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1.
J Chromatogr A ; 1625: 461334, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709359

RESUMO

A comprehensive study on the chiral separation of bupivacaine, mepivacaine, prilocaine and propanocaine with eight commercial polysaccharide-based chiral stationary phases (CSPs) in reversed phase conditions compatible with MS detection is performed. Methanol and acetonitrile are used as organic modifiers. Retention and resolution values obtained for each compound in the different CSPs and mobile phases are compared. The polysaccharide-based CSPs tested present different enantioselectivity towards the analytes. From the results, the experimental conditions for determining the enantiomers of bupivacaine, mepivacaine, prilocaine and propanocaine in saline aqueous samples using MS detection are used, for the first time, to perform an enantioselective biodegradability study.


Assuntos
Anestésicos Locais/isolamento & purificação , Cromatografia de Fase Reversa/métodos , Polissacarídeos/química , Acetonitrilos/química , Biodegradação Ambiental , Cromatografia Líquida de Alta Pressão , Metanol/química , Peso Molecular , Estereoisomerismo , Água/química
2.
J Chromatogr A ; 1624: 461218, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540066

RESUMO

In this study, amylose- and cellulose-phenylcarbamate-based chiral columns with different chiral-selector (CS) chemistries were compared to each other for the separation of enantiomers of basic chiral analytes in acetonitrile and aqueous-acetonitrile mobile phases in HPLC. For two chemistries the amylose-based columns with coated and immobilized CSs were also compared. The comparison of CSs containing only electron-donating or electron-withdrawing substituents with those containing both electron-donating and electron-withdrawing substituents showed opposite results for the studied set of chiral analytes in the case of amylose and cellulose derivatives. Along with the chemistry of CS the focus was on the behavior of polysaccharide phenylcarbamates in acetonitrile versus aqueous acetonitrile as eluents. In agreement with earlier results, it was found that in contrast to the commonly accepted view, polysaccharide phenylcarbamates do not behave as typical reversed-phase materials for basic analytes either. In the range of water content in the mobile phase of up to 20-30% v/v the behavior of these CSs is similar to hydrophilic interaction liquid chromatography (HILIC)-type adsorbents. This means that with increasing water content in the mobile phase up to 20-30% v/v, the retention of analytes mostly decreases. The important finding of this study is that the separation efficiency improves for most analytes when switching from pure acetonitrile to aqueous acetonitrile. Therefore, in spite of reduced retention, the separation of enantiomers improves and thus, the HILIC-range of mobile phase composition, offering shorter analysis time and better peak resolution, is advantageous over pure polar-organic solvent mode. Interesting examples of enantiomer elution order (EEO) reversal were observed for some analytes based on the content of water in the mobile phase on Lux Cellulose-1 and Lux Amylose-2 columns.


Assuntos
Amilose/química , Celulose/química , Cromatografia Líquida de Alta Pressão/métodos , Preparações Farmacêuticas/isolamento & purificação , Fenilcarbamatos/química , Acetonitrilos/química , Elétrons , Etanolaminas/análise , Etanolaminas/isolamento & purificação , Preparações Farmacêuticas/análise , Propanolaminas/análise , Propanolaminas/isolamento & purificação , Propranolol/análise , Propranolol/isolamento & purificação , Estereoisomerismo , Água/química
3.
Pestic Biochem Physiol ; 167: 104594, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32527433

RESUMO

The combined use of entomopathogenic fungi and sublethal rate of chemical insecticides or other biological control agents have been proposed as an environmentally and sustainable strategy in the control of locust pests. In this paper, the quarter and the half of the recommended dose of Metarhizium anisopliae var. acridum (» and ½ Ma) and the aggregation pheromone (Phenylacetonitrile: PAN) were applied simultaneously and sequentially to Schistocerca gregaria fifth-instar nymphs. In addition, the physiological effects of PAN on locusts were assessed at the behavior, immune response, and biochemical level by evaluating for glutathione-S-transferase (GST), acetylcholinesterase inhibition (AChE), and malondialdehyde accumulation (MDA). Results showed that simultaneous application of PAN and the entomopathogenic fungus exhibited additive interaction. Synergistic interaction was also demonstrated when nymphs were exposed to PAN first, then treated with M. anisopliae var. acridum. Behavioral bioassay revealed that fifth-instar nymphs avoided the PAN odour and tended to remain away from the stimulus cup. In the choice assay, the pheromone significantly repelled the locusts at 2, 4, and 6 h of exposure which selected the PAN-free arena chamber. Moreover, treated nymphs become hyperactive and disoriented as evidenced by the cumulative distance travelled and the trajectory of locusts during the experiment. Immunological studies showed that PAN significantly decreased the differential haemocyte counts (prohemocytes and plasmatocytes) with a dose-response relationship. Data of biochemical analyzes showed that the PAN exposure reduced the activity of acetylcholinesterase and induced significantly the glutathione S-transferases and MDA concentration in the desert locust fifth-instar nymphs. Moreover, transcriptomic responses to the PAN exposure were evaluated using gene expression levels of CYP540 and GST. The transcript levels showed an up-regulation in GST expression level particularly in nymphs exposed for 4 and 6 h. A significant increase in CYP450 transcript level was also observed after 2 h of exposure, which decreased significantly after 4 and 6 h.


Assuntos
Gafanhotos , Metarhizium , Acetonitrilos , Animais , Feromônios , Transcriptoma
4.
J Chromatogr A ; 1624: 461234, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540074

RESUMO

Atmospheric amines contribute to the nucleation and initial growth of new particles as well as secondary organic aerosol formation, influencing the radiative balance of the Earth's atmosphere. In this study, we develop an ion chromatography (IC) method for separating and quantifying the nine most abundant amines (methylaminium (MMAH+), dimethylaminium (DMAH+), trimethylaminium (TMAH+), ethylaminium (MEAH+), diethylaminium (DEAH+), propylaminium (MPAH+), butylaminium (MBAH+), ethanolaminium (MEOH+), and triethanolaminium (TEOH+)) from six common inorganic species in atmospheric aerosols. The retention times of the amines were altered by the addition of acetonitrile to the eluent because acetonitrile can reduce the adsorption of hydrophobic amines on the stationary phase. The developed method achieved the successful separation of DEAH+ and TMAH+ from inorganic cations, which often coelute with each other in established IC methods. The interference of K+ on the determination of MEAH+ was eliminated by the complexation of K+ with 18-crown-6, which prolonged the retention time of K+. Finally, 9 target amines and 6 common inorganic cations were separated, with a resolution Rs ≥ 1.2 for DEAH+ and MPAH+ and Rs > 1.5 for other species. The detection limits varied in the range of 0.34-1.48 ng for the 9 amines and 0.19-0.56 ng for the inorganic cations. The developed method was successfully applied for the determination of low molecular weight amines and inorganic cations in PM2.5 collected from an urban site in Shanghai and an isolated coast of Chongming Island. Eight amines were detected in the urban samples, in which MMAH+ and DMAH+ dominated. The average amine concentration in the urban aerosols was 76.3 ± 38.4 ng m-3, which is approximately 4-fold higher than those in the marine samples collected from the coast.


Assuntos
Acetonitrilos/química , Aminas/análise , Atmosfera/química , Cromatografia por Troca Iônica/métodos , Éteres de Coroa/química , Compostos Inorgânicos/análise , Aerossóis/análise , Cátions , China , Limite de Detecção , Padrões de Referência
5.
J Chromatogr A ; 1622: 461152, 2020 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-32376024

RESUMO

The chiral separations of small peptides is an important challenge in the biological and medical sciences, because different stereoisomers of chiral drugs can often possess different pharmacological, pharmacokinetic, and/or toxicological activities. Commercially available crown ether chiral stationary phases based on S-(3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 (CROWNPAK CR-I (+)) and (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (ChiroSil RCA (+)) have been successfully used for separating enantiomers of various racemic compounds containing primary amino groups. In this investigation, enantioresolution of more complex model analyte - tetrapeptide Tyr-Arg-Phe-Lys-NH2, has been reported on crown ether chiral stationary phases. Organic and acidic modifier content in aqueous mobile phase was tested. All Tyr-Arg-Phe-Lys-NH2 stereoisomers showed U-shaped retention plots, based on ACN content in mobile phase. Increased retention of tetrapeptide stereoisomers was observed at low (<35%) and at high (>70%) acetonitrile content in the mobile phase, indicating that different separation mechanisms are most likely involved. As a result, baseline separation of all eight tetrapeptide enantiomer pairs was achieved under isocratic elution mode on both chiral columns.


Assuntos
Éteres de Coroa/química , Peptídeos/química , Peptídeos/isolamento & purificação , Acetonitrilos/química , Padrões de Referência , Estereoisomerismo , Fatores de Tempo
6.
Artigo em Inglês | MEDLINE | ID: mdl-32361630

RESUMO

Ibotenic acid (IBA) is an amino acid and muscimol (MUS) is the decarboxyl derivative of IBA. They are mushroom neurotoxins with high polarity and low molecular weight. Only one transition (159->113 for IBA and 115->98 for MUS) can be found when directly measured by high performance liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). Therefore, the identification and quantification of trace amount of the toxins in biomaterial are difficult. A highly sensitive and accurate analytical method for IBA and MUS in plasma was developed by LC-MS/MS with the application of bimolecular dansylation and internal standard calibration. Acetonitrile was used for protein precipitation and for toxin extraction from plasma. The toxins and internal standards (L-tyrosine-13C9,15N for IBA and tyramine-d4 for MUS) were derivatized with dansyl chloride (DNSCl). The reaction conditions of the bimolecular dansylation were optimized and the fragmentation pathways of the derivatives in MS/MS were studied. Method validation was carried out according to the Bioanalytical Method Validation Guidance for Industry (FDA, USA, 2018). The limits of detection for IBA and MUS in plasma were 0.3 ng mL-1 and 0.1 ng mL-1, respectively. The linear ranges in plasma were 1-500 ng mL-1 and 1-200 ng mL-1 with the correlation coefficients of 0.998 and 0.999 for IBA and MUS, respectively. The recoveries at three spiked levels were 90.7-111.4% with relative standard deviations (RSDs) of 6.4-10.3% for IBA and the results were 85.1-94.2% with RSDs of 5.0-8.9% for MUS. The toxin levels in patients' plasma samples under different poisoning degree were presented.


Assuntos
Agaricales/química , Ácido Ibotênico/sangue , Muscimol/sangue , Neurotoxinas/sangue , Espectrometria de Massas em Tandem/métodos , Acetonitrilos/química , Cromatografia Líquida de Alta Pressão , Compostos de Dansil/química , Humanos , Limite de Detecção , Padrões de Referência , Reprodutibilidade dos Testes
7.
Chemosphere ; 256: 126994, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32445996

RESUMO

Dichloroacetonitrile (DCAN) is one of the most toxic and common nitrogenous disinfection by-products in water treatment. It is necessary to understand how this compound can be removed. In this study, the effectiveness of vacuum ultraviolet (VUV) at 185 nm was evaluated to destroy DCAN. When water is exposed to VUV, hydroxyl radicals (HO•), hydrogen atoms (H•), and hydrated electrons (eaq-) are generated. The individual contributions of these reactive species to DCAN degradation were distinguished using multiple scavengers. The results showed that eaq- was the most important species for DCAN degradation. The second-order rate constant for eaq- reacting with DCAN was calculated to be 3.16 × 1010 M-1s-1 using a quantitative structure-activity relationship (QSAR) method adopted from previous study, and determined to be 3.76 (±0.02) × 1010 M-1s-1 by competition kinetics. Although dissolved oxygen (DO) at 8 mg/L consumed 86% eaq-, the rest of eaq- still led to 93% removal of DCAN within 20 min. Chloride was the major inorganic product of DCAN degradation, while nitrate and nitrite were minor products. Quantum chemical calculation and mass balance calculation under an oxygen free condition further suggested that cleavage of C-Cl bonds was the major pathway by eaq- attack. This study demonstrated the significant role of eaq- in micropollutant destruction during VUV treatment.


Assuntos
Acetonitrilos/metabolismo , Poluentes Químicos da Água/metabolismo , Cloro , Desinfecção , Elétrons , Radical Hidroxila/química , Cinética , Nitratos , Nitrogênio , Fotólise , Raios Ultravioleta , Vácuo , Poluentes Químicos da Água/análise , Purificação da Água/métodos
8.
Food Chem ; 328: 127134, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32473493

RESUMO

An efficient single quadrupole gas chromatography with mass spectrometry method was developed and validated for the determination of indoxacarb residues in tomato and soil. Residues were extracted from the samples using acetonitrile as extracting solvent and the extracts were purified through primary secondary amine and graphitized carbon black. Recoveries were obtained in the range of 92.12-110.51% with the relative standard deviation of 1.32-4.32%. Indoxacarb dissipated with half-life of 3.12-3.21 and 1.24-1.35d for tomato and soil, respectively following doses of indoxacarb 14.5% SC at 60, 90 and 120 g.a.i./ha. Safe waiting periods were found to be 1-3d. The residues were removed from tomato fruit was in the range of 16.73 to 54.32% using simple decontamination approaches. The present study suggest that the use of indoxacarb in tomato at recommended dose, does not seem to pose any dietary risk to the consumers. The soil RQ values indicated low level of risk to earthworms and arthropods.


Assuntos
Contaminação de Alimentos/análise , Lycopersicon esculentum/química , Oxazinas/análise , Resíduos de Praguicidas/análise , Poluentes do Solo/análise , Acetonitrilos/química , Exposição Dietética , Análise de Alimentos/métodos , Cromatografia Gasosa-Espectrometria de Massas , Meia-Vida , Humanos , Índia , Oxazinas/metabolismo , Medição de Risco , Poluentes do Solo/metabolismo , Solventes/química , Fatores de Tempo
9.
Food Chem ; 327: 127015, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32434124

RESUMO

A simple and reliable analytical method was established for the simultaneous determination of tiafenacil and its six metabolites in fruits. The method involves three steps: extraction using acidified acetonitrile, clean-up by octadecylsilane(C18) and graphitized carbon black (GCB), and detection using liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). The method was validated on seven matrices spiked at 10, 100 and 1000 µg kg-1. Average recoveries ranged from 73% to 105% with intra-day RSDr (n = 5) of 1.0%-13.0% and inter-day RSDR (n = 15) of 1.1%-14.6%. Good linearities (R2 > 0.9911) were obtained for seven analytes in all matrices. The limit of quantification (LOQs) for tiafenacil and its six metabolites were 10 µg kg-1 in all matrices. This analytical method provides a basis for the establishment of maximum residue limits (MRL) and for the monitoring of tiafenacil residues in fruits.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Contaminação de Alimentos/análise , Frutas/química , Herbicidas/análise , Espectrometria de Massas em Tandem/métodos , Acetonitrilos/química , Fracionamento Químico , Análise de Alimentos/métodos , Herbicidas/metabolismo , Limite de Detecção , Reprodutibilidade dos Testes
10.
J Chromatogr A ; 1621: 461050, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32265050

RESUMO

Consumption of ciguatoxin-contaminated seafood can lead to ciguatera poisoning (CP). The diagnosis of CP in humans is based on the clinical symptoms after eating the fish from tropical or subtropical areas because no confirmatory clinical tests are available. One of the challenges for ciguatoxin analysis is their extremely low but toxicologically relevant concentration in biological samples. We previously reported a method using acetonitrile to precipitate proteins and extract the ciguatoxins simultaneously in whole blood samples from animals for toxin quantification by N2A cell-based assay. However, a test method for unambiguous confirmation of exposure of marine animals or humans to ciguatoxins is still needed. In the present study, we adopted the acetonitrile extraction method and added sample clean-up in the sample preparation for the determination of Pacific ciguatoxins CTX1B (aka P-CTX-1), 52-epi-54-deoxyCTX1B (aka P-CTX-2), and CTX3C (aka P-CTX-3C) in blood plasma by LC-MS/MS. We investigated sample clean-up, LC mobile phases, LC solvent programming, and settings of the two mass spectrometers (4000 Q TRAP and AB SCIEX Triple Quad 5500) in order to improve the ability to detect the Pacific ciguatoxins at ppt level. Rat blood plasma was used for the method development. Average recoveries of the three toxins in the rat plasma samples ranged from 90% to 116% with relative standard deviations of less than 15%. The method detection limits were still not low enough for the determination of the Pacific ciguatoxins in individual blood samples from Hawaiian monk seals with the two LC-MS systems. The methods were applied to a pooled sample of blood plasma collected from Hawaiian monk seals for confirmation of toxin exposure. This study will benefit monitoring of Pacific ciguatoxins in marine mammals and potentially humans by LC-MS/MS.


Assuntos
Cromatografia Líquida/métodos , Ciguatoxinas/sangue , Espectrometria de Massas em Tandem/métodos , Acetonitrilos/química , Animais , Limite de Detecção , Ratos , Focas Verdadeiras/sangue , Solventes
11.
Environ Sci Process Impacts ; 22(3): 653-662, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-32150177

RESUMO

The use of monochloramine as an alternative disinfectant to chlorine in drinking water treatment can lead to increased formation of emerging nitrogenous halogenated disinfection by-products (DBPs), even when the formation of regulated halogenated DBPs has decreased. In this study, we investigated formation of the semivolatile haloacetonitriles (HANs) from model nitrogen-containing compounds (6 amines, 1 amide, 6 amino acids, and 2 nitrogen-containing aromatic chemicals) and natural organic matter (NOM) reference materials after chloramination. In agreement with previous studies, most amino acids formed dichloroacetonitrile (DCAN). Additionally, DCAN formed from two amines containing aromatic rings (N,N-dimethylaniline and 3-(dimethylamino-methyl)indole) and the two nitrogen-containing aromatic chemicals (cotinine and phenytoin). This is the first report of DCAN formation from these precursors. DCAN also formed after chloramination of NOM reference materials, with the highest formation from the NOM material with the highest aromaticity. The results provide new evidence of a DCAN formation pathway from cleavage of activated aromatic structures after electrophilic substitution of chlorine and addition of monochloramine to the ring system. In particular, the results suggest that the previously proposed aldehyde pathway from the amino acid group is not responsible for the majority of DCAN formation from amino acids with an activated aromatic ring system. This newly proposed formation pathway for DCAN from activated aromatic organic matter has significant implications for NOM removal during water treatment to minimise DBP formation. Studies using 15N-labelled monochloramine showed that there was significant incorporation of nitrogen from monochloramine into DCAN, demonstrating that monochloramine disinfection promotes the formation of HANs.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Acetonitrilos , Cloro , Desinfecção , Halogenação , Água
12.
J Chromatogr A ; 1621: 461006, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32156459

RESUMO

This paper reports an optimized multiresidue extraction strategy based on the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction procedure and on solid-phase microextraction (SPME) for the simultaneous screening of 120 pesticides, 16 polycyclic aromatic hydrocarbons, and 22 polychlorinated biphenyls from the terrestrial snail Helix aspersa. The optimized extraction method was based on QuEChERS using acetonitrile, followed by dispersive-Solid-phase extraction clean-up using primary secondary amine and octadecyl (C18) sorbents. The obtained extracts were analyzed by liquid chromatography coupled with tandem mass spectrometry and gas chromatography coupled with tandem mass spectrometry. This latest technique was preceded by a pre-concentration step using SPME with appropriate fibers. Afterwards, the method was validated for its linearity, sensitivity, recovery, and precision. Results showed high sensitivity, accuracy, and precision, with limits of detection and quantification lower than 20 ng g - 1 for most considered pollutants. Both inter and intra-day analyses revealed low relative standard deviation (%), which was lower than 20% for most targeted compounds. Moreover, the obtained regression coefficient (R2) was higher than 0.98 and the recoveries were higher than 60% for the majority of the assessed pollutants.


Assuntos
Poluentes Ambientais/análise , Caracois Helix/química , Resíduos de Praguicidas/análise , Bifenilos Policlorados/análise , Acetonitrilos , Animais , Cromatografia Líquida/métodos , Biomarcadores Ambientais , Poluentes Ambientais/isolamento & purificação , Cromatografia Gasosa-Espectrometria de Massas/métodos , Resíduos de Praguicidas/isolamento & purificação , Bifenilos Policlorados/isolamento & purificação , Hidrocarbonetos Policíclicos Aromáticos/análise , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação , Microextração em Fase Sólida , Espectrometria de Massas em Tandem/métodos
13.
J Chromatogr A ; 1618: 460851, 2020 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-32008826

RESUMO

Mixed-mode cation-exchange stationary phases are useful for the separation of mixtures containing hydrophobic, acidic, and basic molecules. To ensure that weak organic bases are protonated and carboxylic acids are neutral low pH mobile phases are required. Mixed-mode stationary phases that are stable at pH < 3 are needed. We synthesized a crosslinked structure along the surface of thiol functionalized silica gel particles using the thiol-yne click reaction. The alkyne, 1,7-octadiyne, was added to the 3-mercaptopropyl silica gel, then crosslinked using 1,6-hexanedithiol. Elemental analysis showed low octadiyne ligand surface coverage, but, stoichiometrically, three sulfurs were added to each octadiyne ligand during the crosslinking step, indicating that crosslinking occurred. The effect of the crosslinking on the stability was tested with a 50:50 (v/v) pH 0.50 5% TFA aqueous:acetonitrile mobile phase at 70 °C for six days, over 35,000 column volumes. The stationary phase showed good stability with the retention of triphenylene decreasing only 20% during that time. The Tanaka test showed that the phase has a methylene selectivity of 1.20 ± 0.04, a high shape selectivity of 2.71 ± 0.03, and a 3.98 ± 0.05 cation-exchange factor at pH 2.70. The phase has a selectivity factor for nitrobenzene and benzene of 1.41 ± 0.01, indicating the electron donating charge transfer characteristic of the phase. The mixed-mode characteristics of the phase were investigated using a mixture of the monoamine neurotransmitters norepinephrine, dopamine, and serotonin. Baseline resolution of the monoamines could be obtained using a simple 20 mM potassium phosphate (pH 2.70)/methanol mobile phase. Altering both the methanol content and the potassium ion concentration altered the retention of the monoamines indicating mixed-mode cation exchange characteristic of the crosslinked stationary phase.


Assuntos
Química Click/métodos , Compostos de Sulfidrila/química , Acetonitrilos/química , Benzeno/química , Cátions , Cromatografia por Troca Iônica , Intervalos de Confiança , Elétrons , Elementos , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Neurotransmissores/análise , Nitrobenzenos/química , Ácido Trifluoracético/química , Água
14.
Environ Sci Technol ; 54(6): 3245-3255, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32068383

RESUMO

Sunlight plays an important role in transforming effluent organic matter as wastewater effluents travel downstream, but the corresponding effects on the formation of haloacetonitriles (HANs), a group of toxic disinfection byproducts, in wastewater-impacted surface water have not been thoroughly investigated. In this study, we observed that sunlight preferentially attenuated the formation potential of bromochloroacetonitrile (BCAN-FP) over that of dichloroacetonitrile (DCAN-FP) in chlorine- and UV-disinfected secondary effluents. For four effluent samples from different plants, 36 h of irradiation by simulated sunlight removed 28-33% of DCAN-FP and 41-48% of BCAN-FP. Across a larger set of effluent samples (n = 18), 8 h of irradiation (equivalent to 2-3 d of natural sunlight) decreased the calculated cytotoxicity contributed by dihaloacetonitrile-FP in most samples. Similar behavior was observed for a mixture of wastewater and surface water (volume ratio 1:1). For UV-disinfected effluents, the higher the UV dose, the more likely was there a reduction in DCAN-FP and BCAN-FP in the subsequent sunlight irradiation. Experiments with model compounds showed that fulvic acid and UV photoproducts of tryptophan yield excited triplet-state organic matters during sunlight irradiation and play an important role in promoting the attenuation of HAN precursors.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Acetonitrilos , Desinfecção , Luz Solar , Águas Residuárias
15.
J Chromatogr A ; 1619: 460939, 2020 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-32085912

RESUMO

Glyphosate (Glyp) and glufosinate (Gluf) are widely used herbicides around the world, and their effects on human health and detection of levels have drawn increasing attention. The present study was to establish a method to determine the contents of Glyp and Gluf from corn using multi-walled carbon nanotubes (MWCNTs) followed by ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). The corn samples were purified by MWCNTs, then the analytes reacted with 9-fluorenylmethylchloroformate (FMOCCl) of acetonitrile solution (20.0 g/L) at 50 °C water bath in a borate buffer solution (50.0 g/L, pH=9) to generate FMOC derivative products. After the derivatization, HSS T3 was used as the separation column, with acetonitrile and 0.05% ammonia as the mobile phase, and multiple reaction monitoring (MRM) mode with negative electrospray ionization (ESI-) was adopted. The validation parameters showed good verification results, with both of their quantitative limits (LOQ) as 0.005 mg/kg, recoveries between 90.3% and 95.4%, intra-day relative standard deviations (RSDs) in the ranges of 1.24% and 3.35%, and inter-day RSDs between 3.56% and 6.06%. The analytical method, developed in this study, has high accuracy and sensitivity, and is suitable for the simultaneous detection of Glyp and Gluf in corn.


Assuntos
Aminobutiratos/análise , Cromatografia Líquida de Alta Pressão , Análise de Alimentos/métodos , Glicina/análogos & derivados , Espectrometria de Massas em Tandem , Zea mays/química , Acetonitrilos/química , Fluorenos/química , Glicina/análise , Herbicidas/análise , Nanotubos de Carbono/química , Reprodutibilidade dos Testes
16.
J Chromatogr A ; 1619: 460971, 2020 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-32089289

RESUMO

When cyclodextrins (CDs) are used in chromatography analytes' retention time is decreased with an increase in concentration of CD in the mobile phase. Thus complex stability constants can be determined from the change in retention time of the ligand molecule upon complexation. Since the preceding approach implies extensive and time-consuming HPLC experiments, the goal of this research was to investigate the possibility of using in silico prediction tools instead. Quantitative structure-retention relationship (QSRR) model previously developed to explain the retention behavior of risperidone, olanzapine and their structurally related impurities in ß-CD modified HPLC system was applied to predict retention factor under different chromatographic conditions within the examined domains. Predicted retention factors were further used for calculation of stability constants and important thermodynamic parameters, namely standard Gibbs free energy, standard molar enthalpy and entropy, contributing to inclusion phenomenon. Unexpected prolonged retention with an increase in ß-CD concentration was observed, in contrast to the employed chromatographic theory used for the calculation of the stability constants. Consequently, it led to failure in stability constants and thermodynamic parameters calculation for almost all analytes when acetonitrile content was 20% (v/v) across the investigated pH range. Moreover, ionization of investigated analytes and free stationary phase silanol groups are pH dependent, leading to minimization of secondary interactions if free silanol groups are non-ionized at pH lower than 3. In order to prove accuracy of predicted retention factors, HPLC verification experiments were performed and good agreement between predicted and experimental values was obtained, confirming the applicability of proposed in-silico tool. However, the obtained results opened some novel questions and revealed that chromatographic method is not overall applicable in calculation of stability constants and thermodynamic parameters indicating the complexity of ß-CD modified systems.


Assuntos
Cromatografia Líquida de Alta Pressão , Modelos Teóricos , beta-Ciclodextrinas/química , Acetonitrilos/química , Entropia , Termodinâmica
17.
J Chromatogr A ; 1617: 460824, 2020 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-31980260

RESUMO

A tailor-made porous molecularly imprinted polymer (MIP) thin-film was prepared by in situ photo-radical polymerization on a glass slide and used as a microextraction adsorbent. Detection was carried out using gas chromatography-mass spectrometry (GC-MS) to afford a method suitable for the selective determination of trace concentrations of polycyclic aromatic sulfur heterocycles (PASHs) in seawater. PASHs are one of the most problematic aromatic organic pollutants, as they are considered more persistent and toxic compared to other analogous aromatic compounds in the environment. The optimized thin-film consisted of a 2-thiophenecarboxaldehyde pseudo-template with 1-vinylimidazole (1-Vim) as the functional monomer, bisphenol A dimethacrylate (BPADMA) as the cross-linker, acetonitrile as the porogen, and polyethylene glycol to boost porosity through formation of interpenetrating polymer networks. The adsorption behaviours of the thin-film, including adsorption kinetics, binding isotherms, and selectivity of MIP thin-film were investigated in detail. The highest imprinting factors (2.3-3.0) and adsorption capacity for targeted PASHs were achieved at a template:monomer:cross-linker ratio of 1:4:8. The method with no sample or film pretreatment showed very good reproducibility for the extraction of PASHs from spiked seawater samples (RSDs ≤ 6.0%, n = 3), was linear (R2 > 0.9960) over a range of 0.5-40 µg L-1, and gave limits of detection n the range of 0.029-0.166 µg L-1.


Assuntos
Impressão Molecular , Hidrocarbonetos Policíclicos Aromáticos/análise , Água do Mar/química , Poluentes Químicos da Água/análise , Acetonitrilos/química , Adsorção , Compostos Benzidrílicos/química , Cromatografia Gasosa-Espectrometria de Massas , Imidazóis/química , Metacrilatos/química , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação , Polietilenoglicóis/química , Polimerização , Polímeros/química , Porosidade , Reprodutibilidade dos Testes , Microextração em Fase Sólida , Enxofre , Poluentes Químicos da Água/isolamento & purificação
18.
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
19.
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
20.
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
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