Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 49.663
Filtrar
1.
J Agric Food Chem ; 67(38): 10800-10812, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31490681

RESUMO

In this work, a highly efficient pesticide residue screening and quantification method was established using ultrahigh-performance liquid chromatography-tandem quadrupole time-of-flight mass spectrometry based on in-source fragmentation. Over 400 pesticides were tested, among which 96 pesticides displayed in-source fragmentation. A novel concept of in-source fragment fraction was proposed to evaluate the extent of in-source fragmentation, which was found to be chemical structure- and source parameter-dependent. A high-resolution MS/MS library containing 403 pesticides and 126 fragments was created and was applied for library searching of pesticide residues in vegetables and fruits. The introduction of in-source fragments effectively circumvented misannotation and occurrence of false negatives. The quantification ability for the fragments was validated in terms of recovery, linearity, and limit of quantification and its superiority to the parent pesticides was established. Finally, the proposed method was applied for the analysis of real samples and proficiency test samples, and false negative results were successfully avoided in the analysis.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Frutas/química , Resíduos de Praguicidas/química , Espectrometria de Massas em Tandem/métodos , Verduras/química , Contaminação de Alimentos/análise , Limite de Detecção
2.
J Agric Food Chem ; 67(38): 10791-10799, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31497956

RESUMO

Very weak signals of fragment ions of nosiheptide could be observed using liquid chromatography-tandem mass spectrometry. The preparation of 4-hydroxymethyl-3-methyl-1H-indole-2-carboxylic acid (HMIA), a specific fragment of nosiheptide, by alkaline hydrolysis is described. HMIA showed a good mass spectrometric signal in negative electrospray ionization mode. In the new method, the nosiheptide residue in muscle tissue was hydrolyzed with sodium hydroxide aqueous solution; this was followed by cleanup using mixed mode cartridges. Identification and quantification of nosiheptide were carried out by analyzing HMIA in hydrolysate of muscles. Nosiheptide showed a good linear relationship (r > 0.996) in the calibration range of 2-500 µg/kg, and a low limit of quantification of 2 µg/kg was obtained in swine, chicken, and fish muscles. Recoveries of nosiheptide from spiked muscle samples were 85-108% with relative standard deviations less than 10%. The proposed method was successfully applied for the detection of the nosiheptide residue in medicated animal tissues samples.


Assuntos
Antibacterianos/química , Cromatografia Líquida de Alta Pressão/métodos , Resíduos de Drogas/química , Contaminação de Alimentos/análise , Carne/análise , Espectrometria de Massas em Tandem/métodos , Álcalis/química , Animais , Galinhas , Peixes , Hidrólise , Limite de Detecção , Músculos/química , Suínos , Tiazóis/química
3.
J Agric Food Chem ; 67(33): 9362-9370, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31368700

RESUMO

This manuscript presents an effective and robust method for simultaneous stereoselective determination of two pyrethroid insecticides, tetramethrin and α-cypermethrin in different food products by high-performance liquid chromatography. Enantioseparation was carried out using reversed-phase chromatography, and the influences of four polysaccharide-based chiral columns, mobile phase composition, and column temperature on retention were fully investigated. Satisfactory separation was obtained on Chiralpak IG column using acetonitrile-water (75:25, v/v) under isocratic conditions. To extract and purify the target analytes from food matrices, matrix solid-phase dispersion was employed with C18 as dispersant and primary secondary amine as well as graphitized carbon black as cleanup sorbents. Response surface method based on Box-Behnken design was implemented to assist optimization of the extraction variables. Then, method validation was done in real samples including specificity, linearity, sensitivity, trueness, precision, as well as stability, and its analytical performance fulfills the criteria recommended by the European Union SANTE/11945/2015, demonstrating its applicability in studying the stereochemistry of chiral tetramethrin and α-cypermethrin in food products.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Grão Comestível/química , Frutas/química , Inseticidas/química , Piretrinas/química , Verduras/química , Cromatografia de Fase Reversa/métodos , Contaminação de Alimentos/análise , Inseticidas/isolamento & purificação , Piretrinas/isolamento & purificação , Extração em Fase Sólida , Estereoisomerismo
4.
An Acad Bras Cienc ; 91(3): e20180621, 2019 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-31411258

RESUMO

Aristolochia triangularis Cham., is one of the most frequently used medicinal plant in Southern Brazil. Preparations containing the leaves and/or stems are traditionally used as anti-inflammatory, diuretic, as well as antidote against snakebites. This study screened A. triangularis extracts, fractions and isolated compounds for different bioactivities. A weak antiproliferative activity against human lung cancer cell line (A549) was observed only for chloroform fraction obtained from stems (CFstems - CC50: 2.93 µg/mL). Also, a moderate antimicrobial activity against Staphylococcus aureus was detected just for chloroform fraction obtained from leaves (CFleaves -13-16 mm inhibition zone). Additionally, two semi-purified fractions (CFstems-4 and CFleaves-4) selectively inhibited HSV-1 replication (IC50 values of 0.40 and 2.61 µg/mL, respectively), while only CFleaves showed promising results against Leishmania amazonensis. Fractionation of extracts resulted in the isolation of one neolignan (-) cubebin and one lignan (+) galbacin. However, these compounds are not responsible for the in vitro bioactivities herein detected. The presence of aristolochic acid I and aristolochic acid II in the crude ethanol extract of stems (CEEstems) and leaves (CEEleaves) was also investigated. The HPLC analysis of these extracts did not display any peak with retention time or UV spectra comparable to aristolochic acids I and II.


Assuntos
Aristolochia/química , Compostos Fitoquímicos/química , Antibacterianos/farmacologia , Antifúngicos/farmacologia , Antiprotozoários/farmacologia , Antivirais/farmacologia , Ácidos Aristolóquicos/química , Brasil , Fracionamento Químico , Cromatografia Líquida de Alta Pressão/métodos , Humanos , Compostos Fitoquímicos/farmacologia , Extratos Vegetais/farmacologia
5.
Environ Monit Assess ; 191(8): 525, 2019 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-31363866

RESUMO

Arsenic contamination in marine environments is a serious issue because some arsenicals are very toxic, increasing the health risks associated with the consumption of marine products. This study describes the development of an improved rapid method for the quantification of arsenic species, including arsenite (AsIII), arsenate (AsV), arsenocholine (AsC), arsenobetaine (AsB), dimethylarsinic acid (DMA), and monomethyl arsonic acid (MMA), in seaweed, sediment, and seawater samples using high-performance liquid chromatography/inductively coupled plasma-mass spectrometry (HPLC/ICP-MS). ICP-MS based on dynamic reaction cells was used to eliminate spectral interference. Ammonium nitrate- and phosphate-based eluents were used as the mobile phases for HPLC analysis, leading to shorter overall retention time (6 min) and improved peak separation. Arsenicals were extracted with a 1% HNO3 solution that required no clean-up process and exhibited reasonable sensitivity and peak resolution. The optimized method was verified by applying it to hijiki seaweed certified reference material (CRM, NMIJ 7405-a) and to spiked blank samples of sediment and seawater. The proposed method measured the concentration of AsV in the CRM as 9.6 ± 0.6 µg/kg dry weight (dw), which is close to the certified concentration (10.1 ± 0.5 µg/kg dw). The recovery of the six arsenicals was 87-113% for the sediment and 99-101% for the seawater. In the analysis of real samples, AsV was the most abundant arsenical in hijiki and gulfweed, whereas AsB was dominant in other seaweed species. The two inorganic arsenicals (AsIII and AsV) and AsV were the most dominant in the sediment and seawater samples, respectively.


Assuntos
Arsenicais/análise , Cromatografia Líquida de Alta Pressão/métodos , Monitoramento Ambiental/métodos , Espectrometria de Massas/métodos , Poluentes Químicos da Água/análise , Monitoramento Ambiental/instrumentação , Sedimentos Geológicos/química , República da Coreia , Água do Mar/química , Alga Marinha/química
6.
Chem Commun (Camb) ; 55(70): 10456-10459, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31411211

RESUMO

A bio-orthogonal chemistry-based approach for fluorescent labelling of ribosomal RNA is described. It involves an adenosine analogue modified with trans-cyclooctene and masked 5'-phosphate group using aryl phosphoramidate. The incorporation into rRNA has been confirmed using agarose gel electrophoresis, as well as a highly sensitive UHPLC-MS/MS method. Fluorescent labelling of rRNA has been achieved in live HeLa cells via an inverse electron demand Diels-Alder reaction with a tetrazine conjugated to an Oregon Green fluorophore. This communication describes the stepwise approach that led to the development and characterization of the probe. The results demonstrate a new strategy towards development of future fluorescent probes to investigate the biochemistry of nucleic acids.


Assuntos
Corantes Fluorescentes/química , RNA Ribossômico/química , Cromatografia Líquida de Alta Pressão/métodos , Reação de Cicloadição , Células HeLa , Humanos , Espectrometria de Massas em Tandem/métodos
7.
J Agric Food Chem ; 67(32): 9088-9095, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31347836

RESUMO

Triclocarban (TCC) and triclosan (TCS) have been simultaneously detected in five kinds of foodstuffs using an immunoaffinity purification method coupled with ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) for the first time. Two highly specific monoclonal antibodies against TCC and TCS were produced and coupled to N-hydroxysuccinimide-activated Sepharose 6B gel to prepare the immunosorbent. Under the optimal conditions, mean recoveries from spiked samples by the IAC-UHPLC-MS/MS method were 70.1-92.8% for TCC and 76.6-102.5% for TCS. Intraday relative standard deviations were below 14.5%. The limits of quantification (LOQs) of TCC were 1 ng/L for beverage samples and 0.01-0.02 µg/kg for food samples. The LOQs of TCS were 0.03 µg/L for beverage samples and 0.2-0.3 µg/kg for food samples. The applicability of the method has been proven by analyzing TCC and TCS in different samples from supermarkets in Beijing. The proposed method is sufficiently sensitive and reliable for monitoring trace concentrations of TCC and TCS in food samples.


Assuntos
Antibacterianos/análise , Carbanilidas/análise , Cromatografia de Afinidade/métodos , Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas em Tandem/métodos , Triclosan/análise , Antibacterianos/isolamento & purificação , Bebidas/análise , Carbanilidas/isolamento & purificação , Contaminação de Alimentos/análise , Técnicas de Imunoadsorção , Triclosan/isolamento & purificação
8.
J Agric Food Chem ; 67(32): 8773-8782, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31283205

RESUMO

Conquering rapid postripeness and deterioration of Agaricus bisporus is quite challenging. We previously observed that methyl jasmonate (MeJA) pretreatment postponed the deterioration of A. bisporus, but the mechanism is unknown. Here, a nontargeted metabolomics analysis by ultrahigh-pressure liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS/MS) revealed that MeJA increased the synthesis of malate by inhibiting the decomposition of fumarate and cis-aconitate. MeJA maintained energy supply by enhancing ATP content and energy charge level and improving hexokinase and glucose-6-phosphate dehydrogenase activities as well. These results promoted ATP supply by maintaining glycolysis, the TCA cycle, and the pentose phosphate pathway. In addition, we revealed that the delayed deterioration was attributed to MeJA treatment which stimulated the energy status of A. bisporus by reducing the respiration rate and nutrient decomposition, thus maintaining energy production. Our results provide a new insight into the role of MeJA treatment in delaying deterioration of A. bisporus through ATP production and supply.


Assuntos
Acetatos/farmacologia , Agaricus/efeitos dos fármacos , Agaricus/metabolismo , Ciclopentanos/farmacologia , Oxilipinas/farmacologia , Ácido Aconítico/metabolismo , Trifosfato de Adenosina/metabolismo , Agaricus/química , Agaricus/crescimento & desenvolvimento , Cromatografia Líquida de Alta Pressão/métodos , Metabolismo Energético/efeitos dos fármacos , Fumaratos/metabolismo , Malatos/metabolismo , Metabolômica , Espectrometria de Massas em Tandem/métodos
9.
J Agric Food Chem ; 67(31): 8599-8608, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31287302

RESUMO

Because foods are perceived through combined inputs from taste and odor, which are determined by the concentration of the individual odor and taste molecules, the unified high-throughput quantitation of volatile odorants and non-volatile tastants with the very same instrumental setup has been a long-standing but yet unmet dream. The research presented here for the first time demonstrates, after only minimal sample workup, the highly accurate, rapid, and sensitive unified quantitation of odorants and tastants of key flavor molecules in apple juice on a single ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) platform over a large dynamic range of up to 6 orders of magnitude. While flavor-active aldehydes, ketones, and organic acids were analyzed after derivatization with 3-nitrophenylhydrazine, taste-active polyphenols and odor-active esters were directly analyzed by means of UHPLC-MS/MS with and without target analyte enrichment through stir-bar sorptive extraction. This "unified flavor quantitation" approach holds promise to accelerate the transition of today's labor and time-consuming, low-throughput analysis of odorants and tastants into a new era of high-performance quantitation of key flavor molecules.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Aromatizantes/química , Ensaios de Triagem em Larga Escala/métodos , Odorantes/análise , Espectrometria de Massas em Tandem/métodos , Sucos de Frutas e Vegetais/análise , Malus/química , Compostos Orgânicos Voláteis/química
10.
J Agric Food Chem ; 67(31): 8677-8688, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31293164

RESUMO

Reversed-phase ultrahigh-performance-liquid chromatography-mass spectrometry (UPLC-MS) is the typical method for the lipidomic analysis of most of biological samples, which was rarely used for the comprehensive lipidomic analysis of marine shellfish. Thus, a range of columns, modifiers, and resuspension solvents were evaluated using UPLC-electrospray ionization-quadrupole time-of-flight-MS to facilitate the ionization efficiency in both the positive and negative electrospray ionization (ESI(+)/(-)) modes for abalone lipids. Optimal lipidomic coverage was acquired with 10 mM ammonium formate in both ESI(+)/(-) modes. The selected resuspension solvents also influenced ionization efficiency through the matrix effect, and resuspension in methanol enhanced the signal intensities by reducing ion suppression. Because of the higher glycerophospholipid content in shellfish, bridged ethylene hybrid C8 columns showed clear advantages over charged surface hybrid C18 columns. A series of glycerophospholipids, lyso-glycerophospholipids, glycerolipids, and fatty acids in different shellfish can be annotated and semiquantified in one injection by the optimized method.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Lipídeos/química , Frutos do Mar/análise , Espectrometria de Massas por Ionização por Electrospray/métodos , Animais , Cromatografia Líquida de Alta Pressão/instrumentação , Ácidos Graxos/química , Glicerofosfolipídeos/química , Espectrometria de Massas por Ionização por Electrospray/instrumentação , Espectrometria de Massas em Tandem
11.
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
12.
Chem Commun (Camb) ; 55(64): 9543-9546, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31334509

RESUMO

The novel Vial@FPBA strategy was established for a large-scale pharmacokinetic study of glycosides, during which glycosides were absorbed into a boronic acid-functionalized 96-well glass plate and directly desorbed for UHPLC-MS/MS analysis. Hence, specific and high-throughput glycoside enrichment was achieved simultaneously. The LODs were reduced up to 50 times compared to the case of the methanol method. Meanwhile, sample pre-processing time was greatly saved by skipping the protein sedimentation and supernatant concentration steps.


Assuntos
Ácidos Borônicos/química , Glicosídeos/farmacocinética , Ensaios de Triagem em Larga Escala/métodos , Cromatografia Líquida de Alta Pressão/métodos , Vidro , Limite de Detecção , Espectrometria de Massas em Tandem/métodos
13.
J Agric Food Chem ; 67(29): 8279-8289, 2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31259549

RESUMO

This study is focused on examining the tocopherol isomers (α-, γ-, and δ-) fingerprinting by online RP-HPLC analysis with post column detection using CUPRAC (cupric reducing antioxidant capacity) methodology for argan oil authenticity. The proposed online assay was validated with good precision, reproducibility, and linearity. Sixteen argan oil samples (100% pure-certified and other commercial argan oils), possible adulterating vegetable oils (i.e., olive, sunflower, corn, and soya oils), and virgin argan oil blended with olive, sunflower, corn, and soya oils at levels of 5%, 10%, 15%, and 20% were analyzed. Spectrophotometric CUPRAC, DPPH, and ABTS assays were applied. Discrimination of fraudulent argan oils from virgin samples was performed by utilizing orthogonal partial least-squares discriminant analysis (OPLS-DA) regression modeling with good sensitivity and specificity. We suggested [γ-toc/α-toc] value as a new first screening adulteration factor (AF) that could be used to assess fraudulent argan oil samples. The distinct decrement in AF value was observed by the increase of adulteration rate. The AF values for virgin argan oils were ranged from 11.8 (lower limit) to 18.6 (upper limit). The presence of ß-sitosterol detected in commercial argan oils (with AF values out of limit values) was evaluated as fraudulent which was in accordance with the proposed assay. Our method enabled the detection of argan oil samples at adulteration levels of >5% in the case of sunflower, olive, and soya oils, >15% in the case of corn oil. This method may be an alternative and specific assay for the authentication and quality detection of commercial argan oils.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Óleos Vegetais/análise , Análise Discriminante , Contaminação de Alimentos/análise , Análise dos Mínimos Quadrados , Reprodutibilidade dos Testes , Tocoferóis/análise
14.
J Agric Food Chem ; 67(28): 8035-8044, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31282154

RESUMO

The simultaneous detection of multiple mycotoxins is important due to the increased toxic effects of combined mycotoxins in grains. In this research, a combination of modified QuEChERS with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used for simultaneous detection of 20 mycotoxins in grains. A series of different types of magnetic (Fe3O4) nanoparticles modified with multiwalled carbon nanotubes (Fe3O4-MWCNTs) were designed as modified QuEChERS adsorbents for facile and efficient purification and for target interferences removal in the matrices. When there is an external magnetic field, the proposed modified QuEChERS method uses a shorter pretreatment time compared with the traditional QuEChERS method, which makes it possible to conduct high-throughput analyses. To optimize the QuEChERS process, the extraction solvent and the type and amount of the Fe3O4-MWCNTs were investigated. Under optimal conditions, the method was validated and showed satisfactory linearity (r2 ≥ 0.9965), good recovery (73.5-112.9%), good precision (1.3-12.7%), and excellent sensitivity (ranging from 0.0021 to 5.4457 ng g-1), which indicates that this method can be used for detecting multiple mycotoxins in real samples.


Assuntos
Carbono/química , Cromatografia Líquida de Alta Pressão/métodos , Grão Comestível/química , Micotoxinas/química , Micotoxinas/isolamento & purificação , Nanotubos/química , Extração em Fase Sólida/métodos , Espectrometria de Massas em Tandem/métodos , Adsorção , Magnetismo , Extração em Fase Sólida/instrumentação
15.
Food Chem ; 298: 125048, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260953

RESUMO

Heterocyclic aromatic amines (HAAs) are harmful by-products naturally formed during the heating process of foodstuffs. The present work reported an analytical method for HAAs analysis for the first time in bakery products by QuEChERS technique combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Bakery products were ultrasonically extracted with acetonitrile and sodium hydroxide solution (1 mmol/L). The obtained extracting solution was nearly dried under nitrogen stream and subsequently purified by QuEChERS technique using primary secondary amine (PSA) as adsorbents. Fourteen HAAs were separated on a C18 column with the mobile phase of a mixture of acetonitrile and 1 mmol/L ammonium acetate water solution (containing 0.04% acetic acid), and detected by MS/MS under multiple reaction monitoring (MRM) mode. The developed method was validated in terms of linearity, matrix effect, accuracy and precision. The method showed a good linearity (R2 > 0.999) for all analytes in their corresponding concentration ranges. The method limit of quantifications (LOQs, S/N = 10) of 14 HAAs were in the range of 0.3-4.5 µg/kg. The average recoveries (n = 6) at 3 spiked levels ranged from 62.8 to 96.8% with relative standard deviations (RSDs) of 1.2-7.6%. The validated method was applied in HAAs analysis in 20 bakery products and 4 kinds of HAAs (harman, norharman, AaC, PhIP) were detected with the concentrations ranging from 0.6 to 35.6 µg/kg.


Assuntos
Aminas/análise , Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas em Tandem/métodos , Aminas/química , Pão/análise , Compostos Heterocíclicos/química , Limite de Detecção , Reprodutibilidade dos Testes
16.
Food Chem ; 298: 125080, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260985

RESUMO

Propolis extract was investigated as potential substitute for sorbate in orangeade. Extract was prepared by using aqueous solution of hydroxypropyl-beta-cyclodextrins. Propolis extract was incorporated in non-carbonated orange soft drinks and its antioxidant activity, microbiological stability and color changes were estimated and compared to those of orangeade containing potassium sorbate. l-Ascorbic acid (AsA) degradation at concentrations 0.13 and 1.3% w/w was investigated in the presence of propolis during storage using High Performance Liquid Chromatography-Ion Exclusion Column (HPLC-IEC). The results indicate that the rate of degradation decreased with an increase in ascorbic acid concentration, while addition of propolis affected the degradation rate of samples containing a high AsA concentration. The antifungal effect of propolis extract, potassium sorbate and their combination was assayed. Results showed the inhibition of Aspergillus spp. and B. bruxellensis inhibited in low combined concentrations antimicrobials, while Aspergillus spp. and T. macrosporus were inhibited at 450 mg/g propolis extract.


Assuntos
Bebidas , Conservação de Alimentos/métodos , Conservantes de Alimentos/química , Própole/química , Anti-Infecciosos , Antifúngicos/farmacologia , Antioxidantes/química , Ácido Ascórbico/análise , Ácido Ascórbico/química , Aspergillus/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão/métodos , Cor , Microbiologia de Alimentos , Extratos Vegetais/química , Própole/farmacologia , Ácido Sórbico/farmacologia
17.
Food Chem ; 299: 125108, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31310914

RESUMO

Macroporous resins have been employed in the effective recovery of flavonoids from plants. In this study, S8 polar resins were used to recover flavonoids and procyanidins from lotus seedpods. Adsorption kinetics, isotherms, and thermodynamics studies revealed that the adsorption process involved physico-chemical interactions, including flavonoid-resin and flavonoid-flavonoid electrostatic interactions, π-π aromatic stacking, moderate and strong hydrogen bonding, and repulsive forces. These forces worked complementarily in adsorption, except for the repulsive force, which opposed the adsorption. Further, adsorption temperature determined the adsorption behavior, with multilayer adsorption enhancing adsorption capacity. In dynamic desorption tests, an acetone/water/acetic acid mixture (58.77: 39.34: 1.89) designed by the D-optimal design method was able to desorb 95.57% and 89.85% of total flavonoids and procyanidins, respectively, using less than two bed volumes of solvent. Ultra-performance liquid chromatography triple-time of flight/mass spectrometry (UPLC-TOF/MS) analysis showed that 26 flavonoids, including 5 procyanidins, were detected after the recovery.


Assuntos
Flavonoides/isolamento & purificação , Nelumbo/química , Resinas Sintéticas/química , Sementes/química , Adsorção , Cromatografia Líquida de Alta Pressão/métodos , Flavonoides/análise , Flavonoides/química , Ligações de Hidrogênio , Espectrometria de Massas , Proantocianidinas/análise , Proantocianidinas/química , Proantocianidinas/isolamento & purificação , Eletricidade Estática
18.
J Chromatogr A ; 1602: 386-396, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31285057

RESUMO

A comprehensive Collision Cross Section (CCS) library was obtained via Travelling Wave Ion Guide mobility measurements through direct infusion (DI). The library consists of CCS and Mass Spectral (MS) data in negative and positive ElectroSpray Ionisation (ESI) mode for 463 and 479 endogenous metabolites, respectively. For both ionisation modes combined, TWCCSN2 data were obtained for 542 non-redundant metabolites. These data were acquired on two different ion mobility enabled orthogonal acceleration QToF MS systems in two different laboratories, with the majority of the resulting TWCCSN2 values (from detected compounds) found to be within 1% of one another. Validation of these results against two independent, external TWCCSN2 data sources and predicted TWCCSN2 values indicated to be within 1-2% of these other values. The same metabolites were then analysed using a rapid reversed-phase ultra (high) performance liquid chromatographic (U(H)PLC) separation combined with IM and MS (IM-MS) thus providing retention time (tr), m/z and TWCCSN2 values (with the latter compared with the DI-IM-MS data). Analytes for which TWCCSN2 values were obtained by U(H)PLC-IM-MS showed good agreement with the results obtained from DI-IM-MS. The repeatability of the TWCCSN2 values obtained for these metabolites on the different ion mobility QToF systems, using either DI or LC, encouraged the further evaluation of the U(H)PLC-IM-MS approach via the analysis of samples of rat urine, from control and methotrexate-treated animals, in order to assess the potential of the approach for metabolite identification and profiling in metabolic phenotyping studies. Based on the database derived from the standards 63 metabolites were identified in rat urine, using positive ESI, based on the combination of tr, TWCCSN2 and MS data.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Mobilidade Iônica/métodos , Espectrometria de Massas/métodos , Metaboloma , Urina/química , Aminas/análise , Animais , Calibragem , Aprendizado de Máquina , Ratos , Padrões de Referência
19.
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
20.
Anal Chim Acta ; 1078: 200-211, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358220

RESUMO

The effect of the ionization in the RP-HPLC retention of 66 acid-base compounds, most of them drugs of pharmaceutical interest, is studied. The retention time of the compounds can be related to the pH measured in the mobile phase (pwsH) through the sigmoidal equations derived from distribution of the neutral and ionic forms of the drug into the stationary and mobile phases. Fitting of the obtained retention vs. pH profiles provides the retention times of the ionic and neutral forms and the pKa values of the drugs in the mobile phase (pwsKa). The obtained pwsKa values are linearly correlated to the pKa values in water (pwwKa) with two different correlations, one for neutral acids and another for neutral bases that reflect the different influence of the dielectric constant of the medium in ionization of acids and bases. The retention of the neutral species is well correlated to the octanol-water partition coefficient of the drugs as measure of the lipophilicity of the drug, which affects chromatographic retention. Also, the retention time of the ionized forms is related to the retention time of the neutral forms by two different linear correlations, one for anions and the other for cations. These last correlations point out the different retention behaviour of anions and cations: anions are less retained than cations of the same lipophilicity, as measured by the octanol-water partition coefficient of the neutral form. The different retention behaviour of anionic, cationic and neutral forms is confirmed by the hold-up times obtained from different approaches: pycnometry and retention times of anionic (KBr and KI) and neutral (DMSO) markers. Hold-up times obtained by pycnometric measurements agree with those obtained by retention of neutral markers (0.83-0.85 min), whereas hold-up time for anions is mobile phase pH dependent. At acidic pH it is similar to the hold-up time for neutral markers (0.83 min), but then it decreases with the increase of mobile phase pH to 0.65 min at pH 11. The decrease can be explained by the ionization of the silanols of the column and exclusion of anions by charge repulsion. Although not directly measured, the obtained retention data and correlations indicate hold-up time for cations are similar or slightly lower than hold-up time for neutral compounds (0.77-0.83 min). The model proposed and the correlations obtained can be very useful for its implementation in retention prediction algorithms for optimization of separation purposes.


Assuntos
Aminas/química , Ácidos Carboxílicos/química , Fenóis/química , Piridinas/química , Cromatografia Líquida de Alta Pressão/métodos , Cromatografia de Fase Reversa/métodos , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Modelos Químicos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA