In particular, the use of techniques to determine backbone dihedral angles and detect and identify long-lived hydrogen bonds, establishes that the solution conformation previously determined in acetonitrile is maintained in water/dodecylphosphocholine solution. Paramagnetic relaxation enhancements pinpoint viscosinamide near the water-lipid interface, with its orientation dictated by the amphipathic distribution of hydrophobic and hydrophilic residues. Finally, the experimental observations are supported by molecular dynamics simulations. Thus a firm structural basis is now available for interpreting biophysical and bioactivity data relating to this class of compounds.


Assuntos
Lipopeptídeos/química , Simulação de Dinâmica Molecular , Peptídeos Cíclicos/química , Conformação Proteica , Acetonitrilos/química , Ligações de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Espectroscopia de Ressonância Magnética , Soluções
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