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1.
J Chromatogr A ; 1720: 464808, 2024 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-38471298

RESUMO

Juices and beverages are produced by industry for long-distance distribution and shelf-stability, providing valuable nutrients. However, their nutritional value is often underestimated due to insufficient analytical methods. We have employed non-targeted analysis through a standardized analytical protocol, taking advantage of Data Independent Acquisition (DIA) technique and a novel Chromatographic Retention Behavior (CRB) data deconvolution algorithm. After analyzing 9 fruits and their products, correlations between fruits and their juices are accurately digitalized by similarities of their LC-MS fingerprints. We also specify non-targeted molecules primarily associate with nutrient loss in these analyzed juice products, including nitrogenous nutrients, flavonoids, glycosides, and vitamins. Moreover, we unveiled previously unreported fruit-characteristic metabolites, of which reconstituted-from-concentrate (RFC) juices contain over 40% of the content found in their fresh counterparts. Conclusively, our method establishes a quantitative benchmark for rational selection of RFC juices to substitute natural fruits.


Assuntos
Bebidas , Frutas , Frutas/química , Bebidas/análise , Flavonoides/análise , Sucos de Frutas e Vegetais/análise
2.
Anal Chem ; 95(19): 7503-7511, 2023 05 16.
Artigo em Inglês | MEDLINE | ID: mdl-37130068

RESUMO

Accurate discrimination and classification of unknown species are the basis to predict its characteristics or applications to make correct decisions. However, for biogenic solutions that are ubiquitous in nature and our daily lives, direct determination of their similarities and disparities by their molecular compositions remains a scientific challenge. Here, we explore a standard and visualizable ontology, termed "biogenic solution map", that organizes multifarious classes of biogenic solutions into a map of hierarchical structures. To build the map, a novel 4-dimensional (4D) fingerprinting method based on data-independent acquisition data sets of untargeted metabolomics is developed, enabling accurate characterization of complex biogenic solutions. A generic parameter of metabolic correlation distance, calculated based on averaged similarities between 4D fingerprints of sample groups, is able to define "species", "genus", and "family" of each solution in the map. With the help of the "biogenic solution map", species of unknown biogenic solutions can be explicitly defined. Simultaneously, intrinsic correlations and subtle variations among biogenic solutions in the map are accurately illustrated. Moreover, it is worth mentioning that samples of the same analyte but prepared by alternative protocols may have significantly different metabolic compositions and could be classified into different "genera".


Assuntos
Metabolômica , Metabolômica/métodos
3.
Virol Sin ; 37(4): 591-600, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35688418

RESUMO

Pseudorabies virus (PRV), an etiological agent of pseudorabies in livestock, has negatively affected the porcine industry all over the world. Epithelial cells are reported as the first site of PRV infection. However, the role of host proteins and its related signaling pathways in PRV replication is largely unclear. In this study, we performed a quantitative phosphoproteomics screening on PRV-infected porcine kidney (PK-15) epithelial cells. Totally 5723 phosphopeptides, corresponding to 2180 proteins, were obtained, and the phosphorylated states of 810 proteins were significantly different in PRV-infected cells compared with mock-infected cells (P â€‹< â€‹0.05). GO and KEGG analysis revealed that these differentially expressed phosphorylated proteins were predominantly related to RNA transport and MAPK signaling pathways. Further functional studies of NF-κB, transcription activator factor-2 (ATF2), MAX and SOS genes in MAPK signaling pathway were analyzed using RNA interference (RNAi) knockdown. It showed that only ATF2-knockdown reduces both PRV titer and viral genome copy number. JNK pathway inhibition and CRISPR/Cas9 gene knockout showed that ATF2 was required for the effective replication of PRV, especially during the biogenesis of viral genome DNA. Subsequently, by overexpression of the ATF2 gene and point mutation of the amino acid positions 69/71 of ATF2, it was further demonstrated that the phosphorylation of ATF2 promoted PRV replication. These findings suggest that ATF2 may provide potential therapeutic target for inhibiting PRV infection.


Assuntos
Fator 2 Ativador da Transcrição/metabolismo , Herpesvirus Suídeo 1 , Pseudorraiva , Animais , Células Epiteliais , Herpesvirus Suídeo 1/genética , Proteômica , Suínos , Replicação Viral
4.
Anal Chem ; 93(36): 12273-12280, 2021 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-34459594

RESUMO

Sequential window acquisition of all theoretical spectra (SWATH) as a typical data-independent acquisition (DIA) strategy is favorable for untargeted metabolomics. It could theoretically acquire product ions of all precursor ions, including precursor ions showing chromatographic peaks of rather poor qualities. However, existing data processing methods present limited capabilities in capturing poor-quality peaks of precursor ions. Thus, although their product ions could be acquired, their precursor ions are absent. Here, we present a new strategy, chromatographic retention behavior-SWATH (CRB-SWATH), that could unbiasedly capture poor-quality peaks and provide high resolutions of multiplexed mass spectroscopy (MS/MS) spectra in SWATH datasets. CRB-SWATH monitors CRBs of SWATH-MS signals under a series of altered elution gradients. As signals of compounds differ from noise by showing CRBs, both the precursor and fragment ions are captured, while ignoring their peak qualities. Moreover, CRB-SWATH offers good chances to resolve highly multiplexed MS/MS spectra in SWATH datasets because precursor ions coeluted in a single elution gradient often present different CRBs. In the untargeted metabolic analysis of Hela cell extracts, CRB-SWATH showed the advantage in exclusively capturing 2645 ions of poor-quality peaks (i.e., tiny peaks, discontinuous ion traces, tailing peaks, zigzag peaks, etc.), accounting for 34.4% of all the untargeted precursor ions extracted. Therein, it is noteworthy that among 2116 negative ions detected in hydrophilic interaction liquid chromatography (HILIC) mode, 1284 poor-quality ion peaks (>60%) were exclusively captured by CRB-SWATH. As CRB-SWATH automatically captures a large sum of true ion peaks of poor qualities, extracts MS/MS spectra of high purities, and provides chromatographic retention behaviors of untargeted metabolites for identification and classification, it could be a useful metabolomics tool for understanding biological phenomena better.


Assuntos
Fenômenos Biológicos , Espectrometria de Massas em Tandem , Cromatografia Líquida , Células HeLa , Humanos , Íons
5.
Virology ; 553: 70-80, 2021 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-33242760

RESUMO

Many viruses utilize molecular chaperone heat shock protein 90 (Hsp90) for protein folding and stabilization, however, the role of Hsp90 in herpesvirus lifecycle is obscure. Here, we provide evidence that Hsp90 participates in pseudorabies virus (PRV) replication. Viral growth kinetics assays show that Hsp90 inhibitor geldanamycin (GA) abrogates PRV replication at the post-penetration step. Transmission electron microscopy demonstrates that dysfunction of Hsp90 diminishes the quantity of PRV nucleocapsids. Overexpression and knockdown of Hsp90 suggest that de novo Hsp90 is involved in PRV replication. Mechanismly, dysfunction of Hsp90 inhibits PRV major capsid protein VP5 expression. Co-immunoprecipitation and indirect immunofluorescence assays indicate that Hsp90 interacts with VP5. Interestingly, Hsp70, a collaborator of Hsp90, also interacts with VP5, but doesn't affect PRV growth. Finally, inhibition of Hsp90 results in PRV VP5 degradation in a proteasome-dependent manner. Collectively, our data suggest that Hsp90 contributes to PRV virion assembly and replication via stabilization of VP5.


Assuntos
Proteínas do Capsídeo/metabolismo , Proteínas de Choque Térmico HSP90/metabolismo , Herpesvirus Suídeo 1/fisiologia , Montagem de Vírus , Animais , Benzoquinonas/farmacologia , Proteínas do Capsídeo/química , Linhagem Celular , Herpesvirus Suídeo 1/crescimento & desenvolvimento , Herpesvirus Suídeo 1/ultraestrutura , Humanos , Lactamas Macrocíclicas/farmacologia , Nucleocapsídeo/ultraestrutura , Complexo de Endopeptidases do Proteassoma/metabolismo , Ligação Proteica , Dobramento de Proteína , Estabilidade Proteica , Suínos , Vírion/crescimento & desenvolvimento , Vírion/fisiologia , Replicação Viral/efeitos dos fármacos
6.
J Chromatogr A ; 1578: 45-52, 2018 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-30343818

RESUMO

A fast and sensitive ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UHPLC-ESI-MS/MS) method was developed for simultaneously analyzing 10 phthalates in perfume, which are forbidden by the hygienic standards for cosmetics in China (2007 edition). Matrix effect is significant on a phthalate when it is co-eluted with other phthalates. Improving the resolution between adjacent phthalate peaks is found effective in reducing the matrix effects. Thus, simultaneous analysis of the 10 phthalates requires successful resolutions of each phthalate. Nonetheless, a trade-off between the resolution and analysis time results either incomplete separation or prolonged analysis time. Here, the UHPLC elution gradient is optimized considering the predicted retention time of each phthalate. The resolutions and matrix effects of targeted compounds are evaluated to determine the optimal elution gradient for UHPLC-MS analysis method. Under the optimized gradient, the resolution between closest phthalate peaks is beyond 1.7, while the analysis time is merely 7 min. Except for dimethyl phthalate (DMP) and dicyclohexyl phthalate (DCHP), insignificant matrix effects have been found on all the phthalates. Direct quantifications through external calibration curve are appropriate for such analytes. Nonetheless, DMP and DCHP suffering obvious matrix effects require extra analyses of spiked samples for the quantifications through the standard addition method. Instrumental limits of quantitation (iLOQs) are 0.12-89 µg L-1 for the targeted phthalates. Meanwhile, the accuracy and precision of the analytical method are good. Finally, the forbidden phthalates in 26 sampled perfumes are successfully analyzed by the developed method.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Líquida de Alta Pressão , Perfumes/química , Ácidos Ftálicos/análise , Espectrometria de Massas em Tandem , China , Ácidos Ftálicos/química
7.
Chemistry ; 24(43): 10979-10983, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-29873120

RESUMO

Covalent organic frameworks (COF) are complex functional systems constructed with atomic precision by linking well-defined building blocks through robust covalent bonds. ß-cyclodextrin (ß-CD) is a most employed supramolecule which bears a hydrophobic cavity guiding molecular specific recognitions. Building COF with asymmetric ß-CD linkers is challenging and has never been reported. Here, ß-CD COF is grown with heptakis(6-amino-6-deoxy)-ß-CD and terephthalaldehyde in green solvents of water and ethanol at room temperature. The COF is characterized by powder X-ray diffraction, which matches well with the simulated crystal structure. Weaving ß-CD into a framework through reticular chemistry allows the integration of a large amount of ß-CD units (50 mol %), much higher than ß-CD polymers. The ß-CD COF has larger surface area, more uniform pore size, and higher thermal stability than the non-crystalline ß-CD polymer produced by the same reagents. Finally, the ß-CD COF holds abundant specific interaction sites enabling selective molecular adsorption.

8.
J Chromatogr A ; 1547: 21-28, 2018 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-29555357

RESUMO

A mixed-mode polymer monolithic column functionalized by arsonic acid groups was prepared by single-step in situ copolymerization of monomers p-methacryloylaminophenylarsonic acid (p-MAPHA) and pentaerythritol triacrylate (PETA). The prepared poly(p-MAPHA-co-PETA) monolithic column has a homogeneous monolithic structure with good permeability and mechanical stability. Zeta potential measurements reveal that the monolithic stationary phase holds a negative surface charge when the mobile phase resides in the pH range of 3.0-8.0. The retention mechanisms of prepared monolithic column are explored by the separation of selected polycyclic aromatic hydrocarbons (PAHs), nucleosides, and three basic compounds. The results indicate that the column functions in three different separation modes associated with reversed-phase chromatography based on hydrophobic interaction, hydrophilic interaction chromatography, and cation-exchange chromatography. The column efficiency of prepared monolithic column is estimated to be 70,000 and 76,000 theoretical plates/m for thiourea and naphthalene, respectively, at a linear flow velocity of 0.85 mm/s using acetonitrile/H2O (85/15, v/v) as the mobile phase. Furthermore, an analysis of the retention factors obtained for the PAHs indicates that the prepared monolithic column exhibits good reproducibility with relative standard deviations of 2.9%, 4.0%, and 4.7% based on run-to-run injections, column-to-column preparation, and batch-to-batch preparation, respectively. Finally, we investigate the separation performance of the proposed monolithic column for select phenols, sulfonamides, nucleobases and nucleosides.


Assuntos
Arsenicais/química , Cromatografia Líquida/métodos , Polímeros/síntese química , Acetonitrilas/química , Acrilatos/síntese química , Acrilatos/química , Cátions , Cromatografia por Troca Iônica , Cromatografia de Fase Reversa , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Nucleosídeos/isolamento & purificação , Fenóis/isolamento & purificação , Polimerização , Polímeros/química , Propilenoglicóis/síntese química , Propilenoglicóis/química , Reprodutibilidade dos Testes , Sulfonamidas/isolamento & purificação
9.
Talanta ; 176: 344-349, 2018 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-28917760

RESUMO

Monitoring the concentration of blood glucose in patients is a key component of good medical diagnoses. Therefore, developing an accurate, rapid and sensitive strategy for monitoring blood glucose is of vital importance. We proposed a strategy for serum glucose determination combining 2-(4-boronobenzyl) isoquinolin-2-ium bromide chemical labeling with black phosphorus assisted laser desorption ionization-time of flight mass spectrometry (CL-BP/ALDI-TOF MS). The entire analytical process consisted of 1min of protein precipitation and 3min of chemical labeling in a microwave oven prior to the BP/ALDI-TOF MS analysis. The analysis can be completed in 5min with high throughput and extremely low sample consumption. Good linearity for glucose was obtained with a correlation coefficient (R) of 0.9986. The limit of detection (LOD) and limit of quantification (LOQ) were 11.5 fmol and 37.5 fmol, respectively. Satisfied reproducibility and reliability were gained by evaluation of the intra- and inter-day precisions with relative standard deviations (RSDs) less than 7.2% and relative recoveries ranging from 87.1% to 108.1%, respectively. The proposed strategy was also applied for the analysis of endogenous glucose in various serum samples and the results were consistent with those obtained using the hexokinase method in a clinical laboratory. Considering the results, the proposed CL-BP/ALDI-TOF MS strategy has proven to be reliable, fast, and sensitive for quantitative analysis of serum glucose.


Assuntos
Glicemia/análise , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Humanos , Lasers , Fósforo
10.
Talanta ; 170: 252-259, 2017 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-28501167

RESUMO

In this work, a polyoxometalate (POM) incorporated polymer monolith microextraction (PMME) was successfully proposed and employed in the selective extraction of basic antidepressants in undiluted urine sample. This hybrid monolith exhibited strong cation-exchange interaction (SCX) with positively charged antidepressants when pH was 3.0, because of the multiple ionizable moieties on polyanionic POM. As such, antidepressants in complex sample matrices were efficiently extracted by the monolith, and the matrix effect was significantly reduced. In addition, due to the high amount of anionic POM, the monolith exhibited remarkable extraction capacities for target antidepressants ranging from 4.7 to 5.8mg/g. Further, the POM incorporated PMME was coupled with high-performance liquid chromatography-ultraviolet (HPLC-UV). Thus, antidepressants in undiluted urine sample was efficiently extracted under optimized extraction conditions online. The limits of detection (LODs) for the target antidepressants ranged from 0.7 to 1.4ng/mL, and the linear range was 5-1000ng/mL with determination coefficients (R2) higher than 0.9960. The recoveries ranged from 86.8% to 104.0% with relative standard deviations (RSDs) of 0.4-10.1%. The proposed procedure was successfully applied to determine antidepressant in human urine. Taken together, the developed method presented a new strategy for the analysis of basic drugs in undiluted urine sample, which could be used for monitoring medicines in pharmacokinetic analysis.


Assuntos
Antidepressivos/urina , Cromatografia Líquida de Alta Pressão/métodos , Microextração em Fase Sólida/métodos , Compostos de Tungstênio/química , Adsorção , Antidepressivos/isolamento & purificação , Humanos , Limite de Detecção
11.
J Chromatogr A ; 1499: 30-37, 2017 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-28390667

RESUMO

Phosphorylation is a crucial post-translational modification, which plays pivotal roles in various biological processes. Analysis of phosphopeptides by mass spectrometry (MS) is intractable on account of their low stoichiometry and the ion suppression from non-phosphopeptides. Thus, enrichment of phosphopeptides before MS analysis is indispensable. In this work, we employed pyridoxal 5'-phosphate (PLP), as an immobilized metal affinity chromatography (IMAC) ligand for the enrichment of phosphopeptides. PLP was grafted onto several substrates such as silica (SiO2), oxidized carbon nanotube (OCNT) and silica coated magnetic nanoparticles (Fe3O4@SiO2). Then the metal ions Fe3+, Ga3+ and Ti4+ were incorporated for the selective enrichment of phosphopeptides. It is indicated that Fe3O4@SiO2-PLP-Ti4+ has a superior selectivity towards phosphopeptides under as much as 1000-fold interferences of non-phosphopeptides. Further, Fe3O4@SiO2-PLP-Ti4+ exhibited high efficiency in selective enrichments of phosphopeptides from complex biological samples, including human serum and tryptic digested non-fat milk. Finally, Fe3O4@SiO2-PLP-Ti4+ was successfully employed in the sample pretreatment for profiling phosphopeptides in a tryptic digest of rat brain proteins. Our experimental results evidenced a great potential of this new chelator-based material in phosphoproteomics study.


Assuntos
Cromatografia de Afinidade/métodos , Fosfatos/química , Fosfopeptídeos/isolamento & purificação , Animais , Humanos , Íons , Magnetismo , Espectrometria de Massas , Metais , Nanopartículas/análise , Fosfopeptídeos/química , Processamento de Proteína Pós-Traducional , Piridoxal/química , Ratos , Dióxido de Silício/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
12.
J Colloid Interface Sci ; 496: 465-473, 2017 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-28257965

RESUMO

Pd-nitrogen-doped-carbon nanocatalysts (Pd-C/N) with different morphologies, such as porous spheres, yolk-shell and hollow structures, had been synthesized and compared. The yolk-shell Pd-nitrogen-doped-carbon nanocatalysts (YS-Pd-C/N) and hollow Pd-nitrogen-doped-carbon nanocatalysts (H-Pd-C/N) were prepared through different etch time using SiO2 spheres as hard-templates. The as-prepared catalysts were characterized thoroughly by TEM, BET, XRD, FT-IR, and XPS. Importantly, the catalysts have moderate BET specific surface area in the range from 200 to 300m2g-1 and pore volume between 0.2 and 0.3cm3g-1. The reduction of 4-nitrophenol is chosen as a model reaction to research the morphology effects of these prepared Pd-C/N catalysts with the same chemical compositions. Interestingly, H-Pd-C/N exhibited the best catalytic performance, which could be attributed to its high nitrogen content, the uniform distribution of abundant active sites, as well as the synergistic effect of graphitic C/N shell and Pd species for the catalytic reaction. Especially, the unique hollow morphology and porous shell of H-Pd-C/N made it to be a nanoreactor, which was beneficial to improve the catalytic activities. In addition, H-Pd-C/N nanocatalysts exhibited favorable stability in the recycling reactions.

13.
Mikrochim Acta ; 185(1): 43, 2017 12 08.
Artigo em Inglês | MEDLINE | ID: mdl-29594396

RESUMO

The authors have immobilized nanowires made from zirconium glycerolate (ZrGly) on magnetite (Fe3O4) nanoparticles by applying a solvothermal growth process using metal-glycerolate as a precursor. The structure and the dissolution-recrystallization mechanism of the resulting Fe3O4@ZrGly composite were investigated by attenuated total reflection-FTIR, energy-dispersive X-ray analysis, thermogravimetric analysis and solid-state cross polarization/magic angle spinning 13C NMR spectroscopy. The interaction between the zirconium glycerolate in Fe3O4@ZrGly and cis-diols leads to efficient adsorption of riboncleosides which then can be quantified by HPLC with UV detection. The sorbent was successfully applied to the selective enrichment of adenosine, cytidine, uridine and guanosine from spiked human urine samples. The detection limit of the method is in the range from 1.7 to 19 ng·mL-1 of nucleosides in spiked human urine, with relative standard deviations of lower than 12.4% and recoveries ranging from 90.6 to 113%. Graphical abstract Fe3O4@ZrGly with high selectivity towards ribonucleosides was designed and applied for quantitation of urinary ribonucleosides.


Assuntos
Nanopartículas de Magnetita/química , Nanofios/química , Ribonucleosídeos/isolamento & purificação , Zircônio/química , Adsorção , Glicerol/química , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção , Tamanho da Partícula , Ribonucleosídeos/urina , Microextração em Fase Sólida/métodos , Propriedades de Superfície
14.
Anal Biochem ; 477: 21-7, 2015 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-25700866

RESUMO

The preparation of biocatalysts based on immobilized trypsin is of great importance for both proteomic research and industrial applications. Here, we have developed a facile method to immobilize trypsin on hydrophobic cellulose-coated silica nanoparticles by surface adsorption. The immobilization conditions for the trypsin enzyme were optimized. The as-prepared biocatalyst was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and elemental analysis. In comparison with free enzyme, the immobilized trypsin exhibited greater resistances against thermal inactivation and denaturants. In addition, the immobilized trypsin showed good durability for multiple recycling. The general applicability of the immobilized trypsin for proteomic studies was confirmed by enzymatic digestion of two widely used protein substrates: bovine serum albumin (BSA) and cytochrome c. The surface adsorption protocols for trypsin immobilization may provide a promising strategy for enzyme immobilization in general, with great potential for a range of applications in proteomic studies.


Assuntos
Celulose/química , Interações Hidrofóbicas e Hidrofílicas , Nanopartículas/química , Proteólise , Tripsina/química , Tripsina/metabolismo , Animais , Bovinos , Estabilidade Enzimática , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Proteômica , Dióxido de Silício/química , Temperatura
15.
Anal Chim Acta ; 853: 608-616, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-25467510

RESUMO

A hydrophilic interaction liquid chromatography (HILIC) method was developed to measure the composition of humic substances from river, reservoir, and treated wastewater based on their physicochemical properties. The current method fractionates the humic substances into four well-defined groups based on parallel analyses with a neutral and a cationic HILIC column, using mobile phases of varied compositions and pH. The results indicate that: (i) the proportion of carboxylic acids in the humic substances from terrestrial origins is less than half of that from treated wastewater (Jeddah, KSA), (ii) a higher content of basic compounds was observed in the humic substances from treated wastewater and Ribou Reservoir (Cholet, France) than in the sample from Loire River (France), (iii) a higher percentage of hydrophobic macromolecules were found in the humic substances from Loire River than in the other samples, and (iv) humic substances of treated wastewater contained less ionic neutral compounds (i.e., pKa 5-9) than the waters from terrestrial origins. The physicochemical property disparity amongst the compounds in each humic substances sample was also evaluated. The humic substances from the lightly humic Loire river displayed the highest disparity, whereas the highly humic Suwannee river (Georgia, USA) showed the most homogeneous humic substances.

16.
J Mass Spectrom ; 49(2): 154-60, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24464543

RESUMO

The composition and physiochemical properties of aquatic-phase natural organic matter (NOM) are most important problems for both environmental studies and water industry. Laser desorption/ionization (LDI) mass spectrometry facilitated successful examinations of NOM, as humic and fulvic acids in NOM are readily ionized by the nitrogen laser. In this study, hydrophobic NOMs (HPO NOMs) from river, reservoir and waste water were characterized by this technique. The effect of analytical variables like concentration, solvent composition and laser energy was investigated. The exact masses of small molecular NOM moieties in the range of 200-1200 m/z were determined in reflectron mode. In addition, spectra of post-source-decay experiments in this range showed that some compounds from different natural NOMs had the same fragmental ions. In the large mass range of 1200-15,000 Da, macromolecules and their aggregates were found in HPO NOMs from natural waters. Highly humic HPO exhibited mass peaks larger than 8000 Da. On the other hand, the waste water and reservoir water mainly had relatively smaller molecules of about 2000 Da. The LDI-MS measurements indicated that highly humic river waters were able to form large aggregates and membrane foulants, while the HPO NOMs from waste water and reservoir water were unlikely to form large aggregates.


Assuntos
Benzopiranos/análise , Substâncias Húmicas/análise , Espectrometria de Massas/métodos , Rios/química , Águas Residuárias/química , Benzopiranos/química , Monitoramento Ambiental
17.
Analyst ; 138(22): 6737-41, 2013 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-24045409

RESUMO

Natural occurring organic compounds from food, natural organic matter, as well as metabolic products have received intense attention in current chemical and biological studies. Examination of unknown compounds in complex sample matrices is hampered by the limited choices for data readout and molecular elucidation. Herein, we report a generic method of hydrophilic interaction chromatography (HILIC) coupled with matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the rapid characterization of ingredients in pharmaceutical compounds, tea, and coffee. The analytes were first fractionated using a cationic HILIC column prior to MALDI-MS analyses. It was found that the retention times of a compound arising from different samples were consistent under the same conditions. Accordingly, molecules can be readily characterized by both the mass and chromatographic retention time. The retention behaviors of acidic and basic compounds on the cationic HILIC column were found to be significantly influenced by the pH of mobile phases, whereas neutral compounds depicted a constant retention time at different pH. The general HILIC-MALDI-MS method is feasible for fast screening of naturally occurring organic compounds. A series of homologs can be determined if they have the same retention behavior. Their structural features can be elucidated by considering their mass differences and hydrophilic properties as determined by HILIC chromatogram.


Assuntos
Técnicas de Química Analítica/instrumentação , Café/química , Compostos Orgânicos/análise , Preparações Farmacêuticas/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Chá/química , Interações Hidrofóbicas e Hidrofílicas
18.
Anal Chim Acta ; 718: 121-9, 2012 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-22305907

RESUMO

Two covalently bonded cationic ß-CD chiral stationary phases (CSPs) prepared by graft polymerization of 6(A)-(3-vinylimidazolium)-6-deoxyperphenylcarbamate-ß-cyclodextrin chloride or 6(A)-(N,N-allylmethylammonium)-6-deoxyperphenylcarbamoyl-ß-cyclodextrin chloride onto silica gel were successfully applied in high-performance liquid chromatography (HPLC). Their enantioseparation capability was examined with 12 racemic pharmaceuticals and 6 carboxylic acids. The results indicated that imidazolium-containing ß-CD CSP afforded more favorable enantioseparations than that containing ammonium moiety under normal-phase HPLC. The cationic moiety on ß-CD CSPs could form strong hydrogen bonding with analytes in normal-phase liquid chromatography (NPLC) to enhance the analytes' retention and enantioseparations. In reversed-phase liquid chromatography (RPLC), the analytes exhibited their maximum retention when the pH of mobile phase was close to their pK(a) value. Inclusion complexation with CD cavity and columbic/ionic interactions with cationic substituent on the CD rim would afford accentuated retention and enantioseparations of the analytes.


Assuntos
Ácidos Carboxílicos/isolamento & purificação , Cromatografia Líquida de Alta Pressão/métodos , Preparações Farmacêuticas/isolamento & purificação , Sílica Gel/química , beta-Ciclodextrinas/química , Cátions/química , Cromatografia de Fase Reversa/métodos , Polimerização , Estereoisomerismo
19.
J Chromatogr A ; 1224: 97-103, 2012 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-22236564

RESUMO

Cationic ß-cyclodextrin (CD) perphenylcarbamoylated derivatives were chemically bonded onto vinylized silica using a radical co-polymerization reaction. The derived materials were used as chiral stationary phases (CSP) in supercritical fluid chromatography (SFC). Enantioseparations were successfully demonstrated on 14 racemates encompassing flavanones, thiazides and amino acid derivatives. The electrostatic force between the analytes and the cationic moiety on ß-CD derivative was found to be important for retention and enantioseparation of the racemates. Aromatic cationic moiety on ß-CD enabled better enantioseparations than aliphatic cationic moiety. It was also found that the presence of acid additives would result in lower retention of the analytes but often assist the chiral resolutions.


Assuntos
Cromatografia com Fluido Supercrítico/métodos , beta-Ciclodextrinas/química , Aminoácidos/análise , Aminoácidos/química , Cátions/química , Flavanonas/análise , Flavanonas/química , Líquidos Iônicos , Eletricidade Estática , Estereoisomerismo , Tiazidas/análise , Tiazidas/química
20.
J Chromatogr A ; 1203(2): 185-92, 2008 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-18684460

RESUMO

Four cationic beta-cyclodextrin derivatives, namely mono-6-(3-methylimidazolium)-6-deoxy-perphenylcarbamoyl-beta-cyclodextrin chloride (MPCCD), mono-6-(3-methylimidazolium)-6-deoxyper(3,5-dimethylphenylcarbamoyl)-beta-cyclodextrin chloride (MDPCCD), mono-6-(3-octylimidazolium)-6-deoxyperphenylcarbamoyl-beta-cyclodextrin chloride (OPCCD) and mono-6-(3-octylimidazolium)-6-deoxyper(3,5-dimethylphenylcarbamoyl)-beta-cyclodextrin chloride (ODPCCD), have been synthesized and physically coated onto porous spherical silica gel to obtain novel chiral stationary phases (CSPs). The performances of these CSPs are studied on high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) using 18 racemic aryl alcohols as test analytes. Among these four CSPs, OPCCD shows the best separation results for all analytes on both HPLC and SFC analyses. Chromatographic studies reveal that the CSPs consisting of an n-octyl group on the imidazolium moiety and phenylcarbamoyl groups on the cyclodextrin ring provide enhancement of analyte-chiral substrate interactions over CSPs bearing the methyl group on the imidazolium moiety and 3,5-dimethylphenylcarbamoyl groups on the cyclodextrin ring.


Assuntos
Cromatografia Líquida de Alta Pressão/instrumentação , Cromatografia com Fluido Supercrítico/instrumentação , beta-Ciclodextrinas/síntese química , Estereoisomerismo
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